What Swrong With My Gearbox

[ClutchBurndout-:(]

Hey guys, i know your going to say the gearbox syncros need doing but hear me out.

my 4th gear grinds SOMETIMES when shifting into 4th, maybe 1/5 times it does it on average, so it makes me think that its something else other than the syncro, because if it was the syncro wouldnt it grind every time? this is at any speed, weather i shift at 5k or 2.5k its still the same story, every now and then it grinds, i havnt experimented fully with this but i think it might do it less when its cold? not 100% though.

what do you guys reckon? i went to a mech and he said i could thin the oil down a bit (im using motul gear 300, 75 90 or 80 90 or something) any ideas? i really dont want to have to get a reco if i dont need to.

cheers

[alr33x]

try some different fluid but its fairly common issue but 1/5 gearchanges does sound like its happening a bit too often

[joeyjoejoejuniorshabadoo]

4th gear synchro always dies first.... try redline shockproof or just let it grind and forget about it

[ClutchBurndout-:(]

4th gear synchro always dies first.... try redline shockproof or just let it grind and forget about it

it had redline in it, and i dumped it and used motul, no difference realy.

the only reason i dont want to let it grind is because what if i get a reco someday? do they reco the gears aswell ? or just the syncros?

[Spurdo]

gears or synchros, they get replaced, not repaired. and neither are cheap. synchros almost always go first. gears should only go if you drive around with bad synchros and grind them all the time but rb25 gears are pretty tough. i have the same box and mine had been grinding for a while although i got used to it and avoided the grinding and when i rebuilt it the teeth on the gears were still in perfect condition

[ClutchBurndout-:(]

my observations remains valid and yet to be unconfirmed, it might not be the syncros, as it dosent grind everytime at any rpm, it dosent grind more than it does, its a sometimes thing even at higher rpm, so what else could it be? would thinning the oil down a bit help it?

[lowbro]

my observations remains valid and yet to be unconfirmed, it might not be the syncros, as it dosent grind everytime at any rpm, it dosent grind more than it does, its a sometimes thing even at higher rpm, so what else could it be? would thinning the oil down a bit help it?

Again, I am sometimes getting this in 3rd/4th gear when shifting up at lower revs and I belive it is diff/driveshaft/gearbox related as the changing of gear operation has an effect all the way to the diff before engaing the wheels through the axle shafts, so somewhere in the whole operation it is being hesitant and causing the grind as the gear is not properly engaging in time. I am no expert but this is how I see it all working together.

I am going to have a talk with a drivetrain specialist here in Brisbane and see if it is possible to re-tune the whole drivetrain operation. I replaced my diff becuase it was so clunky, whinney and chattery and felt really loose in it's operation, but I am feeling the same type issues with a CUSCO 1.5 installed, so something along the train is causing a problem which affects all the components when working together. There could be to much play at the diff housing connection to the shaft also?

I belive I have a back-lash problem as the driveline operation is too clunky and you feel the diff kind of jolt if you are not driving nice at low rev range, if I was to drive my car like a new toyota corolla, I believe the diff would blow, it can be that bad sometimes, makes driving hard as you have to put a lot of effort into making it run smooth, probably gona burn my clutch out soon also with riding it to compensate the driveline faults ; )

You had the best oil in the gbox, if it still happens with new fluid it is not fluid related. If your synchros were gone it would be very stubborn to engage the gear at any rev and it would crunch, but it is grinding, it sounds like it just about engaged but hesitated.

This is my 2 cents worth from experience.

I drove a 98 r34 coupe with 130,000 genuine km's on the clock had service history from Japan, the driveline felt like shit, the diff was awful much like mine before I changed, the whole setup was loose and felt horrid to drive, very clunky. I believe the components in these cars work very hard and need replacing at certain km usage, much like suspension. The cradle can also be at fault with these cars causing major dramas at the back-end and tramping which in effect goes all the way through the driveline. You do get used to driving these cars with a lot of foot work but they are never smooth. 4WD is a different kettle of fish altogether.

[ClutchBurndout-:(]

Again, I am sometimes getting this in 3rd/4th gear when shifting up at lower revs and I belive it is diff/driveshaft/gearbox related as the changing of gear operation has an effect all the way to the diff before engaing the wheels through the axle shafts, so somewhere in the whole operation it is being hesitant and causing the grind as the gear is not properly engaging in time. I am no expert but this is how I see it all working together.

I am going to have a talk with a drivetrain specialist here in Brisbane and see if it is possible to re-tune the whole drivetrain operation. I replaced my diff becuase it was so clunky, whinney and chattery and felt really loose in it's operation, but I am feeling the same type issues with a CUSCO 1.5 installed, so something along the train is causing a problem which affects all the components when working together. There could be to much play at the diff housing connection to the shaft also?

I belive I have a back-lash problem as the driveline operation is too clunky and you feel the diff kind of jolt if you are not driving nice at low rev range, if I was to drive my car like a new toyota corolla, I believe the diff would blow, it can be that bad sometimes, makes driving hard as you have to put a lot of effort into making it run smooth, probably gona burn my clutch out soon also with riding it to compensate the driveline faults ; )

You had the best oil in the gbox, if it still happens with new fluid it is not fluid related. If your synchros were gone it would be very stubborn to engage the gear at any rev and it would crunch, but it is grinding, it sounds like it just about engaged but hesitated.

This is my 2 cents worth from experience.

I drove a 98 r34 coupe with 130,000 genuine km's on the clock had service history from Japan, the driveline felt like shit, the diff was awful much like mine before I changed, the whole setup was loose and felt horrid to drive, very clunky. I believe the components in these cars work very hard and need replacing at certain km usage, much like suspension. The cradle can also be at fault with these cars causing major dramas at the back-end and tramping which in effect goes all the way through the driveline. You do get used to driving these cars with a lot of foot work but they are never smooth. 4WD is a different kettle of fish altogether.

good points, we did drop the rear 2 cradle nuts to get to the back diff bolts, (the cradle being the whole main frame holidng everything) and ever since we changed the diff im getting a bit of a clunk over bumps in the rear, its either the diff or drive shaft or SOMETHING, so maybe it needs to be tweaked by a mechanic

[lowbro]

good points, we did drop the rear 2 cradle nuts to get to the back diff bolts, (the cradle being the whole main frame holidng everything) and ever since we changed the diff im getting a bit of a clunk over bumps in the rear, its either the diff or drive shaft or SOMETHING, so maybe it needs to be tweaked by a mechanic

Ever thought of re-newing all cradle bushes and diff bushes?

You will need to get insert sleeves manufactured for the rear diff bushes as they are a 1 piece unit and are not sold as a replacement OEM part, but you can purchase the bushing at a pretty good price, I paid $150 for a diff mounting set, that's 4 x bushes and 2 inserts for the fronts.

I had my front bushes replaced 2 weeks ago when the CUSCO went in, but my problem still exists and was there before that, could be the rear bushes but they still looked pretty good and were refitted? Would have been nice to renew them and have seen if the problem was still there.

I would like to renew my cradle, or even purchase a new one and have new bushes in there with alloy inserts, I hear it makes such a difference to renew that whole back end set-up as over time the bushes wear out and cause all sorts of issues. Expensive I know but if you are to keep the car for a long time would be worth it in the end.

Almost every bush under my R34 GTT has been renewed and so have the tie-rod ends etc, my car is smooth suspension wise and feels like new appart from the clunky diff and driveline problem ; (

Once this problem has been resolved my car will honestly drive like new, can't wait till that day happens!

[turboedsloth]

when you put the cusco centre in lowbro did you have the whole unit reconditioned or just chuck the centre in with old bearings?

[lowbro]

when you put the cusco centre in lowbro did you have the whole unit reconditioned or just chuck the centre in with old bearings?

Bearings supplied with the unit were installed, I bought it second hand, so not sure how good those bearings were, but only about 5000km of usage.

If the bearings were pressed correctly the unit should be running correctly, it is only at the low rev range turning etc where the diff is really uncomfortable to drive and thumps and feels like it is going to lockup or blow. 3 point turns I try to really avoid.

Have you had similair experiences with LSD, seen as we are hijacking his thread Lol!