Cunching Syncros At High Rpm

[PJ.]

Ah who told you that!! I think the "clips: you may be refering to are the syncro Paws and there is stuff all you can do with 4th gear without stripping the box to nothing as 4th gear IS the input shaft.

2 different places that have put them back in without stripping it!

[Risking]

do yourself a faour and grab a copy of the workshop manual. Even for an RB20 or CAa8 etc, have a look at the exploded view of almost any nissan transmission and explain which clips they are putting back in each time??

Im curious cause I have been doing these boxes for years and not one of the syncro's is servicable or even accessable without removing the extension housing and bellhousing then pulling it down.

I know anyone who knows anything about transmissions will agree with me as well.

[tom23q]

today i purchased "royal purple max gear" gear oil for my car today, apparently its better than the redline products... im going to put this in sometime this week if i get a chance. i will update the results once i have put the oil into the gear box

well i put the oil in today... first thing i notice when i drained the oil from the gearbox was that it was a bit old n dirty, the drain plug had a few shavings on it but nothing to worry about. it took 3 litres of oil to fill up and after i took it for a test run the 1st thing that i notice was the smoothness of changing gears even at hig revs... so i think ive fix my problem and i hope this helps someone else. also keep in mind my car has only done 65,000kms

[NYTSKY]

well i put the oil in today... first thing i notice when i drained the oil from the gearbox was that it was a bit old n dirty, the drain plug had a few shavings on it but nothing to worry about. it took 3 litres of oil to fill up and after i took it for a test run the 1st thing that i notice was the smoothness of changing gears even at hig revs... so i think ive fix my problem and i hope this helps someone else. also keep in mind my car has only done 65,000kms

How much was the Max gear oil/how many litres?

What weight?

[furryfrog]

2 different places that have put them back in without stripping it!

there is no chance in hell they can without stripping it, and without access to the right tools you arent gonna get very far not to mention all the clearances you need to take into consideration. get em wrong and at best you will have a clunky ass box... or at worst a box with stripped gears.

[Risking]

Damn finally someone agrees!

Clearances on a conventional nissan box arent as critical as a transaxle but still baulk ring air gaps etc do need to be right.

[Kinks]

My theory is that the r33 box and gearset is very strong. Like everything else though (and the way the skylines get driven), the synchros wear out.

My theory is that the synchros are just inadequate. My car was in near mint condition when I bought it and only 34,000km. With the original oil in it, 4th and 5th would grind. With Motul full synth in, 5th still grinds. They're just weak synchros!! Wear has nothing to do with it, by all accounts my car was cherished when it lived in Japan and it still has the problem.

[Risking]

They are not weak syncros! The double syncro in the Nissan box is amongst the best there is!

Wear has EVERYTHING to do with the result you feel. A weak syncro will break not cause crunching.

Do any of you know exactly what part of a syncro actually wears for it to begin crunching???

Or even how a syncro in fact works?? A better understanding of the component would help you come to terms with what can wear.

For instance you can baby a car around for 50000Km's BUT rest your hand on the gear stick all the time and wear out a selector ring. INSTANT crunching! and you have not even flogged the vehicle yet! I little pressure on the stick equates to a load on the selector fork and ring hence premature wear.

Dont be blaming the syncro's inside a gearbox you dont fully understand

If you have ever had a box apart thats broken a baulk ring you will know how it was to select gears, next to impossible infact.

[tom23q]

How much was the Max gear oil/how many litres?

What weight?

75 - 90w full synthetic and i used 3 litres... and yes the oil does look purple (no joke)

[PJ.]

do yourself a faour and grab a copy of the workshop manual. Even for an RB20 or CAa8 etc, have a look at the exploded view of almost any nissan transmission and explain which clips they are putting back in each time??

Im curious cause I have been doing these boxes for years and not one of the syncro's is servicable or even accessable without removing the extension housing and bellhousing then pulling it down.

I know anyone who knows anything about transmissions will agree with me as well.

I apologise I probably wasn't clear enough with what I was getting at.

Of course you'd have to pull the extension and bellhousing off! What I mean was stripping one of the shafts?

Edited April 10, 2007 by PJ.

[Hardman69]

Hey, I'm currently smack-bang in the middle of a 'box rooting . . . . (Oh how I wish it was as good as that sounds)

SAU Vic thread on My rooted Gearbox

It gets dropped off for a strip today, I'll be updating my Vic thread on what the damage is, literally and financially.

[furryfrog]

I apologise I probably wasn't clear enough with what I was getting at.

Of course you'd have to pull the extension and bellhousing off! What I mean was stripping one of the shafts?

yeh you have to strip the shafts so you can seperate them from one another, and remove them from the sandwich plate, thats how i had to do it with my MX7 im guessing the r33 box is identical.

[Risking]

Yes your right, to access anything syncro related 1st to 4th you have to separate the shafts from the syncros. Some boxes are designed to be "modualar" such as the PAR (evil box) these boxes you can remove the gears via circlips from the front of the box and there is no need to strip from the sandwich plate. However there is no OEM nissan boxes like this.

Perhaps yours is not a factory gear set if thats the case??

[Trex101]

75 - 90w full synthetic and i used 3 litres... and yes the oil does look purple (no joke)

Yes, RP maxgear 75w90 is purple in colour. According to the new SAE gear spec, the viscosity 21cSt @ 100'c should be rename as 75w110, RP 75w90 is thick.

[PJ.]

Yes your right, to access anything syncro related 1st to 4th you have to separate the shafts from the syncros. Some boxes are designed to be "modualar" such as the PAR (evil box) these boxes you can remove the gears via circlips from the front of the box and there is no need to strip from the sandwich plate. However there is no OEM nissan boxes like this.

Perhaps yours is not a factory gear set if thats the case??

R34 Gtt box with OS Giken Cross mission gearset 1st, 2nd, 3rd. They still use standard syncros though.

Should be able to get these clips in by pulling back the syncro hub, and not have to strip the box excluding bellousing etc...

Edited April 11, 2007 by PJ.

[Risking]

There is your answer. You cant get the syncro paws back in without taking the hub right off because there are offset springs inside the assembly that need to be located properly.

I think you will find the gear set your using is a modular design and they are pulling the front gear off the lay shaft, removing the input shaft (4th gear) and pulling the selector hub almost all the way off and putting the paws back in.

However there is something seriously wrong if you keep throwing them out. the only way for that to happen is if the hub is moving to far and allowing them to come free.

[Hardman69]

Bad news for my rebuild -

SAU Vic thread on My rooted Gearbox