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How To Make Your Gtir Rwd (for Free)

Dumb01

By Dumb01,
in Tutorials / DIY / FAQ

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Dumb01 Rookie

Dumb01

Posted
Posted

Thought I would post up the detail of my GTIR RWD conversion. It only cost me a carton plus quite a few hour of my life in labour so hopefully this will save someone some heartache!

Mine was a bit of a backyard job but having been driven pretty hard in RWD for a couple of months now, all seems to have worked. I actually think you are less likely to destroy your gearbox with this mod, given that the car is now capable of generating far less grip. You can also get away with a pretty sedate clutch setup for the same reason.

First point is figuring out how the 4wd system works and finding a free workshop manual.

This Japanese site has some trannie layout pictures:

http://www.niji.or.jp/home/g0873537/attesa.htm

post-53007-1276177804_thumb.jpg

While this website has a very useful online manual:

http://www.gtirworkshopmanual.com/

I would stay away from Nissan4U.com as I found their transmission drawings to be more confusing (and wrong) rather than usful.

Basically the mods involve:

• Lock (by welding) up the Centre diff

• Removing the front drive shafts

• Optionally removing the front diff/ input shaft, which I did to save weight and the effort of getting it to go back in.

• Install 40mm Welch plugs to seal gearbox/ transfer casing where front drive shafts originally exited.

I also put in a new clutch from Clutch and Brake Australia, apparently Exceedy brand, Single plate organic with heavier clamping than stock. Was about $300-350 and was delivered to my door at home within 2 hours for about $7 extra.

How the gearbox/Tranny works:

• The GTIR gearbox is basically the same as any FWD transverse gearbox setup however what would conventionally be the front diff driven off the gearbox is in this case the centre diff. this centre diff is also located to the front left as opposed to closer to the centre in a FWD car.

• The centre diff is basically a standard open diff with torsion LSD bolted in parallel to the open diff. Because of this you only need to weld up the open diff section to lock the diff. you can leave the torsion LSD where it is, it just becomes redundant.

• The transfer case is bolted to the side of the gearbox, this houses 2 independent circuits. At the front right it houses the front diff which is a simple open diff. The rest is the transfer which uses 2 perpendicular shafts to transfer drive by 90 degrees. The output from this drives the prop shaft.

• The Centre diff and Front diff are parallel to each other. 3 drive shafts run within each other to transfer drive.

• The 2 hollow shafts are the output shafts from the centre diff. The outer shaft is for the rear drive, the other hollow shaft in side of it is the drive to the front diff. The inside shaft id the drift shaft for the left front wheel, coming from the front diff.

• To complicate things further the outer hollow shaft that transfers the rear drive actually splits in 2 when you separate the transfer case from the gearbox. One half stays located in the transfer case by 2 bearings the other half stays attached to the centre diff in the gearbox.

• The other hollow shaft for transferring drive to the front diff is one piece and is permanently attached to the front diff. when you pull the front diff out this shaft comes with it.

• The front left drive shaft pull straight out like on a normal fwd car.

Gearbox/Trannie removal:

• The final aim here is to lock the centre diff by welding it

• The gearbox and trannie will both have to come off the first time. After that you should be able to only remove the gearbox should you have to change a clutch or do a gearbox rebuild.

• Some helpful info on removing the box/trannie can be found here.

http://www.sr20-forum.com/gtir/713-how-gti...ngine-situ.html

as well as in the workshop manual. Study the manual don't wing it like I tend to.

• Pull out the front drive shafts

• Undo the little bracket on the end of the transfer case that connects it to the engine block.

• Undo the end casing and pull it off, pull out the front diff/input shaft. You can do this later but u may as well do it at the start. If that's too hard stop now.

• Put the end casing back on to stop dust getting in. Undo all the transfer case and gearbox bolts. Some are a pain in the ass, ok the whole ordeal is a pain in the ass. Undo the engine mounts, they are easy and shift the engine forward if you need to get extra room behind the engine. See article above for more info.

• There are 1 or 2 bolts behind the engine hidden by the transfer case. You will have to drop the transfer case off first before you can get to the last 2 bolts and get the gearbox off. Leaving these to bolt off when it all goes together again will mean the gearbox can come off on its own.

• The transfer case can stay attached to the prop shaft but u will need to undo one of the prop shaft mounts. I did it this way as I was only going to strip the prop shaft nuts if I tried to undo them. Slop the trannie onto the ground.

• Pull the gearbox off it has heaps of clearance from the chassis rails etc. It will never come off with the 2 mystery bolts still attached, believe me I unknowingly tried.

Removing the diff from the gearbox:

• Unfortunately unlike the easy to get to front diff the getting to the centre diff means pulling the gearbox apart.

• Read the manual… and follow it..

• Get the gearbox on the bench undo all the bolts including the spring and ball retainers. Collect all the balls/ springs. Pull the casing apart and try not to smash the plastic oil guide, good luck, I doubt it is needed anyway : )

• With the case off have a look at everything. There is a ball bearing in the reverse selector just waiting to fall out. The manual shows where it goes back in.

• As per the manual you will need circlip removers to remove most of the selector folks off their rods and remove the reverse selector. The 3 selector arms drive 3 selector rods that drive the selector forks.

• The selector arms are driven by rod controlled by the shifter input.

• Have a play and try to understand how the gear selector works before undo circlips. This is a pain with no standard shift lever attached.

• There are 3 arms next to each other that go up and down to drive the different selector forks. A sliding and rotating rod selects the arms one at a time, depending which gear you want to pull.

• You want all the arms to line up, this is neutral. U should be able to slide the selector rod freely across all 3 selector arms. Jam the selector rod between 2 arms if you want to help keep the box in neutral, which you do.

• Undo the circlips as per the manual. There is a retaining pin on one folk but this can be left in, ignore the manual.

• There are a series of ball bearings that limit the movement of the selector rods. By pulling neutral these balls are out of the way and all rods are free to move. If not perfectly in neutral certain balls will lock and you will have endless trouble. With the circlips removed and in neutral you can pall the whole of the gearbox internals out momentarily and at the same time remove the diff. replace the gearbox internals.

• You can not remove the Diff on its own I have tried and failed.

• Installation is the exact reverse. Make sure u have neutral else the rod wont go in properly and you will have dramas. Took me about 10 hours looking at the inside of the gearbox to get this all right.

• When you go to put the case back on make sure the shims are aligned properly. If they are not you wont be able to shift cleanly or at all.

• Don't freak out if you put the whole car back together and cant shift gears. You can pull the gearbox casing off the gearbox when it is installed in the car and have a fiddle. Not ideal but relatively easy and saves the heartache of pulling everything apart again.

Locking the diff and reassembly:

• Once out the whole centre diff just unbolts.

• I contemplated a number of options. Besides machining a whole new assembly the best option is to weld the 4 inner of the open diff to each other and their shafts. This is more than sufficient, Avoid welding the output gears (especially the rear drive one) to the housing. This might seem stronger. Unwelded it has some play. Welded it wont and may distort, you may end up having bearing failure/ binding when you put everything back together.

• Only welding the 4 inner gears mean you don't have to remove any of the bearings or risk problematic distortion of the outer housing.

• Get as much oil off as you can. Its cas metal so use Stainless Steel tig rods, or specific rods for cast metals. Only takes 10 mins to weld.

• Test the alignment of the diff splines using the input shaft of the front diff. The torsion diff splines need to align with the welded diff splines. If they are slightly misaligned when back in the car the front diff will not go back in and you will have to leave it out. I say just leave it out either way.

• Bolt it all back together and put it back in the gearbox and in the car. Follow the workshop manual for doing up bolts etc.

• Leaving the front diff out means the gearbox oil and transfer oil will be shared. This may or may not matter to you. According to the manual they take different oils but in reality these days you can use the same oil on both.

• Make sure you seal up all the interfaces of the gearbox and trannie good and proper else they will leak. The interface between the transfer case and gearbox will now be full of oil now too where as originally it is not as far as I am aware.

• Put two 38 or 40?mm Welch plugs in the holes where the driveshafts were. These press in perfectly into the seals and don't really even need gluing or further retaining.

• You will need to keep the front hubs but pull the drive shafts out of them.

• The trannie is as much of a pain to install onto the gearbox as the gearbox is to install onto the engine. Leave the Y bracket etc off. From now on the transfer case can stay on, whenever the gearbox has to come off.

Hopefully this is of use. I will try and get some pictures up so that it makes a bit more sense.

At this point you will have a car pushing 300hp through the back wheels and what is apparently a torsion LSD in the back will act as an open diff. I have had no breakages. Car will spin up 4th gear in the wet and no longer has any understeer.

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  • 3 months later...
ltlrkt Newbie

ltlrkt

Posted
Posted

The standard split is 50/50 on the gtir.. My question is what percentage of the engines power is getting to the rear wheels with this setup?

Thought I would post up the detail of my GTIR RWD conversion. It only cost me a carton plus quite a few hour of my life in labour so hopefully this will save someone some heartache!

Mine was a bit of a backyard job but having been driven pretty hard in RWD for a couple of months now, all seems to have worked. I actually think you are less likely to destroy your gearbox with this mod, given that the car is now capable of generating far less grip. You can also get away with a pretty sedate clutch setup for the same reason.

First point is figuring out how the 4wd system works and finding a free workshop manual.

This Japanese site has some trannie layout pictures:

http://www.niji.or.jp/home/g0873537/attesa.htm

post-53007-1276177804_thumb.jpg

While this website has a very useful online manual:

http://www.gtirworkshopmanual.com/

I would stay away from Nissan4U.com as I found their transmission drawings to be more confusing (and wrong) rather than usful.

Basically the mods involve:

• Lock (by welding) up the Centre diff

• Removing the front drive shafts

• Optionally removing the front diff/ input shaft, which I did to save weight and the effort of getting it to go back in.

• Install 40mm Welch plugs to seal gearbox/ transfer casing where front drive shafts originally exited.

I also put in a new clutch from Clutch and Brake Australia, apparently Exceedy brand, Single plate organic with heavier clamping than stock. Was about $300-350 and was delivered to my door at home within 2 hours for about $7 extra.

How the gearbox/Tranny works:

• The GTIR gearbox is basically the same as any FWD transverse gearbox setup however what would conventionally be the front diff driven off the gearbox is in this case the centre diff. this centre diff is also located to the front left as opposed to closer to the centre in a FWD car.

• The centre diff is basically a standard open diff with torsion LSD bolted in parallel to the open diff. Because of this you only need to weld up the open diff section to lock the diff. you can leave the torsion LSD where it is, it just becomes redundant.

• The transfer case is bolted to the side of the gearbox, this houses 2 independent circuits. At the front right it houses the front diff which is a simple open diff. The rest is the transfer which uses 2 perpendicular shafts to transfer drive by 90 degrees. The output from this drives the prop shaft.

• The Centre diff and Front diff are parallel to each other. 3 drive shafts run within each other to transfer drive.

• The 2 hollow shafts are the output shafts from the centre diff. The outer shaft is for the rear drive, the other hollow shaft in side of it is the drive to the front diff. The inside shaft id the drift shaft for the left front wheel, coming from the front diff.

• To complicate things further the outer hollow shaft that transfers the rear drive actually splits in 2 when you separate the transfer case from the gearbox. One half stays located in the transfer case by 2 bearings the other half stays attached to the centre diff in the gearbox.

• The other hollow shaft for transferring drive to the front diff is one piece and is permanently attached to the front diff. when you pull the front diff out this shaft comes with it.

• The front left drive shaft pull straight out like on a normal fwd car.

Gearbox/Trannie removal:

• The final aim here is to lock the centre diff by welding it

• The gearbox and trannie will both have to come off the first time. After that you should be able to only remove the gearbox should you have to change a clutch or do a gearbox rebuild.

• Some helpful info on removing the box/trannie can be found here.

http://www.sr20-forum.com/gtir/713-how-gti...ngine-situ.html

as well as in the workshop manual. Study the manual don't wing it like I tend to.

• Pull out the front drive shafts

• Undo the little bracket on the end of the transfer case that connects it to the engine block.

• Undo the end casing and pull it off, pull out the front diff/input shaft. You can do this later but u may as well do it at the start. If that's too hard stop now.

• Put the end casing back on to stop dust getting in. Undo all the transfer case and gearbox bolts. Some are a pain in the ass, ok the whole ordeal is a pain in the ass. Undo the engine mounts, they are easy and shift the engine forward if you need to get extra room behind the engine. See article above for more info.

• There are 1 or 2 bolts behind the engine hidden by the transfer case. You will have to drop the transfer case off first before you can get to the last 2 bolts and get the gearbox off. Leaving these to bolt off when it all goes together again will mean the gearbox can come off on its own.

• The transfer case can stay attached to the prop shaft but u will need to undo one of the prop shaft mounts. I did it this way as I was only going to strip the prop shaft nuts if I tried to undo them. Slop the trannie onto the ground.

• Pull the gearbox off it has heaps of clearance from the chassis rails etc. It will never come off with the 2 mystery bolts still attached, believe me I unknowingly tried.

Removing the diff from the gearbox:

• Unfortunately unlike the easy to get to front diff the getting to the centre diff means pulling the gearbox apart.

• Read the manual… and follow it..

• Get the gearbox on the bench undo all the bolts including the spring and ball retainers. Collect all the balls/ springs. Pull the casing apart and try not to smash the plastic oil guide, good luck, I doubt it is needed anyway : )

• With the case off have a look at everything. There is a ball bearing in the reverse selector just waiting to fall out. The manual shows where it goes back in.

• As per the manual you will need circlip removers to remove most of the selector folks off their rods and remove the reverse selector. The 3 selector arms drive 3 selector rods that drive the selector forks.

• The selector arms are driven by rod controlled by the shifter input.

• Have a play and try to understand how the gear selector works before undo circlips. This is a pain with no standard shift lever attached.

• There are 3 arms next to each other that go up and down to drive the different selector forks. A sliding and rotating rod selects the arms one at a time, depending which gear you want to pull.

• You want all the arms to line up, this is neutral. U should be able to slide the selector rod freely across all 3 selector arms. Jam the selector rod between 2 arms if you want to help keep the box in neutral, which you do.

• Undo the circlips as per the manual. There is a retaining pin on one folk but this can be left in, ignore the manual.

• There are a series of ball bearings that limit the movement of the selector rods. By pulling neutral these balls are out of the way and all rods are free to move. If not perfectly in neutral certain balls will lock and you will have endless trouble. With the circlips removed and in neutral you can pall the whole of the gearbox internals out momentarily and at the same time remove the diff. replace the gearbox internals.

• You can not remove the Diff on its own I have tried and failed.

• Installation is the exact reverse. Make sure u have neutral else the rod wont go in properly and you will have dramas. Took me about 10 hours looking at the inside of the gearbox to get this all right.

• When you go to put the case back on make sure the shims are aligned properly. If they are not you wont be able to shift cleanly or at all.

• Don't freak out if you put the whole car back together and cant shift gears. You can pull the gearbox casing off the gearbox when it is installed in the car and have a fiddle. Not ideal but relatively easy and saves the heartache of pulling everything apart again.

Locking the diff and reassembly:

• Once out the whole centre diff just unbolts.

• I contemplated a number of options. Besides machining a whole new assembly the best option is to weld the 4 inner of the open diff to each other and their shafts. This is more than sufficient, Avoid welding the output gears (especially the rear drive one) to the housing. This might seem stronger. Unwelded it has some play. Welded it wont and may distort, you may end up having bearing failure/ binding when you put everything back together.

• Only welding the 4 inner gears mean you don't have to remove any of the bearings or risk problematic distortion of the outer housing.

• Get as much oil off as you can. Its cas metal so use Stainless Steel tig rods, or specific rods for cast metals. Only takes 10 mins to weld.

• Test the alignment of the diff splines using the input shaft of the front diff. The torsion diff splines need to align with the welded diff splines. If they are slightly misaligned when back in the car the front diff will not go back in and you will have to leave it out. I say just leave it out either way.

• Bolt it all back together and put it back in the gearbox and in the car. Follow the workshop manual for doing up bolts etc.

• Leaving the front diff out means the gearbox oil and transfer oil will be shared. This may or may not matter to you. According to the manual they take different oils but in reality these days you can use the same oil on both.

• Make sure you seal up all the interfaces of the gearbox and trannie good and proper else they will leak. The interface between the transfer case and gearbox will now be full of oil now too where as originally it is not as far as I am aware.

• Put two 38 or 40?mm Welch plugs in the holes where the driveshafts were. These press in perfectly into the seals and don't really even need gluing or further retaining.

• You will need to keep the front hubs but pull the drive shafts out of them.

• The trannie is as much of a pain to install onto the gearbox as the gearbox is to install onto the engine. Leave the Y bracket etc off. From now on the transfer case can stay on, whenever the gearbox has to come off.

Hopefully this is of use. I will try and get some pictures up so that it makes a bit more sense.

At this point you will have a car pushing 300hp through the back wheels and what is apparently a torsion LSD in the back will act as an open diff. I have had no breakages. Car will spin up 4th gear in the wet and no longer has any understeer.

ltlrkt Newbie

ltlrkt

Posted
Posted

And your rear drive shafts have survived? Last car i knew that did this had some driveshaft and also gearbox failures so im curious to know how yours is doing or if there is any evidence of any extra wear.

Are you running a near stock setup? As in cooler, exhaust, filter and boost? I only ask because you quoted 300hp, which is usually what you get when you run those mods. I have an almost stock setup in the GTiR and ive just stripped the whole car yesterday for a new motor. So now im looking at my gearbox and im thinking to myself, should i weld up the diff??? :D

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This is a huge worry for me, because my car is relatively low mileage (only 45k km when purchased) so although I plan to own the car for a long time, a mismatched odometer reading would be hugely detrimental to resale should the day come to sell the car. Thankfully this only occurred a mile or two from home so it wasn't extremely significant. Also, the OCD part of me would be extremely irked if the numbers that showed on my dash doesn't match the actual ageing of the car. Diagnosing I had been in communication with the well renown GTR shop in the USA, U.P.garage up near University Point in Washington state. After some back and forth they said it could be one of two things: 1) The speedometer sensor that goes into the transfer case is broken 2) The actual cluster has a component that went kaput. They said this is common in older Nissan gauge clusters and that would indicate a rebuild is necessary. As I tried to figure out if it was problem #1, I resolved problem #2 by sending my cluster over to Relentless Motorsports in Dallas, TX, whom is local to me and does cluster and ECU rebuilds. He is a one man operation who meticulously replaces every chip, resistor, capacitor, and electronic component on the PCB's on a wide variety of classic and modern cars. His specialty is Lexus and Toyota, but he came highly recommended by Erik of U.P.garage since he does the rebuilds for them on GTR clusters.  For those that don't know, on R32 and R33 GTR gearboxes, the speedometer sensor is mounted in the transfer case and is purely an analog mini "generator" (opposite of an alternator essentially). Based on the speed the sensor spins it generates an AC sine wave voltage up to 5V, and sends that via two wires up to the cluster which then interprets it via the speedometer dial. The signal does NOT go to the ECU first, the wiring goes to the cluster first then the ECU after (or so I'm told).  Problems/Roadblocks I first removed the part from the car on the underside of the transfer case (drain your transfer case fluid/ATF first, guess who found out that the hard way?), and noted the transfer case fluid was EXTREMELY black, most likely never changed on my car. When attempting to turn the gears it felt extremely gritty, as if shttps://imgur.com/6TQCG3xomething was binding the shaft from rotating properly. After having to reflow the solder on my AFM sensors based on another SAU guide here, I attempted to disassemble the silicone seal on the back of the sensor to see what happened inside the sensor; turns out, it basically disintegrated itself. Wonderful. Not only had the electrical components destroyed themselves, the magnetic portion on what I thought was on the shaft also chipped and was broken. Solution So solution: find a spare part right? Wrong. Nissan has long discontinued the proper sensor part number 32702-21U19, and it is no longer obtainable either through Nissan NSA or Nissan Japan. I was SOL without proper speed or mileage readings unless I figured out a way to replace this sensor. After tons of Googling and searching on SAU, I found that there IS however a sensor that looks almost exactly like the R33/260RS one: a sensor meant for the R33/R34 GTT and GTS-T with the 5 speed manual. The part number was 25010-21U00, and the body, plug, and shaft all looked exactly the same. The gear was different at the end, but knowing the sensor's gear is held on with a circlip, I figured I could just order the part and swap the gears. Cue me ordering a new part from JustJap down in Kirrawee, NSW, then waiting almost 3 weeks for shipping and customs clearing. The part finally arrives and what did I find? The freaking shaft lengths don't match. $&%* I discussed with Erik how to proceed, and figuring that I basically destroyed the sensor trying to get the shaft out of the damaged sensor from my car. we deemed it too dangerous to try and attempt to swap shafts to the correct length. I had to find a local CNC machinist to help me cut and notch down the shaft. After tons of frantic calling on a Friday afternoon, I managed to get hold of someone and he said he'd be able to do it over half a week. I sent him photos and had him take measurements to match not only the correct length and notch fitment, but also a groove to machine out to hold the retentive circlip. And the end result? *chef's kiss* Perfect. Since I didn't have pliers with me when I picked up the items, I tested the old gear and circlip on. Perfect fit. After that it was simply swapping out the plug bracket to the new sensor, mount it on the transfer case, refill with ATF/Nissan Matic Fluid D, then test out function. Thankfully with the rebuilt cluster and the new sensor, both the speedometer and odometer and now working properly!   And there you have it. About 5-6 weeks of headaches wrapped up in a 15 minute photo essay. As I was told it is rare for sensors of this generation to die so dramatically, but you never know what could go wrong with a 25+ year old car. I HOPE that no one else has to go through this problem like I did, so with my take on a solution I hope it helps others who may encounter this issue in the future. For the TL;DR: 1) Sensor breaks. 2) Find a replacement GTT/GTS-T sensor. 3) Find a CNC machinist to have you cut it down to proper specs. 4) Reinstall then pray to the JDM gods.   Hope this guide/story helps anyone else encountering this problem!
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