Axle Identification

[bad neighbor]

Hi all
I have read other post trying to figure this out and still not sure. It does have ff axles. Code in glove box is HC8 which is just 3:21 gear ratio. This is in a 85 Burb 3/4 ton. I think it is either a Chevy 10 1/2 , 10 1/2 Dana or a 9 1/2 Dana going by a 83 shop manual. I doubt if they changed much. Need to get axle seals and not sure what I have. Maybe the pics will help. I see no tags on it.

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[bucket]

That's the GM/Chevy/Corporate 14 bolt, full floater with 10.5" ring gear. Not a Dana.

 

[bad neighbor]

I think I just found the clue. The Chevy 10 1/2" has a large bolt on pinion seal retainer that goes on after seal # 8 in the 1st pic. Mine has that bolt on flange. The Dana's ( 2nd pic ) are more like the Chevy 8 1/2" and the 9 1/2". Yes no?

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[bad neighbor]

That's the GM/Chevy/Corporate 14 bolt, full floater with 10.5" ring gear. Not a Dana.

Thanks for confirming that. Didn't realize I had the heavy of an axle back there.

 

[Craig 85]

Code in glove box is HC8 which is just 3:21 gear ratio. This is in a 85 Burb 3/4 ton.

I've never seen a 3.21 gear in a 3/4 ton Suburban, especially with a 454. I thought the highest gear (not numerically) was a 3.73?

Look for GT4 = 3.73 or GT5 = 4.10 on the RPO codes. G80 is a Limited slip.

 

[bucket]

I've never seen a 3.21 gear in a 3/4 ton Suburban, especially with a 454. I thought the highest gear (not numerically) was a 3.73?

Look for GT4 = 3.73 or GT5 = 4.10 on the RPO codes. G80 is a Limited slip.

I believe @HotRodPC had one with a 3.21 rear.

 

[bad neighbor]

Yup HC8 3:21 Just double checked. I don't really like it though.
It robs a lot of power from the 454. I think a 3:73 would be a lot better.

 

[Craig 85]

Yup HC8 3:21 Just double checked. I don't really like it though.
It robs a lot of power from the 454. I think a 3:73 would be a lot better.

Interesting. My '88 C20 Suburban had a 454 with 4.10's and it ran like a scalded ape!

I've had 4 other Suburbans with 454's or an 8.1L with 4.10's and they really tow better than my current '01 Suburban 2500 8.1L with 3.73's. Mileage sucks, but they are more responsive than the 3.73's. I live at the 3000 ft elevation, so I notice it more up here when towing in the hills.

 

[HotRodPC]

I believe @HotRodPC had one with a 3.21 rear.

Yes I did. My 86 C20 Big block truck was 3.21's. Not a bad ratio if you're not towing. Even with a 454 it was a slow mover towing any significant weight. But I did get 13.2 mpg not towing, highway driving at 70mph consistantly, and that's accurate with an odometer and speedometer that was dead nuts accurate according to GPS and mile markers.

 

[HotRodPC]

Interesting. My '88 C20 Suburban had a 454 with 4.10's and it ran like a scalded ape!

I've had 4 other Suburbans with 454's or an 8.1L with 4.10's and they really tow better than my current '01 Suburban 2500 8.1L with 3.73's. Mileage sucks, but they are more responsive than the 3.73's. I live at the 3000 ft elevation, so I notice it more up here when towing in the hills.

I'd agree 4.10's are about the perfect ratio, but not the perfect combination with a Th400 cuz of mpg and upper rpms freeway driving. Makes me feel like a 4.10 ratio truck with a 4L80-E that has OD and a lock up converter would be the perfect combo for our trucks. With a 4L80-E, I'd even go for 4.56s. I love that ratio. My 64 GMC had a Dana 60 with limited slip and 4.56's. Sooo very responsive and pull a car on a trailer like it wasn't even there.

 

[SquareRoot]

My nv4500 with 4:56 gears is like a wet dream. Best of both.

 

[Raider L]

@bucket, @Craig 85,

If you all know, my rear end axle housing on the pass. side has all the RPO info stamped into the top of the axle tube. I didn't know that until someone told me when I was getting ready to order the Richmond overhaul set for my rear end. They asked me what is your rear end ratio? I said I didn't know. They told me where to look and sure enough there it was. Do these big rear ends still have that on them? Does anyone think to look on the axle tube or do they try to find the numbers on the RPO sheet? If those numbers aren't there anymore, when did GM stop putting those numbers on the axle tube. If they were building a truck or a car in the factory why wouldn't they continue to put them somewhere on the axle? How would you know what was what otherwise?

 

[bucket]

The numbers are almost always there, I do believe. Half the time, I never even bother to look. Rust scale makes it difficult to see and you never know if the gears have been swapped in the past. If I really want/need to know the ratio, I pull the cover.

 

[Craig 85]

I know when I did the axle swap in my '79 I used an '82 Suburban rear and it had the numbers on the tube, but I didn't research it. I always pull the cover and look at the numbers on the ring gear.

 

[Bextreme04]

Here's a fun one though.... HC8 wasn't even an available power team for a 1985 C20 Suburban. A 3.21 Gear was only available for the C20 Suburban with a 454/TH400 and it would have had RPO GQ1(which means it would have been the standard option)

The closest thing to HC8 in the power teams list, is HC4. Which would have been 4.56 gears and only available with the 350 or diesel.

https://www.gmheritagecenter.com/do...ion-kits/Suburban/1985-Chevrolet-Suburban.pdf