I'm converting a straight six saginaw 3-speed car to a big block TH400 car. The crossmember holes are farther apart on the manual crossmember than the automatic piece. Do you use one of the existing holes for reference for the TH400 crossmember and drill the other hole, and if so which hole do you use?

I have the subframe out of the car and would like to be able to install it before putting it back in and trying to figure this out.:(

Thanks,
Casey

I'm converting a straight six saginaw 3-speed car to a big block TH400 car. The crossmember holes are farther apart on the manual crossmember than the automatic piece. Do you use one of the existing holes for reference for the TH400 crossmember and drill the other hole, and if so which hole do you use?

I have the subframe out of the car and would like to be able to install it before putting it back in and trying to figure this out.:(

Thanks,
Casey

The holes in the sub frame are the same for any of the transmisions cross members as I know it. The shape of the cross members differ from the transminssion line. For the TH400, the cross member is very different. It so sort "bowed" in the rear than has a approx. 2 inch piece weld to the rear of it for the transmission mount.

Here is a pic of Muncie my old Muncie trans mount -
http://img.photobucket.com/albums/v206/error3b/camaro_pics/100_2617.jpg

Here is the TH400 Cross Member looks like -
http://www.ss396.com/mm5/merchant.mvc?Screen=PROD&Store_Code=camaro6769&Product_Code=FCM-85

I bought a crossmember from Rick's First Gen that looks exactly like the one in the picture of the link, but the holes are no match. I assumed all the mounting holes would be the same like you said. The assembly manual is not very clear on this either.

The BB turbo400 crossmember is tubular (totally) steel with a tab welded on for the tranny mount. Pictured is the powerglide/t350/manual crossmember for sb cars which is a box section construction.

The mount holes should all be the same. The BB frame stands move the engine approx 1" to the left, the t400 crossmember is also 1" left, the sb crossmember is centered.

Is this where the holes don't match?

Here ya go. Original. The mount, not the overdrive.
http://epitomesrebuild.com/images/173.JPG

The holes that I'm refering to are the ones on the subframe. I changed the frame mounts to the 69 BB mounts for the extra water pump clearance. The tubular crossmember may be the way to go for me. I'll check into it. Thanks everyone for the help.

I was informed that you must mount the motor and trans, then attach the crossmember to the transmission to accurately mount the crossmember, then drill holes. I was looking for a quick and easy way to do this, but this is it.

OK, the holes where the crossmember mounts to the subframe. Not sure what yr subframe, but you shouldn't need to drill new holes. On my 69 I went from powerglide to t400 and it was a bolt in.

Are the holes not lining up front to back, or side to side, I thought the subframe had multiple holes for just this kinda thing, but I may be wrong.

Maybe it's the engine mount towers. If you used the s/b ones, I think it locates the engine too far back in the bay, and thus causing the transmission to be too far aft to align with the crossmember. Also, I think the driveshaft is the same for the TH400. (I know it's the same for all other engine/tranny combos, but not positive for TH400.) If the tranny is too far aft, you'll have to have the driveshaft cut down.

Also note that the towers are different for 67/68 and 69. I don't exactly know the differences, but they do not enterchange.
There may be other alignment issues, too

The holes on the subframe (front to rear) are farther apart than on the TH400 crossmember. The other crossmember fits: powerglide, TH350, and all manuals offered at the time. This is on a 67 subframe. I'm not sure if 69 would be different. The hole spacing on the subframe is approximately 3 1/8" apart and crossmember is 2 3/8".

Something's skweewy.