New Lsd Center In R31 Bw78 Diff Housing

[XSlayer]

Hi fellas,

New to this site, but not real new to the nissan skyline. At home I've got an old R31 series 3 Ti Sedan which has god a real whiny diff. Basically, it sounds a hell of a lot whiny when I throttle on. I'm more than certain it'd have something to do with the pinion or pinion flange setup/pre-load but more than tired of if so I'm going to tackle it by installing a LSD center as well as lower 3.23:1 gearing "as I don't go much on the idea of 2600RPM @100KPH, due to quite a lot of long highway use/driving!".

Now I've found that technical information is real hard to find on these things. I know there'd be plenty that'd say 'google it' or 'search it up', but with a couple of days of searching I've almost found nothing. The information that I am after is basically how to install the diff center from the beginning of the job to the end of it. Basically, the information that I have found is as per follows:

LSD Bearing Cap Bolts: 60nm

Pinion flange nut: Torque this up like mad, but be careful. May need to be done from 200-300 ftlb

and gradually check pre-load by using an inch-pound torque wrench. Once you get

the pinion moving with this hooked up at 12-15 inch-pounds, you then have the

correct settings!

Crown gear bolts: 145nm

Diff cacrrier cover bolts: 31nm

Axle shaft retaining plate bolts: 55nm

I've been told that it's also advisable to install brand new pinion bearings along with new seal and crush washer.

Now as to pre-sets of backlash I've got no idea on how to go about it at present.

About 15 years back, I'd sucessfully rebuilt my motor, 4-speed and Banjo on an LX torana that I used to own. This was a long time ago, but am still relatively mechanical minded and reckon I could tackle the job if I know what I'm up against.

If anyone can give me some insight on what to do that would be greatly appreciated!

Cheers fellas!

XSlayer!

[XSlayer]

Forgot to add that recently I've installed brand new diff oil in a vain attempt it'd cut down the noise, but hadn't really helped the situation.

Cheers!

[XSlayer]

I started to make up a tool this arvo to hold the pinion in place while the pinion nut gets torqued up. Apparently it might take 200-300 ft/lb before the pinion pre-load starts to torque up. I'll also make another tool "basically a socket welded to 10mm thick plate steel bar", so that I can torque up the pinion nut itself.

Was also thinking of how to check the pre-load to make sure it's correct rather than using an inch-pound torque wrench"as they're hard to get and expensive". Inch pounds "from memory" is equal to Kg as in mass of force. So using a well calibrated set of fish scales should do the trick. with this hooked onto the pinion flange, the flange should start to move at 12-15 lbs providing a new crush washer is used.

Once I get some more quipment up and really start working on all this I'll let you all know how it goes!

Cheers!

Jim.

[Daleo]

Is it an auto?

If so, there is a well known issue with the OEM gearsets in the auto diffs that causes the noise. It has to do with the ratio of teeth on the ring gear to the number on the pinion.

Basically, the idea with gearsets is, you never want pairs of teeth on opposing gears in the gearset to continually meet & mesh with each other as they rotate. This is exactly what happens due to the tooth count on the R31 auto gearset. It creates a wear pattern that will become quite noisy over time. This is the noise you hear.

In the VL; the diff ratio is almost the same, but the tooth count on both gears is different, and the noise never happens.

Changing the backlash, and also the tooth wipe on the gearset does help with making diffs quieter; but if they're already noisy, a new gearset is usually the only way out.

I fitted a new gearset to my R31 diff when I changed to an LSD, and the problem was solved; never to return.

I'd speak to a diff specialist before you potentially waste a bunch of time on this; they will have done about a billion of these. Even get them to put it up on their hoist whip off the back cover and check the gear mesh. It will take about half an hour + some new oil and you'll know which way to go.

Good luck.

[XSlayer]

Hi Daleo,

Yep, it sure is an auto. The gearing is 3.889:1. and yeah, I've also got a VL sedan which does a very similar thing. You're also quite right with the info you've provided.

The idea is to put in a new LSD center I have along with a good set of 3.23 ratio gears that I have into the skyline. Thinking that'll solve my probs, and maybe even help with the fuel economy "mainly do long highway trips". I've been looking at getting a diff place to do the work, but being so far out of town doesn't help "100K's+" and only know of one place that works on diffs and doesn't have the best of reputations either. That's basically the reason that I'd like to tackle this one myself.

Cheers!

Jim.

[turboedsloth]

You're also going to need a diff spreader to spread the casing enough to allow the backlash shims to be put in and also set the bearing preload for them. If you try and put them in without the spreader you will either break the shims, or get them in but damage the bearing, and also put a lot of metal swarf in the case

[XSlayer]

You're also going to need a diff spreader to spread the casing enough to allow the backlash shims to be put in and also set the bearing preload for them. If you try and put them in without the spreader you will either break the shims, or get them in but damage the bearing, and also put a lot of metal swarf in the case

Cheers for the advice, mate. I've done a fair whack of reading and there's a good chance I'll beed a diff spreader to do the job. I've seen a few pics of them and looks like one will be easy to make. I've seen the price on these and they go for a stupid amount. Reckon I could make one myself for practically nothing.

Yesterday I finished making up a large tool that'll allow me to hold the pinion flange so that I can undo and re tighten up the pinion nut and today I've made a large 1/2" breaker bar which will allow me to do the job. Once I've got some time to spare in the yard I'll make up a diff spreader tool and then see how I go.

Cheers mate!

Jim.

[XSlayer]

Hey Fellas!

Just thought I'd give you guys/all an update on the diff situation!

A couple of weeks ago "over a weekend" I managed to remove the diff out of the R31. I'd built a pinion flange locking tool to remove the pinion nut, but it'd actually bent-up. 10mm flat bar wasn't quite strong enough to get this nut off strangely enough! So ended up making the same thing out of 1/2" bar steel. That done the job! . I used a 6ft long breaker bar that I made up and this just managed to do the job. I don't reckon that I would have done this job in-situe/under the car, that's for sure, but anyways.....

I then opened the diff housing up and spun round the pinion flange to see what ratio was actually in there (also noting that the pinion was just a little hard to turn "later found to be a rusted/siezed bearing"). Found there was a 4.11:1 gear set in it "not exactly what the tag says!/thought it was a 3.889" and was a little worried that someone may have put in a pintara setup "axles & all", but thankfully that wasn't the case. It still had the 28 spline axles in there, thank god! anyways, I undone the bearing cap bolts on either side of the hemisphere and the centre just dropped straight out so there wasn't any need for a diff spreader tool to be made up. Next thing I done was undone the 4 nuts to the axles on each side and lightly tapped on the axles with a small hammer to get them to drop out from each side. The next problem was to attempt to remove the pinion shaft and flange "was practically a pointless excercise". I had used my long bar tool and spent a couple of hours tapping from behind it with a block buster. Was a no go. I then used a ram rod on the pinion shaft and tapped the guts out of it with the block buster and that was a no go too! ;(. Mind you, I was also spraying WD40 down the guts of it "spline area" to try and free it all up, but was pointless. Got out there the next day and done the same thing, and still wasn't any good. Had a look at my shop press "6 ton job" and that wasn't quite big enough to allow the housing to fit in the frame, so no good there.... A real good point to note to anyone playing with these on a regular basis is to grease up the pinion spline well just on the off chance that you need to pull the thing apart again and also might help prevent the pinion bearings from rusting up. Would certainly make the job a lot easier.

Next thing was to check to see whether the axles fit my new LSD centre. so I stuck the axles on their edge and slid the centre over the axle spline, and felt a sigh of relief.... Thank god it was a fit!

Anyways...,

Last monday I took the new hemisphere and gears "all with brand new bearings fitted" with the diff housing into a diff specialist in the city. I'd previously asked around on the commodore/nissan forums here in tas who was good to get the work done and they told me Phil McGrath from Clutch & Transmission in Moonah was the way to go. I gave him a call yesterday and he'd just finished the job. He found that the pinion bearing was seized which wouldn't have helped with the noise once the car was getting warmed up driving down the road, and that for some reason the axle tubes were full of thick rust/scale. I'm gonna pick up the rebuilt diff later on during the week and hopefully get it in over the weekend so I'll let you know how it all goes. All up it's worked out to be a real expensive exercise as it was $50 for the rear wheel bearings, $130 for all diff bearings/flange seal/diff gasket/crush washer, $100 for 3.23 gearing, $160 for LSD center and $590 for diff to be professionally rebuilt which includes the axle bearings to be fitted. Add $20 for a couple of litres of LSD diff oil and the total comes to $1050. Seems like a lot of coin to get the diff sorted, but I'm sure it'll be worth it in the long run, and just having that peace of mind that it's not going to blow out in the back end anytime soon is probably a good thing. I've just finished studying metals at tafe and have been offered an apprenticeship in the metals trade. I've gotta do a lot of highway miles to get to where I've gotta go so I know atleast, that the diff will hold up. Next prob will be addressing the motor. She's done around 800,000K's and still going. Idles just slightly off-beat and is a little weak on performance. I have a VL rb30 that's done 80'000K's from major overhaul and also a rebuilt VLT auto trans that I'm thinking of fitting which might get me out of trouble for quite sometime but am wondering whether the whole thing will sit in top gear at 100K's an hour? Thinking that it should do but only time will tell..

Once I've got the diff fitted, I'll let you all know how it's going.

Thanks for taking the time to read and will update shortly!

Cheers!

[XSlayer]

An Update on the diff install!

Well, she's worked out quite nicely. It took a few hours to get it in this morning "raining all the way ;(", but it's done and done well! . Took it for a good run along some nice corners and up and down the highway. Reckon the speedo's out by around 20K's but it's all good and to be expected. The diff is now as quiet as anything and I can't even hear its operation over the motor and gearbox. Worked out brilliant. Also, I finally got an engine crane on friday, so once I get some time I'll pull the motor and trans out and do this changeover. Would also like to do this 2-1/2" custom exhaust once I get a chance.