83 gmc jimmy 4x4 6.2 diesel rear axle tube code identification

[Clark0943]

Looking to find out what my axle tube codes mean, I don't have an axle tax on the diff cover and don't have any rpo codes left anywhere, and I don't feel like pulling the cover right now. The code I found is CFJ G117 2

 

[Carcinogen]

Probably easier/more accurate to jack it up and spin the tires comparing revolutions to the driveshaft, assuming you are just after the gear ratio.

 

[diesel4me]

A GM dealer parts counterman usually is about the only person who has a listing on axle codes ,it is incorperated in their parts catalogs..
(I bought a 1946-72 Chevy parts catalog and it has the codes for those years--no help to you unfortunately)..
I tried looking online and there is not much listed as far as axle codes,just engines mostly..

 

[dyeager535]

I don't have them downloaded to this computer, but I *believe* the axle stamping codes are available in the parts manual set for each year. Pretty sure those had the possibility of changing every year, so you'd need the codes for your specific year to be the best guess at what you have. Link in my signature.

I do agree that rotating the tires may be a better method due to the possibility of them being changed throughout the year. I'm not sure how accurate that would be with differences like 3.23 vs 3.42 vs 3.73 however.

 

[Carcinogen]

I do agree that rotating the tires may be a better method due to the possibility of them being changed throughout the year. I'm not sure how accurate that would be with differences like 3.23 vs 3.42 vs 3.73 however.

Wouldn't that just be an additional 1/2 turn(if you have an open diff) of the pinion between each?

Which leads me to another point I forgot to mention:

For an open diff, jack up one tire, spin wheel 2X and count pinion/driveshaft rotations.
For locked or limited slip, jack up both tires, spin wheels 1X (both wheels will spin together) and count pinion/driveshaft rotations.

 

[dyeager535]

Well, just over a 1/4 for 3.42 to 3.73, right? 3.23 is really uncommon, but threw it out there because it's certainly a possibility. Pinion rotation doesn't change, it's tire rotation that changes open vs. limited slip or locked. Gov lock should act as an open diff if working properly.

With slop in gears and all, you'd certainly get close, and something like 3.08 and 3.73 would be easy to spot, just never tried with something as close as 3.42 to 3.73.

 

[diesel4me]

Being a diesel,I would not be surprised if it has 2:73's ,3:08's,or 3:23:s..
Diesels usually get highway gears in 1/2 ton trucks unless ordered with deeper gears for towing,especially those with a TH350 or TH400 ..some that had 700R4's have deeper gearing,my '85 Burb with a 6.2 ,1/2 ton has 3:73's factory..

Probably be best just to pull the diff cover off and read the stamping on the gears,and inspect for any damage while its open--it will hurt nothing to give it a fresh gear oil change..I should do that to my pickup--always wondered just what ratio it has,and I've had it 13 years and never changed the gear oil,I'm sure its "due",may even be "original" !....

 

[campfire]

Well, just over a 1/4 for 3.42 to 3.73, right? 3.23 is really uncommon, but threw it out there because it's certainly a possibility. Pinion rotation doesn't change, it's tire rotation that changes open vs. limited slip or locked. Gov lock should act as an open diff if working properly.

With slop in gears and all, you'd certainly get close, and something like 3.08 and 3.73 would be easy to spot, just never tried with something as close as 3.42 to 3.73.

I had no problem telling the difference between my 3.08, 3.23, and 3.73 axle ratios using this tire-spinning method. Count carefully and do it twice to make sure you counted carefully enough.

 

[Carcinogen]

Well, just over a 1/4 for 3.42 to 3.73, right? 3.23 is really uncommon, but threw it out there because it's certainly a possibility. Pinion rotation doesn't change, it's tire rotation that changes open vs. limited slip or locked. Gov lock should act as an open diff if working properly.

With slop in gears and all, you'd certainly get close, and something like 3.08 and 3.73 would be easy to spot, just never tried with something as close as 3.42 to 3.73.

Well a 1/4X2(for an open diff)=1/2 hence that part of my post... I'm a little confused on where you are getting the pinion changing directions thing though.

 

[dyeager535]

Just general slop between the ring, pinion and axle splines. Not that you should see that if you keep tension on everything, but between 3.42 and 3.73 I figured that might make it questionable.