Help reading rear ended gears - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**rechinca** · 01-19-2021, 05:22 PM

So like everything else on this truck, it’s challenging. Pulled the diff cover, ugly and filthy, to clean, seal and refill. Thought it try and check the rear end for gear ratio. This is how they are stamped. Teeth cut right through the stamping! By rotating it looks to be a 3.08. Any thoughts?

**Boog** · 01-19-2021, 05:40 PM

There are numbers stamped some where in there. Can you see the end of the pinion gear? Should be something like 17/43 if I remember right stamped on one of them.
Geezer will know.

**pjmoreland** · 01-19-2021, 05:40 PM

1*:43 is probably 14:43, which would be 3.07. If you want to know for sure, then you could count the teeth on the two gears.

**rechinca** · 01-19-2021, 09:11 PM

Quote:

Originally Posted by pjmoreland

1*:43 is probably 14:43, which would be 3.07. If you want to know for sure, then you could count the teeth on the two gears.

That’s about what I figured based on marking the driveshaft and rotating the tires two full turns (no posi). Came to just past 3 full turns, but not 3 1/4, so in the 3.07/3.08 range. I needed to get the cover sealed back up and filled to move it tonight so, no more looking right now. As filthy as this was, I am going to run it a couple of months and then drain and refill again.

BigBird05 · 01-20-2021, 12:38 PM

If there stock gears look at the code on the RH axle tube. Mine is a 1972. Code RHA which is a 3.07

BRL · 01-20-2021, 06:15 PM

Kind of off the subject but did they make 3:07 and 3:08 rears at the same time?

I like the teeth counting idea if necessary.

Andy4639 · 01-20-2021, 06:44 PM

Turning the wheels and watching the drive shaft is about as close as you need. It will be dang near perfect for figuring out your gears. If it only turns 3 times you know it's not a 4:11 set!

If it turns 4 times you know it's not a 3:08 set. So with that being said if you turn it 3 1/8 times then it's got to be a 3:08.

3.07 gears were installed in automatic trucks. 3.73 gears were common in three speed trucks, and 4.11's were found with granny geared four-speed trucks.

This isn't gospel seeing how my 71 has 4:11 gears and it had just a normal 3 speed in it when I bought it from the original owner. But it's the only gear sets they used back then for the common truck.

BRL · 01-20-2021, 09:01 PM

Quote:

Originally Posted by Andy4639

...3.07 gears were installed in automatic trucks...

That would explain it.

I got my rear end from a green '70 longbed with an auto column shift in the salvage yard, and the numbers on the ring gear divided up into 3:07.

I just thought it was a 3:08 for some reason all this time.

Thanks!

Andy4639 · 01-20-2021, 10:54 PM

Quote:

Originally Posted by BRL

That would explain it.

I got my rear end from a green '70 longbed with an auto column shift in the salvage yard, and the numbers on the ring gear divided up into 3:07.

I just thought it was a 3:08 for some reason all this time.

Thanks!

I want to know can you tell any difference now that you know!

**rechinca** · 01-20-2021, 11:19 PM

Quote:

Originally Posted by BigBird05

If there stock gears look at the code on the RH axle tube. Mine is a 1972. Code RHA which is a 3.07

Unfortunately this axle came out of leaf spring truck and when they installed it, they appear to have ground off the stamping. It was done pretty decent as a retrofit, but unfortunately no way to tell by that. This truck had some bad mechanic work previous to me, so it’s one fun adventure after another.

BRL · 01-21-2021, 02:12 AM

Quote:

Originally Posted by Andy4639

...

I want to know can you tell any difference now that you know!

Of course I can, my "seat-of-the-pants" gauge is telling me it's more torky overall by .01% or something.

...what'd they do, add or subtract a tooth someplace?

01-19-2021, 05:22 PM	#1
rechinca Senior Member Join Date: Jul 2018 Location: Vacaville, CA Posts: 535	Help reading rear ended gears So like everything else on this truck, it’s challenging. Pulled the diff cover, ugly and filthy, to clean, seal and refill. Thought it try and check the rear end for gear ratio. This is how they are stamped. Teeth cut right through the stamping! By rotating it looks to be a 3.08. Any thoughts? Attached Images __________________ 1971 Custom/10 - 350/3 speed, Orange/White roof

01-19-2021, 05:40 PM	#2
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,568	Re: Help reading rear ended gears There are numbers stamped some where in there. Can you see the end of the pinion gear? Should be something like 17/43 if I remember right stamped on one of them. Geezer will know. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

01-19-2021, 05:40 PM	#3
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,067	Re: Help reading rear ended gears 1:43 is probably 14:43, which would be 3.07. If you want to know for sure, then you could count the teeth on the two gears. Last edited by pjmoreland; 01-19-2021 at 06:11 PM.*

01-20-2021, 12:38 PM	#5
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: Help reading rear ended gears If there stock gears look at the code on the RH axle tube. Mine is a 1972. Code RHA which is a 3.07

01-20-2021, 06:15 PM	#6
BRL Registered User Join Date: Jun 2014 Location: Tahuya WA Posts: 633	Re: Help reading rear ended gears Kind of off the subject but did they make 3:07 and 3:08 rears at the same time? I like the teeth counting idea if necessary.

01-20-2021, 06:44 PM	#7
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Help reading rear ended gears Turning the wheels and watching the drive shaft is about as close as you need. It will be dang near perfect for figuring out your gears. If it only turns 3 times you know it's not a 4:11 set! If it turns 4 times you know it's not a 3:08 set. So with that being said if you turn it 3 1/8 times then it's got to be a 3:08. 3.07 gears were installed in automatic trucks. 3.73 gears were common in three speed trucks, and 4.11's were found with granny geared four-speed trucks. This isn't gospel seeing how my 71 has 4:11 gears and it had just a normal 3 speed in it when I bought it from the original owner. But it's the only gear sets they used back then for the common truck. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.



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