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driveshaft length

RSZ28

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Swapping a big block in by early B Body, so the driveshaft will need to be shortened. I know that if I had a slip joint, the driveshaft length would have to be calculated for suspension travel. However, I need to shorten a ball and trunnion style driveshaft. This has a flexible boot that compensates for the travel. How do I determine length? Thanks
 
look at this chart

View attachment 397979

mopar driveshafts.jpg
 
Thanks Brian6pac, but the attachment will not load. Does the chart show pre-66 models that use the ball and trunnion universal? If not, I don't think it will help me. A slip yoke moves in and out at the back of the transmission to allow for suspension travel. The slip yoke is bottomed in and then pull out a measured distance. From this point, you take measurements from the slip yoke back to the yoke on the rear end to determine driveshaft length. The yoke on my transmission is held on by a large washer and nut and doesn't move, so I need to know if the flexible boot on the driveshaft needs compressed and if so, how far to allow for suspension travel.
 
looks like it starts at 66 up you can click on the chart and it will get bigger, I had real problems loading it it's always small.
 
Too bad you werent closer, id give you my old trunion driveshaft, as a spare in case yours got fubared. Id bolt it to the tailshaft, make a witness mark on the tube, measure the distance from tailshaft flange. Pull driveshaft back as far as it can go and measure the distance from flange to witness mark. Id push the driveshaft back in an pull it out so its only been extended bwtn 3/4 and 1 inch. Then measure from your witness mark to leading edge of axle u joint. To see a ball park length. Your local driveshaft place will probably be able to make up a slip joint style driveshshaft, and you get rid of ball and trunion once and for all
 
Guys RSZ28 doesn't have a slip yoke trans.
When you have engine and trans in car then measure driveshaft length. Don't know if these is the right way!
Put car on j stands front and rear the rear j stands should be under rear axle tubes to have weight on rear suspension and car almost level. Attach drive shaft to trans push drive forward and mark d shaft on center of yoke u joint cup. Pull d shaft to the back and mark center line of yoke u joint cup. In the middle is where the center of yoke u joint cup should be. This allows equal up and down travel. Hope it's clear?
 
Thanks Fran. See if I got this right. (1) Bolt the drive shaft to the flange on the rear of the transmission and push forward until it can't go any farther and the flexible boot compresses, this should move the pin that is inside the body flange on the driveshaft rearward until it bottoms out (2) mark driveshaft at the rear of the car using the center of the universal yoke (3) pull the driveshaft rearward until the flexible boot is stretched and the pin moves forward and touches the dust shield (4) mark driveshaft at the rear of the car using the center of the universal yoke (5) midway between the two marks should be where the center of universal yoke on the end of the driveshaft should now be located

I looked in a parts catalog and saw that the drive shaft for a big block B body should be 53 1/2". I will check and see if this is close to the measurements above.
 
Yes you've got it. Don't forget about having Jack stands the way I described. The rear suspension can't be hanging so jack stands have weight on rear axle. and front must high enough so it's level. Measure several times "Measure twice cut once". A helper wouldn't hurt.
 
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