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Discussion Starter · #1 ·
Been giving a lot of thought to changing the ratio in my diff and giving it an overhaul at the same time. Currently has a Dana 36 I believe as this was standard on all the 81 automatics (correct me if I am wrong) which is 2.72.

I am about to drop an LS1 and 4L60E in the car and I think that ratio will make the OD unusable. So I wouldn't mind puting in a 3.54 to be able to use the OD and also to make it over all a little more lively. I am thinking whilst I have the diff out I should get the rest of its components serviced/replaced as well.

Here's the problem thought, I live in Australia. So sending the diff to one of the people normally recommended on the forum is kind of out of the question. I have been recommended a local guy who rebuilds diffs often for hot rods/muscle cars etc. But I don't think he has done this particular diff before. Also I would need to get the parts for the rebuild shipped to him.

Do you think I should just buy one of the rebuilt diffs from one of the US vendors that has the ratio I want? (That is going to be expensive though with shipping)

This guy is apparently very good, but since he has less experience doing these then some of the US guys I guess the chances of a stuff up are increased.

Can anyone lend me some advice?
 

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Well I've offered this opinion many times so I'm sure I'll bore some out there but will go ahead anyway.

An LS motor will probably be pushing over 500hp? Me I wouldn't use a 80-82 diff in any vette, I just don't like them and they can not be built anywhere as strong as an iron diff can be.

Those diff's were designed for under 200hp to save weight and MPG (during the late 70's oil rip offs). They vary from one to another,some hold up pretty well to over 350hp others break the caps with the stock engines.

The best built 80-82 diffs are ones that Mike fits a steel cap to. Will it hold to the 500 hp maybe, Mike can add in his advice here. As far as I know Mike is the only one fitting the caps, I refuse to.

I would build a Super 10 and use it, I did one for a guy in Australia not long ago. No idea if he's near you or not but my Super 10's should handle 500hp in most applications BUT nothing is bullet proof. I've seen 12 bolts & 9" break with enough abuse.

Now the concern is shipping vs local rebuilding. Look over all my threads on the way I build them and then speak to your local guy. If he understands the process, has a surface grinder, miller, lathe and measuring tools then maybe that's the way to go.

As for buying a built stock unit, I would ask a certain fellow who posted about one on vettemod not long ago. I'm sure you'll find the link or someone will link it for you. Be very careful about what you want and how it's done.

WIth that said, I wish you good luck with your car. If I can help or answer any questions let me know.:thumbsup:
 

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Discussion Starter · #3 ·
Ok will add a few more details.

The LS1 will be remaining stock as I am not looking for ridiculous power and don't intend to race/drag the car. (the main reason for the change was the original engine was cactus when I bought the car) So the engine with the tune it has on it should be making around 320HP.

The 81 automatic has a Dana 44 right? I know with the C4s the autos had the 36 and the manuals had the 44, but I am not sure about the 80-82 C3s.

I know the guy who might work on my diff has done some Dana 44s before, but I think those are the non IRS ones found on Jeeps. Speaking to him he seems fairly confident.

What is the best source for the ring and pinion? Does anyone sell a really good rebuild kit?
 

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320 HP is a step up from the 180 / 190 HP those cars came with but a stock rebuild would be fine for cruising.

We sell the bearing kit (timken bearings) in our store http://www.vtechcorvette.com/Differentials.html

I think you shuld also be prepaired to change the center pin & the stub axles also with the hardened tips. I think just about every 80 - 82 vett we have have done the center pin has been replaced and / or needed new stub axles.

Get your self a copy of the service manual showing the rebuild procedure for your car and share it with your builder if he has not done one before. The units are not difficult to work on. The end result just has to be correct backlash and a good pattern with no leaks.

Hopefully you have a freight forwarder that you can consolidate the shipping with? Most of our off shore customers just buy a differential with the ratio they want and keep their original.

Any questions you or your builder can give us an email [email protected] . We do not have the time to get on the forums and check our PM's.

Good luck

Gary V.
 

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Discussion Starter · #5 ·
Ok adding up the costs for my options:

1. Rebuild locally:
- Gasket $8
- Bearing Kit $140
- Clutch Pack $90
- Ring and Pinion $170
- Shipping $100
- Labour $400 - $600
Total ($908 - $1108)

2. Buy rebuilt unit
- Unit $850
- Core charge $300
- Shipping $ 200
Total ($1350)

It would be a no brainer if I could get the core charge back, but that will be very difficult. Maybe I can see if I can sell my original to someone else in Australia (there is absolutely nothing wrong with it at the moment, except the ratio and with the engine change I would prefer all new components in the driveline).
 

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Assuming your local rebuilder offers a warranty on his work, and you have warranties for all the ordered parts, then stay local.

It's cheaper, and probably faster if he can get it in and get it out without a lot of fuss.
 

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If he hasn't done a corvette dana 44 before I wouldn't advise letting him do yours. I have several custom D44's in customers' cars with over 500 hp.
All 44 diffs are not alike. Cap thicknesses vary up to .200. The left side cap carries all the load and are prone to breaking. Apples to apples the 44 uses stronger internal components than the iron diff. But the aluminum case and caps, and poor machining, or lack of machining makes them inferior. My steel cap makes them a much stronger unit but I wouldn't recommend abusing them.
Mike
 
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