calculating driveshaft length
calculating driveshaft length Ok so im putting a th400 w/ 9'' tailshaft in w/ a stock rear end.
now stock driveshaft length is 40.5''
4l60e length is about 31''
th400 length is about 34''
from the stock dimensions that equals 71.5''
31+40.5=71.5
now for the th400 couldnt i just use
34+X=71.5 which is of course 37.5''
now going off that how accurate is that? I dont really feel like putting the th400 up in there just to figure out what I already can figure out on paper.
What sizes DS have you ordered for a th400 swap with stock rear end? should I just get one 2'' shorter?
now stock driveshaft length is 40.5''
4l60e length is about 31''
th400 length is about 34''
from the stock dimensions that equals 71.5''
31+40.5=71.5
now for the th400 couldnt i just use
34+X=71.5 which is of course 37.5''
now going off that how accurate is that? I dont really feel like putting the th400 up in there just to figure out what I already can figure out on paper.
What sizes DS have you ordered for a th400 swap with stock rear end? should I just get one 2'' shorter?
Staging Lane
Joined: Apr 2005
Posts: 92
Likes: 0
From: Westminster, MD
Only one true and accurate way and that's to measure IMO.
Put the car on stands with weight on the axle to set it at ride height. Put a slip yoke in the trans output shaft. Bottom the slip hoke, then pull it out 1". Now measure from the slip yoke U-joint centerline to the rear pinion yoke centerline.
Denny's has another method which is equally accurate, but the trans has to be in the car and still measure with all components installed and at ride height.
Put the car on stands with weight on the axle to set it at ride height. Put a slip yoke in the trans output shaft. Bottom the slip hoke, then pull it out 1". Now measure from the slip yoke U-joint centerline to the rear pinion yoke centerline.
Denny's has another method which is equally accurate, but the trans has to be in the car and still measure with all components installed and at ride height.
You need to measure from the end of the tailshaft housing to the end of the pinion yoke.. If you not meassured correctly you can cause damage to the tailshaft bushing and will vibrate like crazy if it's to short.
ok for the people that said measure it....
I DID and what did i find, the same exact thing I did on paper
from the end of the tailshaft to the inside of the u joint cup (slightly different from the measuments above) it was 42.5''
so then I measured the stock one in the same manner and low and behold its 2'' longer! 44.5'' who would have guessed?
I DID and what did i find, the same exact thing I did on paper
from the end of the tailshaft to the inside of the u joint cup (slightly different from the measuments above) it was 42.5''
so then I measured the stock one in the same manner and low and behold its 2'' longer! 44.5'' who would have guessed?
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Originally Posted by WE TODD DID
Contact whomever is going to be building the drive shaft. And measure it with the car at ride height. No sense in you getting a bunch of mixed up opinions.
i did....see above...
does the factory measure every car? NO
the only change would be the tranny, which grew 2''. Thus making the DS needing to be 2'' shorter! My on paper calcs. and actual measurements show the same results!
I dont understand why everyone says measure measure measure omg measure. Putting in a th400 does not call for a "custom" DS. It calls for a premade DS spec'ed to fbodys.
the only change would be the tranny, which grew 2''. Thus making the DS needing to be 2'' shorter! My on paper calcs. and actual measurements show the same results!
I dont understand why everyone says measure measure measure omg measure. Putting in a th400 does not call for a "custom" DS. It calls for a premade DS spec'ed to fbodys.
Different brand yokes stick out of the trans at different lengths (sometimes over an 1" difference), so the only accurate way is to install the yoke & measure, or to buy a complete drive shaft including the yoke & provide them with a measurement. This measurement is from the rear seal & from the end of tail shaft to the rear end yoke.
Dennys, Inland Empire & many others insist on the measurements because different rear ends, lower control arms & rear yokes and tail shaft types (slip vs bolt on) add up to quite a bit of length difference. If they provide an off the shelf shaft that does not fit, they eat it. When you measure wrong, it is your problem.
Dennys, Inland Empire & many others insist on the measurements because different rear ends, lower control arms & rear yokes and tail shaft types (slip vs bolt on) add up to quite a bit of length difference. If they provide an off the shelf shaft that does not fit, they eat it. When you measure wrong, it is your problem.
Last edited by Lonnies Performance; Sep 12, 2007 at 08:55 PM.
Originally Posted by dlove
does the factory measure every car? NO
the only change would be the tranny, which grew 2''. Thus making the DS needing to be 2'' shorter! My on paper calcs. and actual measurements show the same results!
.
the only change would be the tranny, which grew 2''. Thus making the DS needing to be 2'' shorter! My on paper calcs. and actual measurements show the same results!
.
The factory doesn't use adjustable suspension peices either. Mine was over 1" longer than my buddies with the same setup because our suspension was adjusted differently. I am not saying that was going to be the case on your car but something to be aware of before having to buy two driveshafts when if you took the time to measure you could have bought one.
Teching In
Joined: Jul 2007
Posts: 27
Likes: 0
Measuring is the only way to go. I made the mistake of measuring the yoke to yoke distance (bottom out the tailshaft yoke, pull out 1",..). What I didn't take into account was that the new DShaft would have 1350's on both ends. The new yoke had different dimensions. The new DShaft is slightly short. I get a vibration at 70+ that is terrible. When the driveshaft is installed at ride height with the suspension loaded I get side to side play at the tailshaft end. If I push it in another 1/2 inch, no play. I'm going to talk to the builder about lengthening. I have 1.125" exposed when mounted.
