Drivetrain advice for engine swap

-
MRGTX

MRGTX

Well-Known Member
Joined
Sep 24, 2007
Messages
2,198
Reaction score
728
Location
CT, USA
Hey, guys... I have had my Dart Sport for 11 years and I am ready to swap out the 318 for something with a bit more muscle.

I have a few basic questions that may reveal some ignorance on my part so any advice would be appreciated.

Right now it has the 7 1/4" rear and the 904 trans...which probably wouldn't live long behind a 360 crate motor...

I think I have found a source for hopped up 904s that will handle 500 hp. so that seems to be do-able but the rear end still has me puzzled.

What is the usual route that people go when upgrading the rear? 8 1/4" rears are nowhere to be found around where... and it seems that 8 3/4" rear axle assemblies are somewhat easy to find but they're pretty much always from B and E bodies which are obvioulsy to long (wide?) for the A-body.

Any sources for new rear assemblies (case/axles/chuck/everything?)

Thanks so much for any help!!!
 
The HP to 904 discussion comes up here often and the concensous has been the 904 will handle whatever you throw at it after a quality rebuild. As far as the rear, hang around here awhile somebody will have one for sale, I've seen 8 3/4 rears go from 300 to 1200 complete. A big spread so if you watch for a while you could get one somewhere in between. The B and E housing can be cut and refitted with aftermarket axles or the axles can be reworked as wll as the case. A Ford 9" is also an option. You can get them from Explorers and Rangers some with disc brakes.
 
MRGTX said:
.
What is the usual route that people go when upgrading the rear? 8 1/4" rears are nowhere to be found around
Click to expand...

8-1/4
There are the most popular rear to find in an A body car and the rear was installed in them longer and later than other rears.
The 8-3/4 is a popular unit that can be found at a decent price if you wait for it to come along. Bargin hunting was never my thing. (As well as payin to much for it.)
I forget whom does it, but you could order one from Moser I think to bolt in. But thats the 9-3/4 Dana rear for something like 1300+ bucks.
I got my 9-1/4 for $200 w/a 3.21 suregrip in there allready.
 
This forum rocks. You guys are great!

rumblefish360 said:
8-1/4
There are the most popular rear to find in an A body car and the rear was installed in them longer and later than other rears.
The 8-3/4 is a popular unit that can be found at a decent price if you wait for it to come along. Bargin hunting was never my thing. (As well as payin to much for it.)
I forget whom does it, but you could order one from Moser I think to bolt in. But thats the 9-3/4 Dana rear for something like 1300+ bucks.
I got my 9-1/4 for $200 w/a 3.21 suregrip in there allready.
Click to expand...


Good stuff to know... thanks.

How much power is the stock 8/14 rear good for? Can you tell if its a Suregrip by looking at it?

GTGrinly said:
... A Ford 9" is also an option. You can get them from Explorers and Rangers some with disc brakes.
Click to expand...

This is an extremely interesting option... is the axle a direct swap in? What modifications does this require? I knew Explorers were good for something!
These even come with a 4.5"x5 bolt circle, no?
 
I would not run a 8 1/4, seen to many problems! First off they have a "C" clip axles, the center section breaks loose from axle tubes. 8 3/4 is your best bet!! I have run a 9" in them before, cheap and easy swap for a duster, get one out of a early 70's mustang they are 54" inside backing plates. Which is 3" wider and the wheels line up with the front. Also don't have to move the spring seats. But does not work for dart, scamp. If you wait at the right time and be patient you can pick a 8 3/4 up for $300.00-$700.00 if you just look and ask around. If you go with the 904 trans you don't have to swap the drive shaft!! Hope this helps, you also can get a short block crate, edelbrock heads, intake etc a little cheaper than the whole crate motor!!
 
I was wondering about the same info to put into my 71 Duster with a 440. I happen to know someone who has several rear ends & I had planned on asking here which one to ask him for. As far as the moving the spring seats on the ford 9" what if you moved the springs in for a minor tub?
Is the 8 3/4 a better option that a 9 1/4?
sounds like the ford 9" would be the easiest, but I don't know if I can put ford parts into my Mopar.
 
GTGrinly said:
.. A Ford 9" is also an option. You can get them from Explorers and Rangers some with disc brakes.
Click to expand...

Are you certain about this? I just called the local junk yard and they said that the last 9" rears were from the early 80's and that the Exploder had an 8.8" rear.

Perhaps that 8.8" is useful?
 
Rangers and Explorers are 8.8's and have axle tube to housing problems. As far as a '70s Mustang 9" I think you will have better luck finding an 8 3/4 out of an a-body. Most Mustangs had 8" rears and the 9" ones fetch more dollars than an a-body 8 3/4. Although c clip rears are my less favorite an 8 1/4 is plenty up to the task of a mild street car. I have one in my BB Cordoba and it is still alive.


Chuck
 
I sure would not install a 9 1/4!!!!!!!! Maybe a 9 3/4 = Dana 60!!

I know I did not fill very good with cross breading either but for 200.00 drum to drum versus 700.00! Gears, posi, & axles are cheaper as well. I'm still mopar at heart!!!!!!!!!!!

Most Mustangs in 70-73 had 9" just had to put that in there!!!! 60's hard to find 9" in a mustang!!
 
I apologize for the mis-info...I know better then to repeat what I'm told til I verify it.. but didn't this time. My neighbor built a Cobra and he said he used a 9'' Explorer rear with discs, so I find he was misinformed as well. I have used 9'' in dirt track cars, had them cut to fit and axles resplined for $135.00, but that too was 10 years ago. And thank you all for setting me straight.
 
MR.GTX, it's the torque that will kill the rear. Not the HP. The 8-1/4 is up to most street duty, no problem. Loyd 360 says to many problems. I haven't seen any problems in street cars. Never once. He makes a mention of the C-clip in the rear. The weak point. If this C-clip breaks, the axles with tire can slide out of the tube. This IS a dangerous thing. However, since your not racing and a mello create engine is all it will see, I can not find a problem in use of a C-cliped rear. The only other rears that are NOT C-clip are the 8-3/4 and Ford 9.

I do not have a torque rating that the 8-1/4 fails at. Loyd360 seems to have an adversion to C-clip rears. I can understand that, once bitten, twice shy.

While a 8-3/4 is a great idea, bucks can get in the way. Or lack there of. Same with the 9-1/4. While a bigger ring and pinion can hold more power, the rear isn't very popular and ring and pinion ratio's are in short surply when it comes to verity. Shorten this rear is a thing I have never seen. While in theroy, a good canidate, for the cost, you may want to look into an entire DANA assembly that will bolt in for a few bucks more.

By the time you referbish the rear and upgraded it with new parts, the DANA bolt in is a sweet deal. All new and ready to go.

Loyd360 also said;
you also can get a short block crate, edelbrock heads, intake etc a little cheaper than the whole crate motor!!
Click to expand...
I went this route. It is a good idea. I did a MoPar create short block (JUNK!!!!!) and the Edelbrock heads and intake with a Carter 750 afb, Hooker super comp headers. Theres some fellas here that run low 12's in there A bodies with this set up. This set up is in my E-body Cuda. No times. Just run the street.

The cost of this build isn't in my head, but, since I was getting discounts through the MoPar club and wisely argued at the speed shops there prices vs. Jegs and other speed shop bigs prices, I offered cash while purchasing alot of things at once. They like cash and are happy to fold up some green backs right into there wallet without being taxed.

Shop wisely and save. Talk to the counter peoples and ask for there boss on a cash purchase. Be willing to deal.
I got my Edel. heads intake and everything (Short block up)to blot it on and go for $1300.
 
Here’s a low cost approach that workers good for me.
Not as good as an 8 ¾ but lots cheaper.
Don’t know about your budget.
The 8 ¼ is pretty strong.

A Diplomat 8 ¼ will be a little wider than an A-body 8 ¾ and it will improve handling and aesthetics in your Sport/Duster.

All you have to do is move the spring perches. The locating hole is bigger but just weld a couple of fender washer in.
I’ve got how-to pictures.
I’ve done the A-body 8 ¾ swap and even with the wider brakes and Moser axles the thing still looks puckered up from the rear to me.

And are you just going to go in a straight line with Green ball bearings on your 8 ¾ or are you going back with tapered rollers like Mother says?
 
This is all good info. How about some clarification for me; I'm just starting my '72 Duster resto.
What years 8 1/4" and from what cars will fit without alterations?
The 8 1/4 from the Diplomat sounds interesting, how about shooting some pics my way:
[email protected]
Thanks!
C
 
look in the tech archive and i wrote up a basic 8.8 swap guide..it's a good one if ou're willing to take your time, it's great esecially if you're gonna do a total rebuild bc you can hook it all up perfect and have a trac loc and discs
 
In the original post, there was no mention of the wheel bolt circle 5 on 4" vs. 4.5".

If I recall all of the 8 1/4" are 4.5" Most (if not all?) of the a-body 8 3/4" were 4".

I would consider bolt circle diameter as another parameter when considering cost between of potential donor rears. Especially if you have to buy new axles with the 4.5" for the 8 3/4"

In my build, I'm switching to 4.5" all the way around. I am starting with the 8 1/4". I plan on upgrading to a narrowed 8 3/4" once I widen my wheel wells and move my spring inboard.
 
Yes all 8 ¾ are the odd bolt pattern. Axles have gone way up to 300 bucks.
Looks like good bearings will run you another 100.
And if you don’t do the axel change, you get stuck with the skinny obsolete brake shoes.

I’ll try and get my 8 ¼ swap pictures scanned into digital this weekend and send it to you
When I documented it years ago all I had was 35mm camera.
I was going to send it in to Mopar Muscle but never got around to it.
It is a good swap. You get the large bolt pattern and a rear that actually fits the car.
Junkyards should be cheap. I used a donor cop car for my engine, trans and rear.
So I had it already.
Just hit the welds of the perches with a high speed and then air chisel the things off. Then re-use them.
I show the tools to use in the pictures and how I set the pinion angle. That information is in the Sheppard chassis manual. But I think you could just use the original locations for that. Just move them out to the correct width for an A-Body. I actually put the rear up on the springs and tacked the perches in position. I used the car as a jig.
Then took it out and welded down to get a good weld.
I used a wire feed. You don’t need a lot of heavy stuff.
I think a Diplomat is an M body? And an F body is the same width flange to flange.
But I’m not sure off hand.
I run 15 inch tires too.
 
adriver said:
Yes all 8 ¾ are the odd bolt pattern. Axles have gone way up to 300 bucks.
Looks like good bearings will run you another 100.
And if you don’t do the axel change, you get stuck with the skinny obsolete brake shoes.

I’ll try and get my 8 ¼ swap pictures scanned into digital this weekend and send it to you
When I documented it years ago all I had was 35mm camera.
I was going to send it in to Mopar Muscle but never got around to it.
It is a good swap. You get the large bolt pattern and a rear that actually fits the car.
Junkyards should be cheap. I used a donor cop car for my engine, trans and rear.
So I had it already.
Just hit the welds of the perches with a high speed and then air chisel the things off. Then re-use them.
I show the tools to use in the pictures and how I set the pinion angle. That information is in the Sheppard chassis manual. But I think you could just use the original locations for that. Just move them out to the correct width for an A-Body. I actually put the rear up on the springs and tacked the perches in position. I used the car as a jig.
Then took it out and welded down to get a good weld.
I used a wire feed. You don’t need a lot of heavy stuff.
I think a Diplomat is an M body? And an F body is the same width flange to flange.
But I’m not sure off hand.
I run 15 inch tires too.
Click to expand...

Please post your pics.... I will be swapping the 7 1/4 out of my Scamp and putting in an 8 1/4 this winter and am interested in seeing how you did it.

Thanks!
 
I got home a little early for the weekend and just sent them to clhyer via email with some notes.
I will try and figure out if I can post them. Seems like a dozen pics.
Can I do that?
I will try and pm them directly to you right now.
Maybe that will work.

Don't see a way to do attachments on a PM.
PM me your email and I'll send them to you in the mean time.

I do remember calling Mopar Muscle leaving a message and offering them the "How To" free. That's why I took pics.
But they never got back to me.
 
adriver said:
I got home a little early for the weekend and just sent them to clhyer via email with some notes.
I will try and figure out if I can post them. Seems like a dozen pics.
Can I do that?
I will try and pm them directly to you right now.
Maybe that will work.

Don't see a way to do attachments on a PM.
PM me your email and I'll send them to you in the mean time.

I do remember calling Mopar Muscle leaving a message and offering them the "How To" free. That's why I took pics.
But they never got back to me.
Click to expand...


PS sent!

Thanks.
 
It turns out that a guy I know has a 8 1/4 rear complete drum to drum.. he's only asking $100 for it

What should I look for? Is there a tag for a gear ratio? How will I know if its a Sure Grip or not? Is it worth buying and rebuilding if its not?
 
If the 8 1/4 is from an A body I'd grab it. It's a simple bolt in deal & the price is right. To check for a Sure Grip, hold one axle to keep it from turning & spin the pinion where the driveshaft attaches. If the other axle turns, it's an open rear (or a totally shot Sure Grip). If you can't turn the two axles independantly of each other, it's a Sure Grip. There might be a tag for the gear ratio, might not.
 
Also, when you get it, sure grip or not, there realitivly cheap units to purchase new bu the way. Just change the gear oil and look on the ring gear for the ratio stamped into the ring gear.
 
rumblefish360 said:
Also, when you get it, sure grip or not, there realitivly cheap units to purchase new bu the way. Just change the gear oil and look on the ring gear for the ratio stamped into the ring gear.
Click to expand...


Thanks... it looks like this thing is pretty much worst case scenario- its from a B-body, no brakes, and its not a sure grip. :sad1:

Still... is it worth $100? Where could I find a suregrip 3.23 or 3.90 chuck?
 
You must log in or register to reply here.
-

Back
Top