69-70 C body rear ends.

[BrooklynBeer]

Starting the brain work on the latest of a new project. Finishing up a 1970 D200 farm field find.

First off i don't have a car yet. But i am beginning the search for a 69-70 Fury. Or a same year Polara or even a 300.

Goal is going to be to make a step above factory street car in performance. (Think Fury GT) Just enough cam to know it's there, late model open chamber heads, no more then 10-1 for 92 oct fuel and most likely go EFI. (I have never done EFI)

Every 3 years i start something new.

Being most of these cars I am seeing are non sure grip, what rears are a direct swap or am I looking and just swapping a sure grip into the factory rear?

My only C body experience is the 63 Dodge 880 I use as a parts runner with push button and 361.

 

[Davea Lux]

The third members on all of the 69-70 C-Body 8.75" rear end will interchange, do not waste time on trying to build an 8.25" rear end. For serious performance you should use the Dana 60 rear end. A big block car will have the larger diameter u-joints. If you are going for moderate performance you will want either a 3.23 or 3.55 gear ratio. Most 69-70 C-Bodies are heavy enough to where turning the tires over is not that much of a problem unless you are going for 400 or more horsepower.

Dave

 

[BrooklynBeer]

The third members on all of the 69-70 C-Body 8.75" rear end will interchange, do not waste time on trying to build an 8.25" rear end. For serious performance you should use the Dana 60 rear end. A big block car will have the larger diameter u-joints. If you are going for moderate performance you will want either a 3.23 or 3.55 gear ratio. Most 69-70 C-Bodies are heavy enough to where turning the tires over is not that much of a problem unless you are going for 400 or more horsepower.

Dave

Thank you. Just finished up going over the dana in the D200. I was wondering what i should be looking for as a direct swap?

 

[Davea Lux]

Thank you. Just finished up going over the dana in the D200. I was wondering what i should be looking for as a direct swap?

The pickup rear end is wider and you will likely need to reposition the spring perches. If your Dana has 5 hole wheels on it, it was for low GVW applications and will not be the full floating type. We used an 8 lug full floater Dana in some of the racers years ago. As I recall, we had to shorten the axle tubes and the axles for racing applications that specified full floating rear ends. The D 200 usually came with 4:10 gears which are going to be unsuitable for street use with an automatic, your engine will be beating it self to death.

Dave

 

[BrooklynBeer]

The pickup rear end is wider and you will likely need to reposition the spring perches. If your Dana has 5 hole wheels on it, it was for low GVW applications and will not be the full floating type. We used an 8 lug full floater Dana in some of the racers years ago. As I recall, we had to shorten the axle tubes and the axles for racing applications that specified full floating rear ends. The D 200 usually came with 4:10 gears which are going to be unsuitable for street use with an automatic, your engine will be beating it self to death.

Dave

I have no dreams of using this dana from the truck in a C body. It has 8 lug axles to start and factory 3.54's. Basically this truck fell into my lap and i used it as a learning tool in rebuilding the 727. Just curious as to what other rear could go into the 69-70 C body that is a little beefy but not needing much work on it to see it happen

 

[Blusmbl]

There is a chart on a bunch of different sites that show the rear axle width changed from 69 to 70 for C bodies but I don't know how accurate it is. I know for sure the 65-68 C body rearend is 56 3/4" and 46" perch to perch, which is almost identical to the 70-74 E body rearend. The chart shows that 65-69 are the same and 70-73 C body are the same, but that is a little suspicious because the C body changed body styles and went from slabside to fuselage in '69.

 

[Big_John]

There is a chart on a bunch of different sites that show the rear axle width changed from 69 to 70 for C bodies but I don't know how accurate it is. I know for sure the 65-68 C body rearend is 56 3/4" and 46" perch to perch, which is almost identical to the 70-74 E body rearend. The chart shows that 65-69 are the same and 70-73 C body are the same, but that is a little suspicious because the C body changed body styles and went from slabside to fuselage in '69.

There were some changes from 1969- 1970. If you look at a 1970, the shackles are offset and the shackle mount is wider.

From what we've been able to figure in past discussions, the 1970 rear is 1 1/4" wider than the 1969 rear and the shackles are offset 5/8" on both sides.

FWIW, in 1970, they started using the rubber mounted front stub frame on some cars, although IIRC, the 1970 Plymouth got the solid mount stub frame in all their cars. Also, the shackles for 1970 aren't available new anywhere, but that's getting off the subject.

 

[Blusmbl]

There were some changes from 1969- 1970. If you look at a 1970, the shackles are offset and the shackle mount is wider.

From what we've been able to figure in past discussions, the 1970 rear is 1 1/4" wider than the 1969 rear and the shackles are offset 5/8" on both sides.

FWIW, in 1970, they started using the rubber mounted front stub frame on some cars, although IIRC, the 1970 Plymouth got the solid mount stub frame in all their cars. Also, the shackles for 1970 aren't available new anywhere, but that's getting off the subject.

That makes sense, thank you!

 

[fury fan]

Older thread, but worth to mention for future readers:
A Dana is overkill for 98% of us. And if it came from a truck, it's an 8-lug floater, and those are expensive to convert for car use, lots of mods needed.
I've never seen/heard of the Dana used in 1/2-ton trucks as a 5-lug.
If you find a car version, it'll be pricey - $2000 and up seem to be the askign prices as they all came from Super-Trak-Pak 4-speed musclecars.

And the Dana 60 absorbs more HP than other comparable 'strong' axles.
Even Hemi automatic cars got the 8-3/4 unless certain option boxes were checked.
If you really think you need more than an 8-3/4, look to a Ford 9". You can buy it mail-order, built to your specs. (but it'll be pricey, too)

The 8-1/4" started appearing in 69 C-bodies behind smallblocks. Any bigblock car should come with an 8-3/4, although in 72-73 there might be some exceptions behind a 400-2?

If you get a truck 8-3/4, the spring perches are probably on the top of the axle tube, so they'd need relocated.
Also be aware, that some, if not all, truck 8-3/4 center sections are not set up for a pinion snubber. Whether the bosses are cast in but undrilled - I do not know.
I just know that trucks didn't get pinion snubbers.

Also - I believed that the 69 Polara/Monaco got a narrower axle than later years. I do not know whether this is true of 69 Plymouths. @71Polara383 - can you confirm?

 

[Blusmbl]

I put a Dana in my '68, what swayed me from the 9" to Dana was if I went with the 9" I would've needed a new driveshaft. The Dana's snout was close enough that I was able to get my original 3.5" driveshaft cut down. The aftermarket definitely favors the 9" though, and starting from scratch it's the smarter option.

4 speeds with a > 4000# car and drag radials would benefit a dana or built 9". My car is an automatic, has gone 11.30's with the 8 3/4 but I wanted it to be bulletproof and it's getting a 540 this year, so I went with the overkill option, have broken a bunch of rearends in previous cars and figured the peace of mind was worth it.

It also didn't slow down at all going from a 8 3/4 to the Dana, it gained something like 60# and I changed from 4.30 to 4.10 gears, but it ran the same or better ET's after the swap.