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  • 1965 - 1973 Classic Mustangs -General/Talk-
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Driveshaft length... how do you know if it needs to be shortened?

  • Thread starter Thread starter SadbutTrue
  • Start date Start date May 21, 2008

SadbutTrue

Founding Member
May 1, 2002
2,390
4
49
Granada Hills, California
May 21, 2008
#1
  • May 21, 2008
  • #1
(I tried these follow up questions in my last driveshaft thread but it fell by the wayside after I tried to bump it, so here goes part 2)

I swapped a C4 to a T5 last summer. Used the NPD swap yoke and didn't shorten the driveshaft. Its been like that for about a year, roughly 2,000 miles (max).

There have been no problems except that my rear main seal is leaking (it was a used transmission to start with, so I'm not sure if the driveshaft length had anything to do with it).

Questions:
1) If the driveshaft has been in that long without any issues, my gut says getting it shortened is a waste of time and money. Is my gut right?

2) Could a slightly too-long driveshaft cause a rear main seal to leak? My gut says that if the driveshaft is too long, you'd have a much more obvious issue than a leaky rear seal.

On a semi-related note... does anyone know a good place to get a 1989 World Class T5 rear main seal?

Thanks!
 

Tim65GT

Active Member
Feb 24, 2004
1,149
2
39
West Texas
May 21, 2008
#2
  • May 21, 2008
  • #2
When I swapped in my AOD I was able to install the driveshaft without shortening it. I took it for just a short drive (about a half a block) and when I did a U-turn, there was a definite banging noise that i noticed when i got on it a little. So I took it out and had it shortened. I was told by a driveshaft shop to have between 3/4 and 1" of additional slip into the yolk. In other words, if you unbolt the u-joint from the axle flange and slid the driveshaft forward, it should go about an inch before bottoming into the tailshaft.
 

RogerC62

Founding Member
Feb 2, 2000
833
11
38
Dayton, Ohio
May 22, 2008
#3
  • May 22, 2008
  • #3
I was told by a driveshaft shop to have between 3/4 and 1" of additional slip into the yolk. In other words, if you unbolt the u-joint from the axle flange and slid the driveshaft forward, it should go about an inch before bottoming into the tailshaft.
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