Pinion Depth

[jeff denton]

Surely some of you knew this was coming
Not having access to the FSM all the great tool info that Otto posted recently is gobbledy-gook to me. A search turns up no evidence of a GT diff ever being totally rebuilt at this great website. Yet.
So, where would one begin the process of choosing what shims to place under the rear bearing race?
Would I be safe to do this the old fashioned way, by trial and error, looking for full contact pattern?
Next, what is the advised method of setting pinion bearing preload?
Finally, what is the correct ring gear backlash? And would there be anything wrong with doing it the Chevy way, shims outboard of the races instead of under the bearing cone?
I appreciate any expert advice available, and promise to share part numbers, photos and installation guide of my "inner axle/housing seal" that my fellow racers will want to copy.
Thanks, and Opel On...

[baz]

jeff next time we are on line PM me and i will send you the fsm and you will need acrobat to read it
you need windows messenger and i will trancefer the file on that will not take long

[lewdawg]

Will be rebuilding my rear end in the near future as well. It howls under a load which is typical of a worn ring and pinion. I need all the info on where to get the parts and set up procedures please. Must get this done before the noise drives me nuts!!! Thanks

[baz]

i sent you a PM if you want it just follow the instructions
you may not have the pm's enabiled in the user profile so posted here to let you knowfor anyone on aol or yahoo messenger im on as bazopelgt

[GTJIM]

Originally Posted by jeff denton Surely some of you knew this was coming Thanks, and Opel On...

Jeff,
Opel uses an extremely complicated set of gauges and measurements to set up pinion depth.
However..... Check the existing pinion for shim thickness and the markings on the inner (gear) end of it. There is a two digit number there with either a "+" or "-" in front of it like: +20 or -18 or something similar. Now look at the replacement pinion and see what height variation number is written on it.
The difference between these numbers gives a good indication to how much extra (or less) thickness the new pinion shim needs to be.
"+20" means the pinion is 0.20mm above the standard position and needs 0.20mm LESS shim "-18" means the pinion is 0.18mm below the standard position and needs 0.18mm MORE shim.
So if, for instance you were replacing a "+20" pinion with a "-18" pinion you would need 0.20mm plus 0.18mm = 0.38mm MORE shim than the "+20" pinion originally had to bring the new "-18" pinion to the same level as the original "+20" pinion. This would give you a good starting point to do the "trial and error - find the full contact pattern" thing.
If you have an empty housing and have binned the existing pinion - you will need a FSM and some special gauges to find your start position. Or just put in a 0.100" shim and use that as a start point for your trial and error.

The pinion preload is set by tightening the pinion nut till the pinion shaft requires 13 inch-lbs, with new bearings or 8 inch-lbs, with used bearings to cause rotation. The crownwheel carrier is shimmed to give 0.004" to 0.008" (0.005" ideal) backlash between the crownwheel and pinion. Use feeler gauges to get the initial shim sizes each side and to get the proper prelaod add 0.002" (0.05mm) to each side for new bearings or 0.012" (0.03mm) for used bearings. The bearing cap bolts are tightened to 32.5 lb-ft

Hope that gives you a fighting chance!

[jeff denton]

Thanks, guys. I was wondering what all those numbers on the pinions were for. This sounds real simple. And away we go!

[jeff denton]

And back we are...
Haven't seen the FSM version yet, but I went out to the shop and wrote down the numbers found on the pinions, which has me confused.
The old 3.44 pinion has the following markings: 485 Z +6 +42
The new 4.22 pinion says: 224 M +12 +22
Too many plus numbers according to Jim's advice...
There were two shims under the cup, they measure .010" each that would be a total of .5mm, correct?

[GTJIM]

Originally Posted by jeff denton And back we are... The old 3.44 pinion has the following markings: 485 Z +6 +42 The new 4.22 pinion says: 224 M +12 +22 The LH number is the "Reference Number" - it gives the absolute difference between the gear tooth and ground bearing face dimension. The RH number is usually underlined and is the "Control Number" used for gauging. You need to use the LH number whichis only 0.06mm (0.0015") difference. VERY small soI would try it with the existing two shims or change one for a 0.008" shim perhaps There were two shims under the cup, they measure .010" each that would be a total of .5mm, correct?

Yep! That is dang close .....

[namba209]

Darn Jim, that Green is really hard to read against the gray bacxkground. Hurts my eyes, need sunglasses.

[GTJIM]

Originally Posted by namba209 Darn Jim, that Green is really hard to read against the gray bacxkground. Hurts my eyes, need sunglasses.

Sorry! I noticed that after the upload ... too late.

BTW: Jeff the "Control Number" is different because it takes into account the overall length of the pinion from bearing face to the gear end. Where as the "Reference Number" is an absolute position number for the gear tooth flanks. The gauging is done off the end of the pinion so that is why the "Control Number" is there too.

[jeff denton]

Thank you, Jim. You've just made this way too easy now! Fifteen ten-thousandths of an inch just doesn't sound like enough to worry about, huh? I will put both shims in and check pattern, I'm sure it will be fine!
Parts are trickling in, it should go together this weekend.
The car will be in a MAC tools show next week, will be on the track "Test and Tune Day" April 30th.
Man, this gear better be right! What an expensive little track tuning exercise this has been... But I do feel better about our later style wheel bearings!!

[Crusher]

My car had the same problem...I replaced the pinion bearing and started with the same shim thickness since I didn't change the pinion gear.
Be sure to get a new crush sleeve to set your pinion pre-load tension.
Your going to need the tool to hold the spline while you set the pinion tension,
it does require a bit of force when using a new crush sleeve...make small adjustments the recheck tension.
Once all the loaded drag mesurements and backlash meet spec, you should have a nice quiet diff.

[jeff denton]

What a piece of cake. Forget stamped numbers and the FSM. The old fashioned heavy truck way worked just fine!
The two shims totaling .020 made the pinion ride to the outside of the ring gear, according to the pattern left by running wheel bearing grease through the gears.
A .030 shim from the shim collection drawer needed a bit of trimming to fit, then in it went, leaving the others out. Pattern looked perfect. .010 off makes a big difference!
The chevy method of shimming backlash/setting carrier bearing preload seems to work vey well. Much simpler than having to pull a bearing cone off to adjust shim thickness!
To anybody who needs to overhaul their diff or change the gears, just use common sense. The Opel way will drive you crazy plus you'd have to buy special tools to do it anyway.

[GTJIM]

Originally Posted by jeff denton What a piece of cake. The chevy method of shimming backlash/setting carrier bearing preload seems to work vey well. Much simpler than having to pull a bearing cone off to adjust shim thickness! To anybody who needs to overhaul their diff or change the gears, just use common sense. The Opel way will drive you crazy plus you'd have to buy special tools to do it anyway.

Glad to see it all worked out without having to resort to the bothersome Opel way. A diff is a diff when all said and done - once the basic method and contact patterns are understood the rest is gravy!

[guyopel]

Does anyone know if the 1985 t body chevette ring & pinion gears and brgs.
will work in the opel diff. ( ratios are 3.36 & 3.62 )
thanks John L.

[mark gibson]

Hey where has DTM gone to have you heard about his race this last weekend? Has he got the new flywheel in? Glad you got the rearend together. Carrier shims have evolved somewhat. Instead of using shims on the side bearings they now have a "packet" for both sides theat allows you to stack shims inside of these "Packets" it eliminates the problem of the shims becoming hot and worn and then spitting out. You can get them from your local aftermarket, differential rebuilder. They work great and eliminate the hassle of stacking. Just for future reference.

[jeff denton]

From all the research I've done on the Opel diff, the only parts that work are from Opel or Isuzu. Period. There's lots of threads about this in the archives here. There are aftermarket gearsets and limited slip carriers, though.