stevengerard

So after all these decades of having a car that seemed to rev pretty high on the expressway and seemed a little quick off the line I along with a mechanic finally turned the driveshaft to check the gear ratio. I am 99.9% sure (looking for photos I took of it) than my rear-end has an axle tube stamp of SX (3.42). But after turning the driveshaft we were at almost 4 rotations per one wheel rotation — thus I suspect the carrier has 3.91s in it.

We plan on taking the cover off to inspect the gears. Two questions.

1) Does anyone know if there are unique markings on the original gears? I suspect at some point they were changed but it would be nice to know what to look for.

2) Is there any special gasket I need when I close it back up?

Thanks

jensenracing77

There will be date codes on the gears and also be GM part numbers. The teeth count will be on them and you can divide them to get the ratio. When you did the drive shaft turn test, did both wheels turn the same amount? If not, it will throw off your number.

I would use the correct 70 O type gasket. It will have hooks made to help divert oil into the tubes. The ones all the repop places have are not correct. Someone is making them but I can't find them now. I will look again when I get home from work.

stevengerard

Thanks Eric. Yes, both wheels turned the same amount - maybe off an inch. We marked both tires and the driveshaft and double checked. At this point I'll most likely leave those gears in unless inspection determines they need to be replaced, then I'll put the correct gears to match the code.

Thanks, please let me know about the coer when you find it. I'll search as well now that I know what I am looking for.

joesw31

Your W27 should have the assembly date code stamped to left side, next to he cover. Also, the posi unit will have a Julian date code on the right side. Here is the correct gasket
https://www.ebay.com/itm/8-5-Oldsmob...ZZ76gI&vxp=mtr.

classicmuscle442

Always learning, did not know there was a different gasket.

stevengerard

Thanks, ordered one.

jensenracing77

Most people don't worry about it and don't seam to have a problem. You don't need to if you have the 68 style sealed bearings. The 70 bearings were not sealed and the extra oil slung in the axle tubes got more oil to the bearings. With a W-27 I would not risk it and use the correct one.

I did not know any of this till I learned it here on ClassicOldsmobile from people like joesw31

1969w3155

Here's one: https://www.oldsobsolete.com/product...et-nos-402783/