66 dart rear end swap

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David66dart

David66dart

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I have a 66 dodge dart and I have what I believe to be a 7 and 1/4 Rear end and have found that it will not hold the power of the swap I am doing from slant 6 225 to a 318. I was wondering what rear end I should use. I was thinking a ford 8.8 might work but I don't know how I would go about shortening it or anything. So what rear end would you recommend. It's My first engine swap and needing some help. Also if you know where to find tranny mounts for a 727 that would be great. But basically what's an easy and cheap way to put a new rear end in my dart. I am guessing the 73 f250 rear end I have won't work lol.
 
Ill take a stab at this.

The easiest is to find a donor car same year and model with an 8 3/4 rear, driveshaft, shock plates, u joints etc.

The 73 f250 rear you have have could be shortened and reworked to fit but it would be the same work as an 8.8 ( i'm assuming it is a ford 9") but if it is a full floating Dana 60 or the like there would be more work involved.


Depending on what you are planning to do with the car and HP out of the engine you could just stick with the 7 1/4. There are many members who have put HP into a 7 1/4 with out issue.

There are lots of vendors (Cass at Dr. Diff) who will sell you a fully rebuilt rear the correct size and be a bolt in.

ultimately if you want to do an 8 3/4 swap you will need the following:


8 3/4 center section (like the 3dr member on a ford 9") with the correct size input yoke for the u-joints
A-Body 8 3/4 axle housing
A-body 8 3/4 axles (small bolt pattern to match your front wheels)
You can reuse your 7 1/4 brakes ( most likely)
brake line for the housing
brake line terminal block
Axle vent bolt
flexible brake hose from axle housing to body ( diferent depending on the year of the housing)
8 3/4 U bolts
8 3/4 Spring perches
U joints
Drive shaft


Looks like you want to change the transmission too

transmission
proper sized output yoke for the u joints
mounts
kick down linkage (not 100% sure of that)
flex plate ( not 100% sure of that)

NONE of this is cheap.
you can see where a donor car might be cheaper.


Good luck to you.
 
Last edited:
David66dart said:
I have a 66 dodge dart and I have what I believe to be a 7 and 1/4 Rear end and have found that it will not hold the power of the swap I am doing from slant 6 225 to a 318. I was wondering what rear end I should use. I was thinking a ford 8.8 might work but I don't know how I would go about shortening it or anything. So what rear end would you recommend. It's My first engine swap and needing some help. Also if you know where to find tranny mounts for a 727 that would be great. But basically what's an easy and cheap way to put a new rear end in my dart. I am guessing the 73 f250 rear end I have won't work lol.
Click to expand...
Ya, your F250 rear probably has 8 bolt wheels. Don't even go there for a swap. Do like Dana suggested or use search here for Ford 8.8 swaps. They are large bolt circle and will be a different bolt circle than your fronts unless they also have been changed.
 
Dana67Dart said:
Ill take a stab at this.

The easiest is to find a donor car same year and model with an 8 3/4 rear, driveshaft, shock plates, u joints etc.

The 73 f250 rear you have have could be shortened and reworked to fit but it would be the same work as an 8.8 ( i'm assuming it is a ford 9") but if it is a full floating Dana 60 or the like there would be more work involved.


Depending on what you are planning to do with the car and HP out of the engine you could just stick with the 7 1/4. There are many members who have put HP into a 7 1/4 with out issue.

There are lots of vendors (Cass at Dr. Diff) who will sell you a fully rebuilt rear the correct size and be a bolt in.

ultimately if you want to do an 8 3/4 swap you will need the following:


8 3/4 center section (like the 3dr member on a ford 9") with the correct size input yoke for the u-joints
A-Body 8 3/4 axle housing
A-body 8 3/4 axles (small bolt pattern to match your front wheels)
You can reuse your 7 1/4 brakes ( most likely)
brake line for the housing
brake line terminal block
Axle vent bolt
flexible brake hose from axle housing to body ( diferent depending on the year of the housing)
8 3/4 U bolts
8 3/4 Spring perches
U joints
Drive shaft


Looks like you want to change the transmission too

transmission
proper sized output yoke for the u joints
mounts
kick down linkage (not 100% sure of that)
flex plate ( not 100% sure of that)

NONE of this is cheap.
you can see where a donor car might be cheaper.


Good luck to you.
Click to expand...

DAMN - I have a 63 Valiant and wanted to put in a 318...I bought the wrong damn car.
 
Jeff 63ValiantConvertible said:
After reading your response to the other fellow, I find that my 63 Valliat will require more fabrications and customizations than I thought...thank you for sharing your experience on the rebuilds.
Click to expand...
Swapping out a 7.25 rear for an 8.75 is very simple. Can be alittle costly but it’s pretty basic. Would just need shorten driveshaft.
 
318 in a early A is not a lot of trouble
You just need the right parts.
 
Dana67Dart said:
318 in a early A is not a lot of trouble
You just need the right parts.
Click to expand...
Thanks...my problem is knowing all the pieces to the puzzle. I enjoy reading the posts in this forum, but sometimes too many different paths to get to the top of the mountain...could you possibly breakdown what I would need...I have the following:
V8 Motormounts
V8 Centrelink
Throttle Body Linkage for V8
318 Engine
727 Transmission, which someone said if I get a 904 for V8 I wouldn't have to change my driveshaft length
I have been told that my stock 7.25 rear end will blow up, told to get an 8.75 from 66-72...No luck, but told an 8.8 Ford would work, found a ford 7.5 same width...will this work?
Told I would have to modify the firewall due to the wiper motor on 63 Valiant.
Told different things about Radiator...I don't know
Are there items that I am not seeing in these posts?
I guess now you see my dilemma.
Thanks for any help you can give...
 
Dartsun said:
Swapping out a 7.25 rear for an 8.75 is very simple. Can be alittle costly but it’s pretty basic. Would just need shorten driveshaft.
Click to expand...
Thanks...I have a welder mechanic friend who is willing to do the work, but said will be a lot of time and work...ie fabrication and customization. He is a Ford and Chevy man (but I don't hold that against him..Ha) so he says he is not too familiar with the work needed...a lot of time figuring...he said I should have chosen something other than a unibody...Depression.
 
is the car drivable now?

How rust free is it? converts typically don't fare as well as HTs

the 67 dart (bigger and heavier) came with a 273 v8 and a 7.25 (mine has been in use for 319,000 miles behind my 273)

when it comes to fabrication I dont think it will be all that much if you can find the OEM parts for a stock 63-64 V8 car. (ASSUMING the 36 and 64 share the same body)


I assume your car is a \6

looks like in 64 the valiant came with a V8 so ASSUMING the 63 and 64 were the same body. it will be a bolt in as long as you use some earlier parts on the engine. the timing cover, cast iron water pump with the drivers side outlet and the associated bracketry.

that way you can put the stock V8 radiator in it
 
There were plenty of cars that came 318/7 1/4”. It will hold up fine if you don’t put to much HP on front of it.
 
The 63s weren’t designed with the V8 in mind. I believe the wiper motor gets in the way. Some people swap to a smaller one or modify the firewall. There is a lot of threads about it on here.
 
Dana67Dart said:
is the car drivable now?

How rust free is it? converts typically don't fare as well as HTs

the 67 dart (bigger and heavier) came with a 273 v8 and a 7.25 (mine has been in use for 319,000 miles behind my 273)

when it comes to fabrication I dont think it will be all that much if you can find the OEM parts for a stock 63-64 V8 car. (ASSUMING the 36 and 64 share the same body)


I assume your car is a \6

looks like in 64 the valiant came with a V8 so ASSUMING the 63 and 64 were the same body. it will be a bolt in as long as you use some earlier parts on the engine. the timing cover, cast iron water pump with the drivers side outlet and the associated bracketry.

that way you can put the stock V8 radiator in it
Click to expand...

Thanks for the information...I'll try and find parts that you have suggested.
 
The bump in the firewall can be removed and replaced with a flat panel. The wiper motor is not in the way there is nothing behind the bump. In my 63 Valiant I just heated it red hot with a torch and just pushed it in. I did a 273 conversion in mine. Most of the parts are 68/69 dart.you will also need a center sump oil pan.
 
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