Sure grip rear end questions

[Daves69]

Some ideas for an 8-1/4".............
http://www.forabodiesonly.com/mopar/threads/8-25-8-1-4-rebuild-and-modification.383176/

 

[74Runneer]

I found a 8 3/4 Rear end from a 70 c body with 3.23 gears for $275. Is that worth the 5 hour drive? Still waiting to hear the diff casting.

 

[Cornpatch MO]

There is a guy on ebay that rebuilds all kinds of Mopar differentials. Rebuilds the sure grip with new clutches, new ring and pinion in various ratio's, new bearings, etc.
Buy them out-right with out trading one in --ready to bolt in. I bought my 742 from him a few years ago..priced very well. Only problem was it had the smaller U joint yoke (7260) and i should have gotten the 7290 yoke........................MO

 

[Bruzilla]

I found a 8 3/4 Rear end from a 70 c body with 3.23 gears for $275. Is that worth the 5 hour drive? Still waiting to hear the diff casting.

I would say it's worth it. I just had to drive 14 hours for a transmission.

Don't worry about casting numbers. Unless you're running some 1,000+HP beast on the drag strip, they don't matter.

 

[74Runneer]

Wow, that's dedication!

Okay, do you think it's worth asking about the u joint yoke size/casting?

If I wanted to swap to 3.55 gears with sure grip, is that when it's just worth it to buy the Dr diff third member? Instead of having to pay for gears, sure grip, rebuilt kit, and labor?

 

[Bruzilla]

Wow, that's dedication!

Okay, do you think it's worth asking about the u joint yoke size/casting?

If I wanted to swap to 3.55 gears with sure grip, is that when it's just worth it to buy the Dr diff third member? Instead of having to pay for gears, sure grip, rebuilt kit, and labor?

Yep, definitely ask! I didn't have to because my drivetrain came out of a 73 Town and Country and I had the driveshaft cut down for use in the Roadrunner.

As for the center, it's all about the money. You can wait for a used 3.55 SG to come up for sale, which is the cheapest route but there's a risk the clutches will be worn, or you can pay more and buy a rebuilt unit. Either way is going to be cheaper than buying and changing one.

Also, I would advise going 3.23 vice 3.55. The difference in acceleration is minimal, but the difference in fuel mileage is significant. If you do much highway driving, I would go 3.23.

 

[74Runneer]

Yeah I might just stick with the 3.23s, 500 ft lbs of torque and 450 hp should provide enough acceleration I would think.

Whats a ball park estimation of what it would cost for a shop to install a Eaton true Trac into the open 8.75 differential with 3.23 gears? How about with a rebuild kit? Am I looking at around $1000?



Edit: he just got back to me saying that it's a 489 case with 2.76 gears.

 

[Bruzilla]

Well, you're looking at $400 or so for the unit, another $300 for the gears, and anywhere from $300 to $700 to get the work done, and that's assuming you take the unit off and deliver it to the shop. That's why I've always found it cheaper to just buy a known good unit with the right gears and be done with it.

Plus swapping centers is very easy to do in the driveway. Just jack up the rear, take off the wheels, pull the drums off, unbolt the axles and pull them out a bit, then unbolt the center and let it fall out. Put a new gasket and some sealant on, put the new center on, bolt everything back up, refill the lube and add some friction reducer, and get the wheels back on and you're ready to go.

 

[74Runneer]

Can you really find a 8.75 limited slip with 3.23-3.55 gears for under $1000?

 

[YY1]

I've bought two 3.23's and one 2.94 SG carriers for under $250 in the past 4 years.

The 2.94 was in a 67 Coronet 500 4 door 361 trailer package car and looks brand new.
It was the cheapest at $125!!

 

[74Runneer]

Wow, that's a good deal! Where did you find them? EBay? Craigslist? Swap meets?

 

[Bruzilla]

Craigslist is usually the best spot. I just missed out on one from a 70 Polara that was at a U-Pull It place in Jacksonville. It was a 3.23 Sure Grip unit that i could have got for $75 when they had a sale going, but I didn't have the tools to pull it. By the time I got back with the tools, it was gone.

 

[YY1]

One of mine came from the Don Garlits swap meet (the worst one that is kind of stiff), one came from craigslist, and believe it or not the other from ebay, and I was only 45 min from the seller's house (that was the super clean 2.94 742 case).

 

[YY1]

...and I've also picked up two non-SG complete 8 3/4 axles (including the center) for $100 each (both E body) during the same time frame and even passed on picking one up for free.

I do regret that one as time passes.

 

[74Runneer]

What's the draw to the e bodies over the c bodies?

 

[Cranky]

What's the draw to the e bodies over the c bodies?

They are somewhat plentiful. Many including me usually stuck a B body rear under them for more tire clearance. It's an easy swap with just offset rear hangers since E-body springs are splayed out at the rear hangers.....

 

[Cornpatch MO]

Can you really find a 8.75 limited slip with 3.23-3.55 gears for under $1000?

Yes you can . the complete rebuilt 742 Sure-grip differential with a new ring and pinion, cost me under $700. You have to do the searching , but they are out there. Did you not do as I suggested and check out ebay? .......................MO

 

[74Runneer]

I've been looking on ebay but the best I could find was $900

 

[MoparLeo]

Here are a few very useful inks that will help educate everyone on Mopar differentials :
https://www.forebodiesonly.com/foru...ear_id_jpg_pagespeed_ic_mia0pwdtbi-jpg.16484/
http://www.waywardgarage.com/tech/rearaxlemopar.html
http://www.hotrod.com/articles/scroungers-guide-buy-a-mopar-83-4-centersection/

 

[YY1]

I believe ALL E body cars came with an 8 3/4 axle.

The base models usually came with 2.73 open gears, but they were in the desirable "489" case.

They are some of, if not the cheapest housings you can find.