Transmission cross member issue (Help!)

[tranz am]

I am about to convert my 69 gmc from the original 307 & 3 speed to a 350 & a 4 speed m21. I see that there is no cross member under the 3 speed and that it attaches to mounts at the bell housing. The unit I want to install doesnt have the provisions for this mount set up on the bell housing. I want to use the large bell housing that accommodates my 11 inch flywheel. will the stock bell housing accommodate the 11 inch fly and will the M21 work with it? Also can I find a cross member to use with my M21. Will one from a th350 work? Thanks

[bandit1]

my stock 307 and 3 on the tree is running an 11 inch clutch. I would run a rear crossmember though.

Jared

[glock35ipsc]

I would think the auto x-member would work fine. Should even work in the original auto x-member location.

[Tx Firefighter]

Reuse the original bellhousing with the new engine, larger clutch and the 4 speed. Then you don't have to mess with swapping the crossmember.

[Spray-Bomb]

I don't know if it'd work for your 4-speed, but I built my own X-member for my truck out of some C-channel & angle iron

[airdale94]

The Muncie & B/W 4 Speeds use the same cross member as the TH350. A TH400 would require some modification.

The length from bell housing to mount are the same as is the rubber mount.

[Tx Firefighter]

Airdale, on these trucks, the original standard transmissions used a bellhousing with mounts built into the bottom of it. The trans did not use a crossmember at all. This is true of the original standard trans in these trucks, including the Saginaw 3 speed and Muncie SM460 and SM465 four speeds. There were no Borg Warner 4 speeds originally on these trucks.

[airdale94]

Yes, I mean't the Muncie and Borg/Warner car transmissions. He said he was gonna put a M21 in it.

I used to be a 70-81 Trans Am man and the T/A's with TH350's or manual transmission Muncie or B/W use the same trans. cross member. If you had a TH400 and wanted to swap to a manual you needed the TH350/manual crossmember.

So what he could do is get I guess a 67-72 truck TH350 cross member. Not a TH400 though.
I would use your large bell housing. Not the stock.

T FF: I read in one of your posts you were an a/c mechanic. Was it in the Nav? That's what I did. Wasn't actually an airdale, but I like the nic and I did work topside.

[tranz am]

Cool this is all great information. I thought that the cross members were the same just as in the T/A's. Actually the engine trans combo is still sitting in my T/A which is being restored. I cant stand 350 horses just sitting around like this!
The truck really needs it any how considering the three speed granny sucks in a performance standpoint. I almost think that using all the mounts possible would be the best way to go, more support I would think?

[Tx Firefighter]

Airdale, I was always a civilian A&P. I did corporate jets, a little helicopter stuff, then I built ME-262's for museum dispaly.