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12/13/17 11:19am - Original Message: 'Where's a good differential rebuild shop near Harrisburg PA'
vince vette
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Vette(s):
1980 L82 White with doeskin interior

Joined: 1/5/2016
Posts: 71
Now that after two years' work the vette is legally back on the road I can start tackling the fun stuff - that is, getting the performance of this '80 to match it's looks. So, out with 3.08's and in with 3.55's (along with an overdrive tranny). So does anyone know a good shop for this kind of work within an hour's drive of Harrisburg, PA (or within walking distance of an airport within a hundred miles of PA, it would be a good excuse to toss the unit in a plane and fly it there). 

Also, any good tricks to getting the differential out would be appreciated. One item specifically, reading the shop manual it stated to use a C-clamp to release the tension on the spring before pulling the bolts. But it didn't show exactly where to clamp it on. 

Lastly, ask for opinions on rubber vs poly to replace the bushings that will come off when I I pull the unit. 


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12/13/17 11:45am - Reply: 'Re: Where's a good differential rebuild shop near Harrisburg PA'
manchestershark Lifetime Member
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Equinunk, PA - USA

Vette(s):
1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.

Joined: 10/31/2007
Posts: 1960
The "BEST" place to get the re-build done is indeed in Penna. Your half way across the state now. Go the distance to BAIRS in Linesville, Pa and get unequal service to anyone. They will re-build yours or trade you for the 3:56 you want. Drive one out, bring one back. No better provider this side of the Mississippi! As for the spring tension and the C-clamp. Attach the clamp, and small piece of wood or metal to the spring near the bolt, put the jack next to the clamp and jack up the spring till bolt is loose. Then remove the bolt. "SLOWLY" let the jack down and release the spring tension. Hydraulic jack works best. I have done it many times. Sorry I can't show a picture, i'm not that savvy with this thing. Maybe someone else will illustrate it.

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12/14/17 12:05am - Reply: 'Re: Where's a good differential rebuild shop near Harrisburg PA'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 487
Place the jack between the bolt and the C-clamp.  I always place a piece of compliant material between the jack and whatever it's lifting to minimize slipping like it would if were metal-to-metal.

Also don't be surprised if it appears that the spring isn't compressing as you start to raise the jack as the spring is trying to lift the car which is the reason you place the jack as close to the end of the spring as possible to maximize the amount of leverage.

Be careful as there is several hundred pounds of stored energy for each inch of compression.

If you plan to remove the spring from the diff housing, be careful as the ears are prone to breaking.  I used Kroil, heat, and an impact wrench on the ones I did.

I used the poly bushings on both sway bar brackets and end links when I auto-crossed.  Didn't use them on the A-arms or strut rods as they both squeak (this was before they had lubricated ones) and ride a little harsher.  Since this was my daily driver, didn't need that even tho might have benefited my times.


|UPDATED|12/13/2017 9:05:08 PM (AZT)|/UPDATED|


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1973 L-82 4 spd

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12/14/17 9:15am - Reply: 'Re: Where's a good differential rebuild shop near Harrisburg PA'
gtr1999
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CHESHIRE, CT - USA

Vette(s):
1969 350 4 spd drop top 1972 350 auto coupe

Joined: 5/2/2016
Posts: 61
Bairs will do a nice job on those 80-82 diff's. If you are just going to drive the car that is all you need.
If you plan on building more power and pushing the car I would not use that diff. I have converted a lot over to the iron diff's and while the initial cost is more the unit is a lot stronger.
The 80-82 Dana's were used to lighten up the car for MPG requirements, it saved 30 lbs but was a much weaker design. There are issues with the clutch retainers in the posi, the bearing caps are aluminum, and the pinion design is the throw back to the 63-64 Dana's only smaller. The earlier ones, 63-4's, broke in half with some abuse, same for those posi's.
 
Nice idea flying in someplace, I had a guy bring me a 72 diff like that once. I had to drive to the airport and since it was a small one they let me drive up to the plane to get the guy and diff.


|UPDATED|12/14/2017 6:15:03 AM (AZT)|/UPDATED|


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12/14/17 9:42am - Reply: 'Re: Where's a good differential rebuild shop near Harrisburg PA'
vince vette
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Vette(s):
1980 L82 White with doeskin interior

Joined: 1/5/2016
Posts: 71
Guys, 

Thank-you all for the advice. It is much appreciated. 

I did call Bairs. I knew I was in trouble when I saw on the website "Rebuilds, 63-79 - $649, 80-82 - call". Wow, I thought, my 80 must be special! I had an excellent discussion with them on the issues of the Dana 44. 

On the issue then of putting in something different, or not, my plan for the engine is to keep the L82 for a year or two with the only mod being a set of Tri-Y headers. Thus the HP increase would be whatever that will do including the fact that it will be true dual exhaust with hi flow cats. Given the 230 HP initial rating that may take it to 250 or so (more?). The Tri-Y's will though help to pull up the torque at lower RPM. Coupling that with going to 3.54 gears from the current 3.07 and with the retuned Q-jet which has made a noticeable difference on the low end, there will be more stress to the differential when getting started. Eventually I expect to swap in a 383 stroker with gross of around 400 hp which probably nets 300-320. So would that drive me towards a different differential? If so, what does the differential swap require - specifically, any change in mount points or drive shaft length? Also will it bolt straight onto the integrated cover/cross member in the 80 or will I have to replace that with an earlier year cross member?

Thanks, 


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12/14/17 1:48pm - Reply: 'Re: Where's a good differential rebuild shop near Harrisburg PA'
gtr1999
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CHESHIRE, CT - USA

Vette(s):
1969 350 4 spd drop top 1972 350 auto coupe

Joined: 5/2/2016
Posts: 61
well what breaks the 63-82 vette IRS parts are
  1. Power
  2. shock loading
  3. traction
  4. and your right foot.

If you have an automatic trans, street tires and don't plan on hard abusive driving- like drag racing and constant hard launches you should be ok with the stock DANA. Would I use one, no way but plenty do. Would I modify one for more power, no.

The iron units are proven, while they also had weak areas over the years, a custom built one will hold up to 1000hp if built using Tom's 12 bolt conversion parts. Of course as the level of build goes up so does the cost.
 
If I had an 80-82 I would look for a nice 73-79 iron diff with the brackets, 1/2 shafts, strut rods, and TA axle flanges. Build the diff to application- power level, use solid spicer joints, and it will be done. The iron diff will bolt to the 80 cover but you may need to replace the driveshaft or machine it. Plenty have done this conversion with very positive results.
 
So it really depends on your application, go with what you think will be the final power level, and your honest usage. If you want to talk about how these are built let me know I can go over it with you. If you have the desire I can teach you how to build them.


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12/14/17 11:33pm - Reply: 'Re: Where's a good differential rebuild shop near Harrisburg PA'
vince vette
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Vette(s):
1980 L82 White with doeskin interior

Joined: 1/5/2016
Posts: 71
gtr thanks for the info. I probably won't abuse the car like I did when I first bought it. I was 21 then, now I'm 59. I'm leaning toward sticking with the existing unit as long as it can reasonably hold up to 400 hp (gross) transferred through an automatic. If it can, then it's the simpler solution. The unit lasted through 90,000 miles of my youth from age 21 to 44. Most of that 90,000 came between age 21 to 31 at which point kid number two forced me into an Olds Delta 88 as a daily driver. But if someone offers a complete conversion kit with an already built unit I might head that way. I can get heaving into basic bolt turning, but I'm shying away from complex skilled builds since at this age I'm putting a premium on maxing driving time. 

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12/15/17 1:15pm - Reply: 'Re: Where's a good differential rebuild shop near Harrisburg PA'
gtr1999
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CHESHIRE, CT - USA

Vette(s):
1969 350 4 spd drop top 1972 350 auto coupe

Joined: 5/2/2016
Posts: 61
For your use I would go to Bair's and get it rebuilt. I personally don't care for those diff's but they will work as you know. You have a year up on me so I know the feeling!
 
Times are in transition now with these cars, I lot of the old timers who worked on them an supplied parts are retiring or dead now. It will be interesting to see where it ends up in a few years.


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