959 Gearbox Rebuild Rambling

[robster959 0]

Hey all,

Well, my 959 always developed a nasty grinding noise under hard acceleration after a run or too and I was never able to pinpoint it. There were a few areas I thought might be the cause. At first I thought it might be that the tiny c clips that hold the shafts in on either side of the box were not tight enough. The shaft were very loosely seated and had a lot of play - not in and out, but up and down for a lack of a better way to describe it. Basically they wiggled when you moved them. So I looked and say they were worn down a bit where they seat into the bearings/ball races. I figured this would probably be it.

I bought a gear set that came with all of the gears, and bevels, including new c clips. I also picked up the gearbox shafts. I just got them and test fitted the bearings/ball races on the shaft without putting them in the box. I was certain that I would be impressed how little play there would be, but the there is exactly the same amount of "slop" I looked closer, and noticed that movement isn't between the shaft and the inner ring of the bearing where it contacts the shaft - it's between the inner and out rings of the bearing. It's as thought the bearing is worn, or loosened up. I think these are the 850 bearings.

Before I put in the new parts, I'd like to know if anyone has a similar looseness in the gearbox shafts or their setup. Or even in their ballraces. Maybe it's that my bearings are shot/poor quality?

Rob

[DavidKY502 0]

Does the noise change with motor speed. Faster motor speed faster it clicks. Or is it more wheel speed related. You say happens on accel only not on decel. From my automotive experiece and TMAXX ownerships sounds like its in a differential gear set. have you limited down to the front or rear getset yet. Removing the center shaft it should just drive the rear diff only. Then can limit it down to either a front or rear gear set. Me sounds like have too much play in the diff gears if the noise changes in relation to motor speed and not wheel speed. Start spinning faster or get more torsional torque of the diff gears starts to have too much play in them. I would try to least make sure if its front or rear noise and open that one up and check it.

Looking at my runner and shelf queen eveything on them seems to be fairly tight fit with the slightest amount of play. That all relative too could be same as yours. Hard to describe how much play something has more matter of opinion. Whats normal amount for one person cool be loose for sometbody else. What I am more concern about is how much gear play it has. If i hold the center shaft in place and one wheel in place try to turn the wheel on the opposite side of the same axle I get maybe one hole of a stock wheel of play. Also roll car foward a bit before you check this. This is to lock the diffs. If you dont roll foward will have alot more play with a unloaded diff. I am not trying to check diff play trying to check gear play only. I use point on the chasis for refereence and can turn the wheel just about one hole of a stock wheel of play only. This is before diff engagement or anything how much free play there is in the gears. Looking threw the wheel hole at referecne spot on the chasis can just about turn the wheel to the next hole and see the same spot on the chasis. This is with both my runner and my shelf queen. May have to play with it to get the right feel with ball diffs and such but that is how much free play I have in my diffs. This may help you try to check yours the same way see If one has way more free play than the other. REad this a few times please lol. I had your car in front of me I could check this and tell you if it was cool or not without opening anything. I can just take one of these RCs and turn the wheels with my hands and that and know if the diffs and all that are ok just by how they feel by turning them by hand. Hope you do understand what I am trying to explain. If not ask me some questions.

[dazaa 0]

Does the noise change with motor speed. Faster motor speed faster it clicks. Or is it more wheel speed related. You say happens on accel only not on decel. From my automotive experiece and TMAXX ownerships sounds like its in a differential gear set. have you limited down to the front or rear getset yet. Removing the center shaft it should just drive the rear diff only. Then can limit it down to either a front or rear gear set. Me sounds like have too much play in the diff gears if the noise changes in relation to motor speed and not wheel speed. Start spinning faster or get more torsional torque of the diff gears starts to have too much play in them. I would try to least make sure if its front or rear noise and open that one up and check it.

Looking at my runner and shelf queen eveything on them seems to be fairly tight fit with the slightest amount of play. That all relative too could be same as yours. Hard to describe how much play something has more matter of opinion. Whats normal amount for one person cool be loose for sometbody else. What I am more concern about is how much gear play it has. If i hold the center shaft in place and one wheel in place try to turn the wheel on the opposite side of the same axle I get maybe one hole of a stock wheel of play. Also roll car foward a bit before you check this. This is to lock the diffs. If you dont roll foward will have alot more play with a unloaded diff. I am not trying to check diff play trying to check gear play only. I use point on the chasis for refereence and can turn the wheel just about one hole of a stock wheel of play only. This is before diff engagement or anything how much free play there is in the gears. Looking threw the wheel hole at referecne spot on the chasis can just about turn the wheel to the next hole and see the same spot on the chasis. This is with both my runner and my shelf queen. May have to play with it to get the right feel with ball diffs and such but that is how much free play I have in my diffs. This may help you try to check yours the same way see If one has way more free play than the other. REad this a few times please lol. I had your car in front of me I could check this and tell you if it was cool or not without opening anything. I can just take one of these RCs and turn the wheels with my hands and that and know if the diffs and all that are ok just by how they feel by turning them by hand. Hope you do understand what I am trying to explain. If not ask me some questions.

All three of my 959s/ celicas have gearbox problems. The rear gearbox sounds awfull. crunching and grinding of the gears, I fitted nip gearcasings just incase they were damaged but its still there. My latest celica has a really loud gearbox like the gears are really rough but that could be the lack of grease BUT even at full speed the wheels only turn very slowly. The bearings are VERY loose and that could be the problem so Im saving for a new gearset with new bearings and c clips. This dtove me crazy because I really wanted to get the celica going but its only sat on the shelf. The other problem I had was when the car was togeather only 1 front wheel was turning??? All the internals are like new so im absolutly lost....

Any help would be appreciated.

Otherwise there all going to be shelfers for the rest of thier life.

dazaa

[DavidKY502 0]

One front wheel only turning could just have a bad out put shaft or stripped out splines for the shaft on the gear. I would be looking at where SA 4 or SA3 goes into SG2 the bevel gear on page 9 on the manual for the 959. Make sure the spline on the gears are ok and they fit correctly. The manuals for these show the parts but still tad limited. Was looking the manual too need to make sure have the 16 or 18 tooth pinion to go with proper 40 or 41 tooth gear. The main thing going have to do take it apart clean everything good and look at it carefully. Cleaning everything off is important because the muck and grease can hide stuff. Not sure what grease to put back in these still have some stock stuff floating around but I would mnore than likely use some teflon base type of stuff. Something that will hold up to the high rpms and pressures. Teflon type of grease seems to hold up for me and not break down. Also need to check hard to get at too the motor placement and gearing engagement. ITs too tight will cause problems or incorrect gear mesh also. When get problems like this I always go back spend few mins check all the basic stuff first to be sure thats all good. Dont assume anything about something make sure its good.

I rebuilt tmaxx diffs transmission, ones on my race trucks and crawlers and just about everything else I abuse. I have good bit of experience with these things. Also look at exploded views make sure you ahve every little washer and spacer too in the proper place. Just one tiny washer in the wrong place can mess everything up. I do feel lucky that my runner has great diffs in it and of course my shelf queeen does too. Worse comes to worse if you have just one good diff you are sure thats its good you can open that up look at it for a comparison of the realtionship of the parts and feel how much play it should have. Remember tight is not good and too loose is not good. But to tell you what tooo loose or tight is not easy really more of a feel thing from messing with them. What might be helpful to open the good diff up to look at get a reference for what it all should feel and look like when its done correctly. When done should feel smooth and not gritty. Should turn the same way all the way around and not get tight or loose in spots. Like have to develope a feel for these things. Just playing around with the good one how it feels and all will give you a reference for how it should work when its right. GOing have to take time and be patient with it. Think first time I tore open my TMAXX transmission took me 4 or 5 tries to get it back together right now I can open it and be done with it matter of minutes now instead of hours.

[Splended 4]

Since 1987 I have never had this noise-problem unless some part(s) was missplaced by me. Strip down the rear gearbox COMPLETELY and take your time to rebuild it. Read and follow the instructions CAREFULLY.

Besides that I recommend you to check the following points:

1. Does the pinion gear fit the motors axle correctly?

2. 16 t pinion gear for the 41 t drive gear, 18 t pinion gear for the 40 t drive gear.

3. Don't forget any screws, linkpins or e-rings at the gearbox.

4. Never forget the vinyl tubes at the end of the rear gearbox. Page 7, Picture 11. If they're not there it will bring out all the f-words you know...:-)

Point 4 is as important than all the other ones. Go for these basics and feel free to ask.

For the Celica I have no suggestions at the moment. Simply because I've never used them. Maybe I should take them for a spin? :-/

Splended!

[dazaa 0]

Since 1987 I have never had this noise-problem unless some part(s) was missplaced by me. Strip down the rear gearbox COMPLETELY and take your time to rebuild it. Read and follow the instructions CAREFULLY.

Besides that I recommend you to check the following points:

1. Does the pinion gear fit the motors axle correctly?

2. 16 t pinion gear for the 41 t drive gear, 18 t pinion gear for the 40 t drive gear.

3. Don't forget any screws, linkpins or e-rings at the gearbox.

4. Never forget the vinyl tubes at the end of the rear gearbox. Page 7, Picture 11. If they're not there it will bring out all the f-words you know...:-)

Point 4 is as important than all the other ones. Go for these basics and feel free to ask.

For the Celica I have no suggestions at the moment. Simply because I've never used them. Maybe I should take them for a spin? :-/

Splended!

Will have a look at no4. Just to say the celica is almost identical to the 959 apart from having a 3rd diff in the rear gearbox. Not sure what it does but its there for a reason. There isnt much of a difference between the 959 and celica apart from the body mounts and that.

dazaa

[dazaa 0]

would you belive it, they wernt on the gearbox. Pretty sure its only because I changed the gearcases. How does this affect the gearbox? Dont think its the problem as the other celica has them and still sounds awfull.

dazaa

[DavidKY502 0]

would you belive it, they wernt on the gearbox. Pretty sure its only because I changed the gearcases. How does this affect the gearbox? Dont think its the problem as the other celica has them and still sounds awfull.

dazaa

Thats the stops for the rear arms. Look at them the rear arms stop against them not having them there the arms can droop down too far and cause drive shaft to interfer with the slots they fit into.

[Splended 4]

DavidKY502 is 100% right about point #4. I'll try to build a Celica gear case from all new parts during the night, just to see if it's noizier only because of the 3. diff. In mean time you can have a look at picture 46 at page 21 to see if the setup is all wrong. I honestly doubt it eleminates the problen, but it's worth a look to be inspired to try different setups. This car has in 99% of cases I've seen been set to "normal/ medium". Never wrong to play and to try something different.

I'll update after the scratch-build.

Goodnight so long!

[robster959 0]

I'll take a close look at the gears, but comparing all my gears to the NIP ones I have, I can't see much difference. Only wear I see is in the shafts, and the sloppy bearings. Anyone know where to get individual 850s? cheap?

Rob

[Splended 4]

You can try WalawalaStore at e-bay. Good prices and fast delivery. That's my experience. You'll find them among the Porsche 959 ads.

Good luck!

[robster959 0]

You can try WalawalaStore at e-bay. Good prices and fast delivery. That's my experience. You'll find them among the Porsche 959 ads.

Good luck!

I think I got my bearing set from them before. Not sure though. I'm thinking maybe get a set of 4 that aren't the bargain type. Maybe those blue rubber sealed ones. Maybe that would also help eliminate the movement of the inner ring.

Rob

[DavidKY502 0]

Check the case robster and bearings seem sloppy replace them. Say all the gears old and new dont see a differnce in them I would be eyeballing that case then. Usually start hearing grind and clicking there some sort of play inthe gears or they are damaged somehow. Since you said cant tell difference between the old and new gears they may not be damaged but look closely at them. I seen just the slightest of wearing of gears that cause all kinds of noises before in other gearsets. Check the case make sure none of the places where bearings and shaft and all ride are not worn or damaged. That when put together it stays snugged up and none of the mounting hardware of the casse itself work itself loose. Has that happen with a TMAXXX trannie. Get all together fworked good but after some runnning the case itself would work itself loose. Then I would act all funny make some bad noises. Plus clean the case really good and look for abnormal wear or cracking. Just process of looking at it all before even order anything just try to clean it all really good and see what damage there is thats totally obvious. Maybe saying things few times over and over main thing is clean and it dont look right need ot replace it.