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Tahoe Axle in Caprice Wagon

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5.2K views 25 replies 7 participants last post by  Caddylack  
#1 ·
I am looking to do the 3.73 gear swap in my 95 wagon with the LT1 and 2.56 gears.
I've been told numerous times that 3.42 is the more functional upgrade, but i barely take this thing on the highway and I just want to suprise some mustangs at a couple lights with sticky tires and a beefy driveshaft.

All that being said, I am learning that i have to upgrade my carrier when i do my gear swap. This is turning into a much more expensive upgrade compared to my experience with ford 8.8's.

Can I use the axle out of a tahoe or escalade? I hear that some of them have 3.73 gears in them, but they may be the 8.6 instead of the 8.5.... but can that be a viable alternative?
Id really like to save some money on buying the carrier and possibly the gear used if they are in good shape, so please provide any input on other used cars that i could piece the parts off of. thanks!
 
#2 · (Edited)
Your title is misleading.
Yes the 8.6 gear set will interchange. ( It's the same)
The 30 spline limited slip will if you use the bearings sold to put an Eaton in an 8.5.
The 8.5 uses a smaller side bearing than the 8.6

Aftermarket 30 spline diffs like Eaton have the larger inner dia. like the 8.6
The "special" bearing is basically 8.6 inner spec , 8.5 outer spec..

That said it will likely be the " cuckoo clock" governor lock which are more suited to a truck stuck in the mud. They also like to toss parts, destroying ring and pinions.
They are awful.

If you want a preview of 3.73 on the highway, drive it in 3rd.
3.73 in 4th is near identical to 2.56 in 3rd
 
#3 ·
The axle width needs to be about the same as the stock one. Another issue you may run into is the mounting points on the donor axles. If that is an issue, it will cost more to adapt the Tahoe axle than a new carrier.

If you are looking to surprise someone, you should have a posi. The posi is going to be the biggest single expense. I put an Eaton Truetrac in mine, when I rebuilt it. The total cost was about $1000. I put Moser axles in it, all new bearings, races, and seals. I had to buy a couple of tools, but had a caliper, dial gauge, and torque wrenches. I installed 3.42 gears, and am happy with them.

The one disconcerting part of building a rear is the pinion shim. If you use a 0.038-0.042 shim you will be in the range that the rear needs. I used a 0.038 in mine, and the mesh pattern is excellent. The 0.042 shim will put the pinion a little deeper into the ring, and make it a little stronger, but will still have an excellent mesh pattern. You can install the pinion bearing by freezing the pinion in the refrigerator, and heating the bearing in a pan on the stove. Put the shim on the pinion, and drop the bearing on the shaft. It will make a loud clunk, and it will be installed. Put some oil on it to keep it from rusting, because the pinion will have a lot of condensation on it.

You can use a bearing installer borrowed from Autozone, and use a hammer to install the bearings on the carrier. You might need some extra preload shims for the carrier, because the kit does not come with enough variations in thickness. Get the carrier snug in the housing with shims at the correct lash. Lash is between 0.005, and 0.009 on the dial gauge. You can tap it right and left with a dead blow hammer to seat the shims. When setting the preload, you must add 0.006 on each side of the carrier bearings. (You can remove a 0.012, and replace it with a 0.018 on each side to achieve this, or other similar dimensional swap). Place all of the thick and thin shims in the rear, except for one thick one, then insert the thick one at its end...push it in as far as it will go, and use the bearing cap and a dead blow hammer to gently insert it into the stack. Use the new shims, because the old ones are cast iron, and can crack.

I used piece of steel tubing to remove the bearing races, and installed them with the bearing/seat/seal installation tool from Autozone. It took me more time to clean and prep the housing than to assemble the rear. Follow the FSM when doing the install. There is no magic in building a good rear, just be exacting in your measurements. If you need any info from me, feel free to contact me about it.
 
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#4 ·
ojb226 said:
I am looking to do the 3.73 gear swap in my 95 wagon with the LT1 and 2.56 gears.
I've been told numerous times that 3.42 is the more functional upgrade, but i barely take this thing on the highway and I just want to suprise some mustangs at a couple lights with sticky tires and a beefy driveshaft.

All that being said, I am learning that i have to upgrade my carrier when i do my gear swap. This is turning into a much more expensive upgrade compared to my experience with ford 8.8's.

Can I use the axle out of a tahoe or escalade? I hear that some of them have 3.73 gears in them, but they may be the 8.6 instead of the 8.5.... but can that be a viable alternative?
Id really like to save some money on buying the carrier and possibly the gear used if they are in good shape, so please provide any input on other used cars that i could piece the parts off of. thanks!
Click to expand...
What you want to focus on is the GMT360 platform (Trailblazer, Envoy, etc.).

Do you have self-service yards near you? You should be able to pull a complete rear axle, disc-to-disc, for say $100, give or take. Only takes a few minutes to remove with a sawzall.

The Trailblazer and Envoy came with 8.6" rears and locking differentials. Available gear ratios were 3.42, 3.73, and 4.10.

Just walk around the yard and check the stickers in the glove boxes until you find something with G80 and 3.73 gears.

I would also recommend grabbing the rear sway bar while you are at it... 😁
 
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#6 ·
#9 ·
Please understand my intentions, I am grateful for all feedback. I get to learn from others knowledge and experience. It's just nice to hear options and budget minded alternatives that I can consider in my build.

So am I able to put the 3 series carrier and 3.73 ring and pinion from an 8.6 into a 8.5 inch ?

I am not interested in the 8.6 axles or housing
 
O
#11 ·
If you are junk-yarding, a truck rear-end with drum brakes is an 8.5 and a disc brake axle is an 8.6, short wheelbase Trailblazers use a small differential, but the long wheelbase EXT have an 8.6. If the rear doors on the Trailblazer are part of the rear wheel opening, it is a short wheelbase and if the doors are ahead of the wheel opening, it is a long wheelbase. I used a gov-loc in my wagon and it works well for my mild combination. I don't know if the truck pinion gear is ABS compatible or I would probably have grabbed a set of 3.73 gears also.
 
#15 ·
From memory, I want to say the short/long wheelbase part is usually true, but not always.

The long wheelbase EXT used the 8.6, but I think the short wheelbase with the V8 still used the 8.6 as well. That's why I didn't say anything about the doors, and instead referred to the SPID sticker.

The doors are still definitely worth mentioning, though.
 
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#12 ·
Old Coot,
You will find the 8.5 and 8.6 share the exact same gear set fitment wise.
The diff " they" call an 8.5 ran from 1971 to about 98ish
The 8.6 98ish up.
8.5″ used bearing LM501349 and race LM501314. The inner dia. 1.625″ , outer dia. 2.890″, same as 7.5-7.6 diff.

8.6″ used LM603049 LM603012. Inner 1.780″, outer 3.060″ , same as the 8.875 12 bolt .

Although the 8.6 never ( as far as I know) had a reluctor on the pinion, the factory gear set was machibed for it. One of my diffs has a GM gear set from a late application .
 
#14 ·
You will need a reluctor that matches the gear ratio you use. The one from your 2.56 gearset will not work with the 3.23, or 3.42.
 
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