Gear Ratio
 

I just bought a 72 suburban and signed up to this forum...looks like there is a lot of great information here. I'm hoping someone can help me identify the rear end as well as if it's limited slip, posi, or open. I apologize for the ignorance, it's been about 20 years since I last did any major auto work. From what I have gathered I have a H072. I'm trying to confirm that as well as the gear ratio. I lifted one tire off the ground and rotated the tire 10 times getting 19.5 revolutions of the driveshaft, which i figured to be a 3.90 gear ratio. I took off the cover and couldn't find any markings except 22-2, but counted 41 splines.

I do know the front is a Dana 44 with the marking 45-11, which leads me to believe they are 4:10. Soooo, I'm a bit confused..looking for help. 4th picture is the 22-2 and last picture is of the Dana 44 up front.



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Re: Gear Ratio
 

The 45-11 on the ring gear is the number of teeth on the gears. It's a 4.10:1

The axle is an Eaton. I'm not sure of the visible cues to differentiate a HO52 from a HO72

A picture of the ring gear side of the differential case might help identify a limited slip.

Re: Gear Ratio
 

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The ring gear & pinion numbers should be stamped into the rear ring gear too. Here is a chart for them.

Rear Axle Ratios

Ratio 2.56:1 - Tooth Combination 41,16
Ratio 2.73:1 - Tooth Combination 41,15
Ratio 3.07:1 - Tooth Combination 43,14
Ratio 3.08:1 - Tooth Combination 40,13
Ratio 3.08:1 - Tooth Combination 37,12
Ratio 3.31:1 - Tooth Combination 43,13
Ratio 3.36:1 - Tooth Combination 37,11
Ratio 3.42:1 - Tooth Combination 41,12
Ratio 3.55:1 - Tooth Combination 39,11
Ratio 3.73:1 - Tooth Combination 41,11
Ratio 4.10:1 - Tooth Combination 41,10
Ratio 4.10:1 - Tooth Combination 45,11
Ratio 4.11:1 - Tooth Combination 37,9

The tooth combination numbers will be found stamped into the ring gear when you take the back cover off.

LockDoc

Re: Gear Ratio
 

Welcome to the forum!

Tell us a little about what you are working on.

Looking forward to seeing more of your project!

Re: Gear Ratio
 

Thanks for the responses. The only markings II could find on the ring and pinion in the rear is the 22-2, but counted 41 splines, couldn't see any of the other gears in there, specifically any markings without removing the third member. That's why I took the rear cover off, because I wasn't sure on the driveline test.

It's a 72 3/4 ton 4x4. Making it a nice daily driver for my wife and three daughters. Not going to be a show car but should be pretty nice when done. Removed the old 350 and putting a newer slightly built 350 for now. Looking for recommendations on my next motor swap? Thought about putting an LS3 in there. Also trying to decide between rebuilding the th350 or swapping it for a Monster 700r4. Has an NP205 getting that rebuilt. Getting the drive train back in so she can idrive while i have a donor body blasted, get the metal work done on the lower doors and painted. The. Will finish the interior, install the AC and do the body swap. Big project for me, but should be fun and will learn a lot in the process.

Any recommendations on fabricators/body work guys in the Boise area? Thanks again for the help. Will post pictures as I go.

Re: Gear Ratio
 

No worries, Suburban's are a big project for everyone.

Re: Gear Ratio
 

Cool build. That rear is a HO52. The HO72 is the dually 1 ton rear. Center sections interchange. They made 3 ratios for these rears 4.10, 4.57, and 5.14. Would stand to reason that you would have the 4.10's. If you have any issues with rear brakes, there are disc kits that are designed for them and also with a little work, 14 bolt stuff will work too.

Re: Gear Ratio
 

If you can't find the rear ratio numbers on the ring gear I'm betting someone put aftermarket gears in it. You will have to get a good light and see if you can count the teeth on the pinion gear.

LockDoc

Re: Gear Ratio
 

Welcome to the club.:welcoem: Your Suburban sounds like mine.

Go ahead and post up some before pics. If your SPID is intact post in that thread too.

I didn't even noticed that the last pic was of your Dana 44.

Re: Gear Ratio
 

Its amazing how many people think they have a H072 axle. K20s were built with H052. Saw where one guy was offering his K20 as a "factory" H0110 with only eight lugs!
The load bolt is not a primary identifier. The axle code should be clearly stamped into the carrier case.

H072s were 1-ton axles made in both SRW and DRW with bigger brake drums in either of the configurations than a CK20 H052.


My guess is that unless you are showing an optional ratio or a NoSpin on the SPID you are going to find a code RJH

Here are the powertrain chats for 72 Subs and the 72 axle codes from the parts manual (its not a complete listing though).

Re: Gear Ratio
 

Thank you everyone for all the information, much appreciated!! Thanks for the clarification on the H052 vs. H072, sounds like H052 it is. Here are some pictures from when I purchased it.
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Re: Gear Ratio
 

Nice Burb and welcome to the forum!!

Re: Gear Ratio
 

Looks solid from here.