Driveshaft shortening question

[1BadDodge71]

Im going to be sending my driveshaft to be shortened but the guy asked some questions which I am confused about.He told me to first measure from the end of the rubber boot to the end of the spline shaft of the transmission.And then measure from the transmission spline shaft to the bolt hole on the yolk of the differential.Is this correct?Anything else i should measure?The transmission is a 727.

 

[redfastback]

THE way to do it correctly is to install the yoke all the way in, measure center to center on the u joint caps, then subtract one inch. The suspension MUST be loaded at the time as well.

 

[green1]

yep

 

[Small Block]

fastback is on it. Do it that way. Do you understand what he said?
Small Block

 

[bargeahead]

fastback is on it. Do it that way. Do you understand what he said?
Small Block

Glad I found this cause " No, I don't". I'll be going 7.25 to 8.75 and figured to shorten driveshaft the difference between axle center to u-joint center of the two. Are you doing the same 1BD71 ?

 

[jamesdart]

probably come out with the same dimension either way or close enough to work, but i always slide the yoke all the way in, pull it out an inch and then take the measurement from center to center. on something like a truck with more of a driveshaft angle it might make a difference.

 

[RedFish]

bargeahead ,
If the only change is the rear end then yaeh that difference in housing is all you need to know. The first post mentioned the 727 trans so it may be replacing a 904 . More difference there.

 

[1BadDodge71]

Ok,well the thing is the yolk on the end of my driveshaft is still for the 904.Will it still slide in?I havent tried yet but I thought the shaft on the 727 was bigger than the 904s shaft.o.0

 

[RedFish]

Ok,well the thing is the yolk on the end of my driveshaft is still for the 904.Will it still slide in?I havent tried yet but I thought the shaft on the 727 was bigger than the 904s shaft.o.0

You'll need a 727 a yoke. Plus a different length tube, You might be better off to buy another drive shaft. Even if you still need a special u-joint at the rear, there's no need in going that route at the front joint also.

 

[65Vart]

Glad I found this cause " No, I don't". I'll be going 7.25 to 8.75 and figured to shorten driveshaft the difference between axle center to u-joint center of the two. Are you doing the same 1BD71 ?

2 1/4 inches Barge and you are good. Just did it (as long as the trnny stays the same).

 

[bargeahead]

bargeahead ,
If the only change is the rear end then yaeh that difference in housing is all you need to know. The first post mentioned the 727 trans so it may be replacing a 904 . More difference there.

2 1/4 inches Barge and you are good. Just did it (as long as the trnny stays the same).

Thank You ! Best of luck 1BadDodge71.

 

[Supershafts]

Whooaaa....

That slip yoke method only works WHEN YOU ARE USING that slip yoke...

If you are having the shaft shortened and you intend on putting the slip yoke on after without it being at the shop i would recommend you send the slip yoke with the shaft, or have them supply the slip yoke for the shaft....
The slip is part of the shaft and should be present when balancing...

If they are supplying the slip yoke, do as you were told...

Measure from the trans seal to center and the output shaft to center (or how much the output shaft is past or before the seal) ...
Which is the FACE of the end yoke on the diff where the strap kit meets the end yoke..


Also i would recommend losing the factory shaft....the factory shafts have dampening tubes inside adding to driveline weight...
In the performance world you do not want that bs in there... nor do you really want the neck down shaft

 

[cjdive]

Fastback is right...I had mine shortened a few years ago when I swaped out a 318 with a 360 and 727.

 

[redfastback]

When I get a trans built, I get a slip yoke from him so I can measure. Then I deliver the slip yoke and the measurements to him to build.

 

[Supershafts]

Fastback is right...I had mine shortened a few years ago when I swaped out a 318 with a 360 and 727.

He is changing his trans also and DOES not have the slip yoke...

RedFB listen to the driveline shop, when he builds it he'll have the slip yoke and make it right.... or when it's wrong, no one here is going to be paying the 2nd time...