[pontorquer]

Can someone please tell me the length of the Turbo 400 drive shaft for the 1974 Firebird I need the lenght from end of yoke to the other end of drive shaft so the full length measurement ? Thanks

[Skip Fix]

It will all depend on your yokes. My factory 78 TH 350 is 48.5 .
My Camaro with a TH400 and a MW shaft with it and their yoke and the 12 bolt is the same length! The other yoke I first measured with was not as deep.

[JLMounce]

I believe it "should" be 48" for an automatic equipped car.

That said, I highly recommend actually taking this measurement yourself. Unless you can 100% verify that nothing has changed down there as far as transmission, rear-end etc, simply ordering up a driveshaft length like that can easily net you a too short or too long situation.

You want to get the car up in the air on it's suspension, so it's loaded at ride height. If you're having a shaft built locally, most places will give you the yoke you want to use to go fit it and get the measurement. Push the yoke in the trans, then pull it out right at about an inch. Measure from the distance from the trans yoke to the pinion yoke and give that measurement to the people building your shaft.

This is a good time to give those same people some idea about how the car will be used, what kind of power it's making, what types of RPM's it will see etc. There's a ton of video out there of people running around with crappy drive-shafts. the end results don't look fun.

[68azbird]

you got a tape?

[Big Bear]

Hi Pascal Measured the 74 shaft and it's 48" centre to center of the caps. Is the 455 going to be installed soon? Barry

[pontorquer]

Thanks guys, I was just looking for stock yoke/driveshaft length, I do have the 48" driveshaft. Just hoping my yoke is correct length, I need to know if this will work with my original 10 bolt or a 1970 FB 12 bolt rearends same ... The build is slowly going

[JLMounce]

Not apples to apples, but teh Moser 12 bolt I installed in my 69 Bird, shortened the total driveshaft length by about an inch to inch and a half.

If you have the stock trans, in the stock location and the stock 10 bolt, you're probably good. If you install the 12 bolt I would bet on the driveshaft being too long.

[tooski]

Swapped a TH350 for a TH400 in my 75 FB. Expected to require a new driveshaft. Put the TH400 yoke on the ds. Perfect fit.

[Gach]

This is what you do, to fine Drive shaft length, stick the yoke ( if you have a spare one ) if not use your existing drive shaft and let it lay down. Stick yoke all way in, then pull it out 1” from there take a measurement from center of yoke, to center of the rear. If need be put a center line on the yoke.

Going blank for some reason on what its called that connects drive shaft to yoke.
But that center.

Reason for pulling it out 1” before measurement is so driveshaft can easily be installed and pop into the rear. Once you have that measurement just Measure the driveshaft you have. Believe its call universal joint

[pontorquer]

Ok Thanks again, Tooski you must have found a short TH400 yoke (how long) ? The TH350 Xsmn is shorter than the TH400 ...

[Big Bear]

74 yoke is 5.250" long from end to center of cup. Measured the 70 TA with 12 bolt, it's 48" long. Same as the 10 bolt.

[Skip Fix]

What I found on my MW vs a generic TH400 yoke was eventhough overall length was the same the depth it can go before hitting the output shaft was different.

[tooski]

Originally Posted by pontorquer

Ok Thanks again, Tooski you must have found a short TH400 yoke (how long) ? The TH350 Xsmn is shorter than the TH400 ...

The overall length of the short tailshaft TH400 is 29". The overall length of a short tailshaft TH350 is 27 5/8".
I had pics of the difference in the yokes, but I can't find them.
The two yokes had the same length splined sections. The 400 yoke looked like the one in Gach's pic. The 350 yoke had a stepped section between the 'U' and the splined section. This stepped section is 1 3/8" long - the diff between the trans. I did have to move the crossmember back.

[tooski]

First one is a 350, then a 400 yoke. Very similar to the ones I have/had.

[Held for Ransom]

I'll add my 2 cents.
Driveshaft - 48" center of U-joint hole (1.055" approx.) to center of U-joint hole. 49" overall length. 2-3/4" outside diameter.
Front yoke - 5.25" end of yoke to center of U-joint hole. 6" overall length. 4.125" bottomed out inside to outer edge. Full length inner splines.
Overall assembled length - 53-7/8". Outer U-joint clips.

[pontorquer]

You guys rock ! Can't ask any better with all these measurements, I'll measure my yoke added to my 48" driveshaft and let you know the overall length , I think It will be right ... Indeed, same lengths HFR gave me Story is the driveshaft was given to me from a buddy who said it came from a mid 70s Camaro with a turbo 400 and I got the yoke at a swapmeet ...

[Skip Fix]

https://www.markwilliams.com/driveshaft-measuring.html

The depth of your yoke is a big factor. I had a stock TH400 yoke on a stock 48.5 length driveshaft and it would NOT fit with my 12 bolt and TH400. My MW with tehir deeper yoke was 48.5 and fit perfect. Theirs slid the U joint holes further in the trans.