TH400 vs. TH350 Driveshaft Question Please

[67mbsc]

Hey Everybody!
I just put a SBC in my 67 using the 6 cylinder mounts, and a TH350 trans that was supposed to be a ""good"" one, but,,,,,,,,yep, it went to lunch before I put it in apparently! So, now I'm supposed to be getting a TH400 for it. What options do I have for the driveshaft/mounting using the 400 in it's place? I'm hoping I don't need to cut the shaft, a good machine shop is not to be had here.
I do have a spare set of V-8 mounts if needed and it's getting rodded so I can put what ever in for a crossmember, that doesn't matter.
Please let me know your thoughts, thanks so much in advance.

[davidh]

I know the splines for the th-350 and th-400 are different on the yokes. Dimensions are differnet too. You will likely be looking for a driveshaft. I Know it's not what you want to here.

[67mbsc]

Thanks. I wanted to hear the truth. Thanks for that. And, after all, if it's for the sake of running a 400, it is worth it IMO.

[special-K]

Rather than cut the driveshaft(if too long),I`d move the engine up to V8 position.

[67mbsc]

Special K, that's one thing that I just wasn't sure about, whether or not that could make up the difference. Is a 400 1 inch longer,(using short shafts on 350 & 400)? Thanks

[hotrodmtodd]

Just measured 1 of each. Both 28 1/2" case length for short shaft. I have dimensions on more trannies if you need them. Do you have a slip yoke or a carrier bearing? Lots of stuff to consider. If you like to weld, you will be fine. You are in the right place for info. I'm not even a pimple on the butt of some of these guys. Take care, Hot Rod

[69 longhorn]

Go to www.tciauto for trans dimentions. You will find that the 400t is 11/16 " longer than the 350t (both shorttails) , & does have a different slipyolk. As far as the trans crossmember, the same one under the 350t willwork ,but you may need to slot the holes in the center for minor adjustment . you will no doubt need to cut & balance the shaft, 7 dont bother moving the eng foward to correct the shaft lenght problem.....it will make the problem worse. its a 3 1/2" move to factory v8 sb spot. Good luck,crazyL

[davidh]

Back in 67 and 68 if you got a truck automatic, if you didn't get the powerglide you got the th400. YOu might get lucky and find one of these trucks and get what you need. Remeber the turbo 400 takes more HP to move than the th-350.

[gangforward]

Just did this on my 67 Long Bed. Converted from a glide to TH400. I found a 3/4 ton driveshaft (TH400) and simply moved the engine mounts forward.

I did have to replace the front yoke (there are two sizes of TH400 Yokes!) one I needed miked out at 1.885. Got that from Hughes. The other trick is to get a 3130/3150 ujoint to mount it to the rear end. The shafts on the ujoints are bigger than the rearend. Again got the special ujoint from Hughes.

No welding, no cutting, bolted right in. I also replaced the other two ujoints, so the driveshaft is as good as new. Works great, and is much stronger.

[Johns70]

yeah there is two different yokes for the th-400, one is small for the cars and 67-68 1/2 ton trucks with a 1310 u-joint and the other is the large that came in the trucks 69 and later? but it has the 1350 u-joint. the diameter is different to like gangforward said.

[67mbsc]

Sounds like to me that my best bet will be to leave the engine in the 6 cyl slot, and cut the driveshaft. I DO have a carrier bearing, so I'll cut the back shaft, right?
Thanks so much guys, I REALLY appreciate the tips.

[69 longhorn]

Originally Posted by 67mbsc

Sounds like to me that my best bet will be to leave the engine in the 6 cyl slot, and cut the driveshaft. I DO have a carrier bearing, so I'll cut the back shaft, right?
Thanks so much guys, I REALLY appreciate the tips.

No sir, you need to cut the front shaft! After you cut, both pcs need to be balanced as an assy. best of luck, crazyL