Drive shaft length (what's too short?)

[Speedwaypj]

I have a question about the drive shaft length. Let me give you some detail:

1. Running a 429 (Stroked to 460)
2. I have a BW T10B-1 trany with a T10B-7 (long) tailshaft (I believe this came from a 61 - 63 Ford or Mercury).
3. I'm running a ford 9" (WAR pumpkin); ordered 3.25:1 gears.

I don't have the engine installed yet, but I know approximately where it will mount. When I look at the dimensions for the tranny length and Rear end placement it looks like I will ony have 9 - 10 inches between the end of the transmission (shaft) and the (U-joint) center line of the rear yoke not counting the yoke for the tranny which I expect to be at least 3 - 4 inches from the tailshaft to the center line of the forward U-joing.

That gives about 5 - 6 inches for the driveshaft (Tube only) length. That sounds too short to me. I'd like to run the T-10 (it does have the longer tailshaft) if possible but is 5 - 6 inches long enough for the drive shaft tube? If that is too short then I guess I'll have to find a different tranny.

ANy info will be helpful.
Thanks,
PJ

[WardL]

First off, I am not experienced with the technicals of drive shafts, but why are you worried it is too short? Too short for what? My ignorant assumption is the drive shaft is just a way to transfer the engine/trans spin to the rear differential. What makes you think it has to be longer? Long enough to do what? What makes you think you even need a drive shaft? If your set up called for something just long enough to have the universal joints? Like someone said, my 2 cents...

[Dirty Harry]

As I recall, the Cheetah didn't even use a driveshaft, but rather had the output shaft connected directly to the differential, using just one U-joint.

[Rick Parker]

I'd be worried about when you'll be replacing the transmission. I doubt it has the torque capacity to match that engine.

[COBRANIP]

Are you running a live rear axle or I.R.S.?

[Speedwaypj]

Thanks for the responses;
WardL - "What makes you think you even need a drive shaft?" - the rear suspension will move up and down with changes in road, bumps, acceleration, etc - the engine and tranny are fixed to the frame, so there needs to be a way to allow the rearend movement.

Rick Parker - I"I doubt it has the torque capacity to match that engine..." - back in the day I ran this behind a 352 in a 55'Ford for a few years.... Granted this is a 460, has there been problems with the T10 holding up with a big block? What is an alternative?
.
COBRANIP - I'm running a regular Ford 9" rear end (Tru-Trac)
- I believe that with a short shaft the angle of the rearend to the tranny will be quite a bit different while operating because its so close.
Thx PJ

[Grubby]

I suspect it is too short to allow much rear suspension travel. You will have to mock it up or lay it out in AutoCAD and look at how much angle is put on the U-joints at the limits of suspension travel.

Since you have most components in place, I would mock it up and measure the expected angles. Then you can make an informed decision.

Dana recomends max 3 degrees working angle for the U-joints.

John

[Speedwaypj]

Grubby - thanks. I only have the rear end mounted, but from the instruction manual the engine should mount within about a 4 inch area - so I have a good estimate where the engine mounts go. I just didn't want to keep going with the T10 mock-up (need to rebuild the T10 also). There is a good explanation of pinion angle on the following site How to Set Pinion Angles - BumpWiki
Thx...pj

[Jerry Clayton]

Try to make the drive shaft at least as long as the lower control arms--it will be nec essary to limit suspension travel to the range that you can control rear axle housing angle change so as to stay within a +3-3 degree u joint angle with the transmission mainshaft.

[sspano01]

Hi

I have a 429/460 style block and a t56 transmission. My driveshaft overall length was abut 12-13 inches, probably on the order of 5-6 inch tube. Dennys driveshaft made it - they said it was short, but it works.

On the suspension travel, yep that is an issue. I run the shocks in full dampen to lessen the travel. My pinion angle is not quite right, but the shaft needs to be angled so the suspension can travel. So it can be done,must don't get too hung up on driveshaft angles

[Speedwaypj]

Thanks for the info - from everyone's comments,I don't think the BW T10 is a good choice, I'll probably need something stronger.... so maybe a shorter tranny is the best deal - no issue with driveshaft length.
sspano01 - did you have your cobra painted or is that the gel-coat? Very nice!
PJ

[sspano01]

Thank you!
My cobra is the "zat blue" gel coat.
My neighbor wetsanded it, put the white stripes, cleared and polished it.
i put it on the road in May - and it has been terrific!

im working on 66 mustang as well now for a little winter project. that one, I just repainted myself.