Dana 60 to 8 3/4 Rear swap question

[Mopar426power]

My son is going back to an 8.75 rearend from a Dana 60 in a 70 Challenger 4-speed car, will we need a new driveshaft?

 

[Katfish]

Yes, Dana is larger, typically 1.5” difference

 

[Mopar426power]

He tells me that length seems OK but has U-joint issues, maybe yokes are different sizes?

 

[Katfish]

There are 2 yoke sizes, Dana would take larger. Make sure the yoke isn’t pulled out too far or you’ll have vibrations

 

[pschlosser]

I believe they have the correct yoke in the current driveshaft.

 

[Katfish]

For clarification, the only difference in the yokes would be the u-joint size.
There are small 7260 and large 7290 u-joints
The 8.75 will need a longer DS compared to the Dana.
So you may be ok

https://postimages.org/][/url]

 

[pschlosser]

The OP says he's going the other way, from a dana to an 8.75 which implies they need one longer.

I checked the parts book, and I cannot, for the life of me, find a distinction between propeller shafts on differing rear axles. It all seems listed by engine and transmission.

 

[Chryco Psycho]

The length will probably work but it is not right , the slip yolk will be too far out of the trans ,it needs to over 1" longer for the 8 3/4

 

[pschlosser]

it needs to over 1" longer for the 8 3/4

My notes suggest 1.11 inches. But I cannot confirm via the parts book nor can I find any part # for a propeller shaft with a 9.75 (Dana 60)

 

[Katfish]

Check here

Drive shaft length for a 1970 Challenger with Hemi and Dana

 

[Mopar426power]

Thanks, I will check measurements this weekend.

 

[pschlosser]

The parts book shows the propeller shaft lengths for 9.75 Rear Axle, either 727 (auto) or 833 (manual) transmission:

Barracuda #2883774 42.60
Challenger #2883667 44.60

And for the 8.25/8.75 Rear Axle, either 727 (auto) or 833 (manual) transmission:

Barracuda #2883636 43.60
Challenger #2883656 45.60

The Dana 60 9.75 drive shaft is 1.00 inches shorter.

 

[AkBillyBow]

If I may ask, why would you go from a Dana 60 to the 8.75? I am considering going the other way. Other than putting a car back to it's original state, is there some big disadvantage to the Dana 60? Not bashing anyone, just curious to know so I won't make a mistake I may regret later.

Thanks !!

AkBillyBow

 

[Katfish]

Less weight?

 

[Chryco Psycho]

Hardly , maybe 50Lbs difference , & usually better traction with the Dana .

 

[Mopar426power]

Long story but to answer the question: yes, the Challenger has a 340 and we wanted the original 8.75 rear back in the car.

 

[Dodgeboy]

In drag racing some people will switch from the 8 3/4 to a Dana. The weak link in the 8 3/4 seems to be the location/relationship of the pinion/rearend gear. On a good launch (lots of torque/traction) the pinion will try to climb the ring gear causing the diff to flex @ the pumpkin, breaking gear teeth. Using a pinion snupper helps prevent the flexing. Some guys have this issue, others don't. The Dana has a better location of the pinion gear so this is not a issue. I do not know what torque level or 1/4mile et that will test the limits of the 8 3/4. Seems it could be low 10sec or 9 sec ets

 

[Chryco Psycho]

I used to grenade about 1 8 3/4 diff / year running mid 11s with a 4 spd

 

[Dodgeboy]

I have never understood why it seems like 8 3/4s don't get along with manual transmission's. Does a clutch just shock the drivetrain that much more then a high stall converter?