Rear-end swap - 70 to 73

[redo1973]

I have a base model 73 Barracuda that I am upgrading to a Cuda level.  The original car has a 8 3/4 axle with 2.76 gearing.  I have access to a 1970 8 3/4 axle with 3,23 gearing.   We calculated motor set-ups for other ratios and picked the 3.23 for decent highway and quick starts.  I need to make measurements but thought that I would ask opinion on this swap; will it fit and function?

[Katfish]

If it's from another e-body, it's a drop in, will fit perfectly.  70-74 all have the same dimensions.

[Moparal]

Your emergency brake lines are dif from 70 to 73. Just install the 323 chunk . It will take a couple of hours and be a lot less envolved.  If wanting the 70, keep your backing plates on that is with your car now

[Chryco Psycho]

if you are going to pull the axles to swap the gears it is easier to swap the backing plates at that point , also a 70 E body diff is the same dimensions as the 73 , if the diff is from anything else it is not .

[redo1973]

Thanks everyone.  The rear end is from a 70 Chally,is a sure grip and looks good.  I thought of just pulling the center but figured keeping the rear-end complete would be better. The guy won't break it up so I have to buy all or nothing. I'm still learning the terms so what is the problem with the e-brake lines and backing plates? I should replace the 70 with the 73 if keeping the full rear-end?

When you say install the chunk is that the entire assembly with casing or just the gear assembly?

[anlauto]

The complete rear end as an assembly will bolt right in. As mentioned, you will have to keep your 73 E Brake cables but the will install in the 70 rear end with no issues.

You'll need to check the driveshaft U joint yoke width, there are two sizes "big" and "small" if they are not the same you will need a new rear U Joint that will adapt to the two different sizes. (any local parts store can get it)

[Chryco Psycho]

They used a different E brake system in 70 so you can just swap the cables or the backing plates if the brakes are the same size , the cables are easy to swap out .
Chunk is the center cast gearset , I call it the carrier or third member .
The U joint is the other variable as mentioned .

[anlauto]

If you want to swap the backing plates, you're getting into pulling axles, replacing gaskets etc....I get the impression that he doesn't want to "service" his rear end.

[Chryco Psycho]

Exactly 

[redo1973]

Thanks.  I get what you're talking about.  I'm doing a full restoration but haven't decided how far to tear down the rear-end.  The motor is done and transmission is yet to be rebuilt.  He wants $700 for the rear-end and I can pick it up.  I don't know the mileage but expect it to be under 60k. Does it sound like a good price or should I simply look for a chunk?  I've seen chunks at car shows but I'll probably have to have it shipped.

As a side note, do you have an idea what an 833 is worth? Is it difficult to convert from an automatic set-up?

[anlauto]

Seriously .... $700 ??

I have a complete rear end out of a 1970 Cuda, e brake cables and all, listed on KiJiJi for $150 and nobody wants it.... http://toronto.kijiji.ca/c-cars-vehicles-auto-parts-tires-other-parts-accessories-1970-74-Cuda-Challenger-Rear-Axle-Mopar-W0QQAdIdZ526476382

Having a 3:23 sure grip doesn't add THAT much value....I would expect to pay $300-$400 tops for a used rear assembly unless he has bills to prove that it's 100% restored brand new with all new bearings and seals etc....

E Body 8 3/4 are a dime a dozen..........$700 is nuts 

Spend your $700 on a brand new center section

I also have a 4 spd tranny listed for $450

[Katfish]

Too bad you're not closer, I have a complete e-body with 11" backing plates & 3.55's and the perches already moved in 1" for Dr Diff relocation I'm looking to get $400 for.

[redo1973]

Thanks again.  You guys on this site are awesome.  You just saved me a bunch of money.  I saw rebuilt 3.23 chunks at the Columbus Nats for $450 but they are in Pennsylvania.  I'll keep looking.

[Chryco Psycho]

Hard to say what you are buying with used parts , I answered an ad for sure grips , I told him I would buy all 4 as long as I could check them out , they were all cone type & all worn to the point the cones were bottomed out inside the case / junk
 Gearsets typically sell for $400 & up & you can bet the sure grip is beat , you could install new gears & brgs in what you have for around $450 .
 $ spd conversions get expensive , buying all the parts you can easily hit $3500 or more but buying parts smart / used you can save a lot of that cost but the trans is $00 , a new clutch can run that much as well , don't use a used one [my clutch & flywheel was $1100] , the belhousing can be $400 for a good one  & you still need a lot of other parts .