Driveshaft length

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Austin Schlegel

Austin Schlegel

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Westfield Indiana
I am trying to determine the driveshaft length for my 68 barracuda with a 904 and 8 3/4 rear end. I have the slip yoke in the transmission and have measured the back of the uj hole (like in the picture attached) to the back of the pinion yoke. Which came out to be 50 3/4". My user manual says that the driveshaft length is 49.27" which is not what I measured. Am I measuring wrong? Or could the manual be wrong?

Thanks

Inked1015211023_LI.jpg
 
Normally you measure center to center of the u joints for factory shafts.
If you are looking to have a custom driveshaft made, check with your supplier as to how they prefer the measurements be taken.
 
Professor Fate said:
Normally you measure center to center of the u joints for factory shafts.
If you are looking to have a custom driveshaft made, check with your supplier as to how they prefer the measurements be taken.
Click to expand...

Oh so that's how they came to 49.27 then?

Id rather not have a custom driveshaft made. Id like to save the money and go with factory one, just wasnt sure if it would fit.
 
When you pull your measurement, make sure to bottom out the transmission yoke, then pull it out .75-1". In your picture, it looks like it's way too far inward.

As mentioned, driveshafts are typically measured u-joint center to center.
 
As stated. Center line to Center line CL to CL with yoke 3/4" to max of 1" pulled out after bottoming in transmission tailshaft. AND the vehicle loaded on it's suspension. Do not measure on a lift with the axle hanging on sagging springs.
 
Be sure to include the u-joint size needed on the driveshaft end for the yoke. Probably 7260, but not something to take for granted.
 
did any A body come from the factory with a 904 and an 8 3/4? i don't think so, so any factory driveshaft fitting is just luck. also, U joint sizes matters. there' s a little room for variation in length but not much
 
So I was looking at Denny's driveshaft for a custom driveshaft. They seem nice but a little pricey for this old rust bucket. Has anyone ever bought from them?
 
kursplat said:
did any A body come from the factory with a 904 and an 8 3/4? i don't think so, so any factory driveshaft fitting is just luck. also, U joint sizes matters. there' s a little room for variation in length but not much
Click to expand...

Im not sure what came from the factory. The service manual only specifies the engine and not the transmission. Example: 318 with auto trans .... 49.27"
 
Austin Schlegel said:
Im not sure what came from the factory. The service manual only specifies the engine and not the transmission. Example: 318 with auto trans .... 49.27"
Click to expand...
it say's what trans came with what engine, and what rear end. call a drive shaft place close to you. ask them how they want it measured. then, if you have a shaft that fits, great. if you have one too long, have them cut it. too short, buy a new one. but you need to make sure what the yokes are too
 
kursplat said:
did any A body come from the factory with a 904 and an 8 3/4? i don't think so, so any factory driveshaft fitting is just luck. also, U joint sizes matters. there' s a little room for variation in length but not much
Click to expand...

904 is same length as an A-body A833 4 speed trans, so yes 904 with 8-3/4 is same as A833 & 8-3/4. The driveshaft in my duster with a 904 and 8-3/4 is 49.27" C-C length

727 and 8-3/4 should be 44.99" IIRC

John
 
Quick question here, the yoke into the gearbox... how much of that should be showing? Mines a little excessive..I would have though inch and a half to two from the seal?
 
Wagon of Death said:
Quick question here, the yoke into the gearbox... how much of that should be showing? Mines a little excessive..I would have though inch and a half to two from the seal?
Click to expand...

3/4 inch to 1 1/4 inch max with car sitting on the ground. Also how long is the slip yolk? There are a few different ones.
 
kursplat said:
did any A body come from the factory with a 904 and an 8 3/4? i don't think so, so any factory driveshaft fitting is just luck. also, U joint sizes matters. there' s a little room for variation in length but not much
Click to expand...

Our 71 Dart 318 came with a 904 and 8 3/4
 
Well small issue the transmission won't go into park. So I'm not ready for a driveshaft yet. But when I replace/fix the trans and get a driveshaft installed ill update this feed with the length. I think I'm just gonna call a driveshaft shop and have them cut one for me.
 
Park usually won't work without the driveshaft installed because the output shaft has to turn slightly sometimes for the pawl to engage.
 
Is there a difference between early A body (1965 Barracuda) and the later A bodies when it comes to driveshaft length? I would imagine wheelbase has an influence on the length. I have a 65 Barracuda that is getting a later model 904 and an 8 3/4" rear end. While on the subject, what is the best u joint size to use? The engine is a rather healthy LA (~400hp at the crank) and yes, on occasion I use that hp. (hence the 8 3/4) If anyone has done that swap - a rather common one, I would think - I would certainly be thankful for any information on the driveshaft specs!
Thanks
Cheech/ Art/ R/T
 
cheech14 said:
Is there a difference between early A body (1965 Barracuda) and the later A bodies when it comes to driveshaft length? I would imagine wheelbase has an influence on the length. I have a 65 Barracuda that is getting a later model 904 and an 8 3/4" rear end. While on the subject, what is the best u joint size to use? The engine is a rather healthy LA (~400hp at the crank) and yes, on occasion I use that hp. (hence the 8 3/4) If anyone has done that swap - a rather common one, I would think - I would certainly be thankful for any information on the driveshaft specs!
Thanks
Cheech/ Art/ R/T
Click to expand...

They are the same, Barracudas and Dusters for your early A. 67 and up just stretched the front forward from the engine.
 
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