[Holeshot71]

I'm getting ready to convert my "71 GTO from a TH400 over to a Muncie 4-speed and have a couple of questions.

I've read that some cranks from cars with automatics may not be fully machined for a pilot bearing. It's unclear if there is a bearing or bushing that will work for this issue with good results or is removing and machining the crank the only "fix".

Also, will the TH400 crosmember and drive shaft work with this conversion? The Muncie that I plan to use is out of a '72 GTO and has uses the same yoke as the TH400.

Thanks!

[Old Man Taylor]

Buy the bearing and try it, chances are that it willl work. If not then you can buy a bushing and have the OD turned to fit. I came up with the dimension for mine by using the straight part of a paper clip and cutting it until it simulated a press fit in the hole. I used this dimension to cut down a bushing. Chances are that the shop will have to make a tool to hold the bushing in order to machine it down.

[4dblnkldude]

Personally I've never seen a poncho crank that did not have a provision for a bearing/bushing. But they are out there, perhaps someone else will chime in. As far as the x member and driveshaft, I dont think the x member will work, but the shaft im fairly sure on. we need a GTO guy!

[Old Man Taylor]

The cross member will work, but you will have to move it about 6" forward. I used the cross member itself as the template. Bolt it to the the trans, make sure everything is lined up and centered, and then mark the frame through the holes in the existing cross member.

B/T/W, I have personally experienced two Pontiac crankshafts that have not been machined for a pilot bearing. One was a '68 400, the other was a '69 428.

[lfdsteve]

To my knowledge, the yoke from the th350 will work on the muncie, not the 400.
Steve

[mrennie]

Around 70 (maybe 71?) Muncies went from 27 spline output (TH350 yoke) to 32 spline output (TH400 yoke).

[Old Man Taylor]

I went brain dead. Since your car could come with either trans from the factory, your frame will already be drilled with the holes that you will need. As for the drive shaft, I think there is about a half inch difference in overall length, so you will have to verify the fit yourself.

[61-63]

I have used a Dremel with a stone to grind out the pilot bearing hole in the rear end of crankshafts. They seem to have bored the hole in steps on some automatic cranks and the last step didn't go deep enough and the Dremel will take care of that.

[Holeshot71]

Thanks for the input. It will be intersting to see what I'll find when I get it apart..

Is the bearing a slip fit into the crankshaft or do you have to tap it in? If I end up going with a bushing should it be the same interference as the bearing or should there be a bit more?

Something else I thought of. The spedometer cable connects on the drivers side on the TH400 and the muncie connects on the passenger side. Is there an extension housing/adapter and cable avaliable or will the entire cable need to be replaced with a longer one??