8 3/4 Rear End Conversion

[money pit]

I have a 70 barracuda with a slant six. I'm converting to a 360. I have the engine, 727 trans, the K member, and the rear end with posi from another E body. Can I use the old leaf springs and U bolts. Can I just get a drive shaft from another E body with a small block and 727 trans or do I need to measure and get a new drive shaft? Or can I use the old drive shaft. I had a 904 trans with the slant. I don't plan to race it, just a daily driver. Thanks

 

[Cudafor36]

I believe the entire rear is the same if it was a slant six or v8. Changing the pig and upgrading to the 727 might require a new drive shaft but you need to know the length difference between the 727 and 904 and how it was placed in the car. My gut tells me it should be shorter with the 727. Not much help I know.

 

[Adam]

The drive shaft lengths are listed in the service manual, mine is in storage or I would look it up for you... but it is probably online somewhere.

FYI, I believe a Challenger is an inch or two longer than a Barracuda, and the difference is in the floor pan. So all options being equal a Challenger drive shaft may be too long.

My Mopar.com has the service manuals available as zip files.

 

[aussiemark]

Wouldn't the slant have a 7 1/4 diff? my 318 Barracuda had one. If it does then you will need to change the u bolts and the shock mount plates. You would be better to change to at least S13 spec suspension with a sway bar.

 

[SFEbody]

You can use the old drive shaft but will have to have it cut down and balanced. I did that to mine when doing the exact same swap. Not pricy either, local drive shaft shop charged me less than $100

 

[money pit]

I believe the entire rear is the same if it was a slant six or v8. Changing the pig and upgrading to the 727 might require a new drive shaft but you need to know the length difference between the 727 and 904 and how it was placed in the car. My gut tells me it should be shorter with the 727. Not much help I know.

I think you"re right. The 904 trans has a short tail shaft and the 727 has a longer tail shaft which means I would need a shorter drive shaft. Thanks

 

[money pit]

The drive shaft lengths are listed in the service manual, mine is in storage or I would look it up for you... but it is probably online somewhere.

FYI, I believe a Challenger is an inch or two longer than a Barracuda, and the difference is in the floor pan. So all options being equal a Challenger drive shaft may be too long.

My Mopar.com has the service manuals available as zip files.

Thanks I'll check out the website.

 

[money pit]

Wouldn't the slant have a 7 1/4 diff? my 318 Barracuda had one. If it does then you will need to change the u bolts and the shock mount plates. You would be better to change to at least S13 spec suspension with a sway bar.

Yes, I do have the 7 1/4 rearend in the car now. Thanks for the info.

 

[money pit]

You can use the old drive shaft but will have to have it cut down and balanced. I did that to mine when doing the exact same swap. Not pricy either, local drive shaft shop charged me less than $100

I leave in So Cal. I leave near Pasadena. Where did you take your drive shaft to be shortened? Thanks

 

[/sixchall]

MoneyPit........I made the same conversion you are referencing on my ‘70 Slant6 Challenger. Exception is I retained the 6 under hood. 20 years ago the 7 1/4 gave out and I was able to pick-up an 8 3/4 742 case single legger w/ 3.23 gear set for $50.00 drum to drum. It bolted up to the springs using all the original spring plates and bolts, no problems. I have a 904 behind the 6, I did have to shorten drive shaft and had it rebalanced, at the time it cost me $20.00 at DGA Machine here in Riverside Ca. However I believe they have closed up. But there is a well known driveline business in Corona Ca. that does all the classics, hot rods and customs here in the south land. By the way my Dodge has been driving quite well with my conversion.

 

[moparleo]

Blairs' Speed shop in Pasadena has been there since the 40's and has a complete machine shop. I have had several drive shafts built there. The springs on most any 40+ year old car would most likely need replacement even without a driveline swap.

 

[money pit]

Blairs' Speed shop in Pasadena has been there since the 40's and has a complete machine shop. I have had several drive shafts built there. The springs on most any 40+ year old car would most likely need replacement even without a driveline swap.

Thanks, I didn't know they did drive shafts.

 

[340challconvert]

As several people noted; change out the leaf springs.
The original factory leaf springs for an e body 340 car would have been 3400044. Your originals would probably not be up the the job, especially since they are very old. There are several good options here; PST and Mopar- formance carry springs. Firm Feel also has springs that are considered excellent #149356.
Here's a great article on rebuilding the leafs from Mopar Connection: http://moparconnectionmagazine.com/gallery-get-sprung-restoring-your-leaf-springs/
I picked up the Mopar Performance XHD units from Jegs with free shipping for my A66 Challenger.
There are more options out there, even for stock / driver applications.
Sidebar note: e bodies always sat low in the rear, there are companies that sell springs at different spring levels that offer a slight raise in car height if you like.
Definitely address the old springs on the car and good luck.

 

[Daves69]

You might check your slip yoke fit in the new trans.
Some dims from the MP Chassis manual...…….

 

[doctorgoo]

I have a question, I have a 1973 340 cuda with a factory antenna in the rear , is that possible?