razorback

ok, is it bad to have a shorter driveshaft than the stock one? my driveshaft (overall front diff to end of ujoint holder, minus yoke) will be someting like 26-28 inches. is this bad? could any problems be caused from this?

Falcoms

yes, becasue if you use a longer front slip joint to go over the splines into the trans, it acts as more of a lever arm on the ujoints (like putting a pipe on a ratchet for more torque), puting more force on them and causing them to break from stress due to mount flex (chassis flex if solid mounts).

Crash Test Joey

iTrader: (1)

It depends on what the question really means. If a stock driveshaft would be six inches too long to actually fit on the car, you really don't have a choice but to shorten it. Driveshaft length is determined by measuring the tailhousing and tailshaft of the transmission in relation to the rear differential. Moving the transmission would only be done if you can't maintain the correct u-joint angles with where it's mounted already. And then you would only move it up or down - or if you were building a very long vehicle you'd want to use two driveshafts joined by a CV joint in the center.


Using a shorter driveshaft will have the opposite effect of what you're describing.

The shorter the driveshaft (assuming the proper angles are still maintained and the depth of engagement of the yoke on the splines remains the same) the less likely you are to break the driveshaft or anything else.

Unless I'm mistaken he was referring to the fact that the transmission will be further back in the car than the stock one. It makes sense because my driveshaft is about 28.5 inches long too. It would make no sense at all to use a shorter shaft just to use a longer yoke (unless it was the wrong yoke in the first place).

razorback

i mean that i would have a custom shaft made, they sell one without an end welded, you make it to the length you want, weld it up, balange it, and bolt it in. it would be shorter than the length. and go to match whichever driveshaft i would use would be to the correct length. now i was just asking if there is such a thing as a driveshaft that was too short, like if it would still reach the trans, and rear end, just be shorter than the stock length (stock rx7 length) and i was reffering to the trans tailshaft going back into the trans tunnel more so that would make it the driveshaft shorter. ill post photos if im not explaining it properly.

Crash Test Joey

iTrader: (1)

Easiest thing to do is install the motor and trans, and measure for the right length driveshaft. You can get a new one custom built, or what I did was have the stock F-body driveshaft shortened - the front already fits the trans, the rear they just cut and welded a yoke to fit the RX7 rear.

http://www.a1driveshaft.com/driveshaftFrameSet1.html

That's who I use (they have 2 locations near me so I just went in and talked to them). Or another popular shop is www.dennysdriveshaft.com