Transmission crossmember for 700R4 swap into an 82?

[Galane]

Pulled the old engine and trans out of the 82 GMC today. Found it's a Hecho en Mexico casting 10066036. Might be a 4 bolt, might not. Not pulling the pan to find out.

Did some measuring on the dud 3-speed VS the rebuilt 700R4 and found that the mount holes for the 4-speed need to be farther forward because they are on the case instead of on the tailhousing on the 3-speed.

What years of truck should I look at in the yards for a crossmember that will bolt in and fit up to this transmission?

Another difference is the old trans has the fixed output yoke while the one going in has the sliding yoke. Have to have the front section of the two piece shaft modified anyway.

 

[bluex]

Just use the cross member you have. Move it forward an drill new holes. I actually had to move mine back for my 700r4 though....

 

[Galane]

No dice on using the original crossmember. It's top side is up too high. The 3 speed's mount was on the tailhousing.

The 700R4 mount is on the case, right behind the pan. There are holes in the frame for three different locations for the crossmember.

The original one is raised up in the middle with an upward curve at each side for exhaust pipe clearance.

What I need is most likely like the one in this thread. http://67-72chevytrucks.com/vboard/showthread.php?t=178731 Very convenient how the person who posted that didn't mention what year/model it came from.

 

[scottybaccus]

If you install your cross-member where it was, and place a straight edge across the bottom side of the frame, the pad for the mount should be about two inches above your straight edge. Take the cross-member out and position the trans where you get 3 to 6 degrees nose up on the engine oil pan rail. You should find that the bottom of the rubber mount is about two inches above the straightedge across the bottom of the frame. Don't be fooled by the curves in your cross-member. It dipped down, and back up to clear a single exhaust with a catalytic converter. Also, make sure you are using the right mount. They are different. You also want a single stud on the bottom side. That should be what you had. Aftermarket urethane mounts, and some rubber, for the 700r4 may have 3 threaded holes on the bottom for multiple applications.

If you don't find it fitting as I say, set the drive line angle in that 3-6 degree range, and send me some pics with measurements from the straightedge. I offer a custom dual exhaust cross-member that interchanges with the one in the thread you shared. It's $200, shipped, with hardware. If you do have a funny scenario, I'd like to see it so I can look at making a solution. Have a look at my shop page through the link in my signature.

 

[Galane]

Don't be fooled by the curves in your cross-member. It dipped down, and back up to clear a single exhaust with a catalytic converter.

Nope, it didn't. It's a 1982 one ton that had a TH400. The crossmember for that transmission lifts quite a ways above the bottom of the frame and has an arch at each end for dual exhaust. The two ends that rest on top of the bottom of the frame are the lowest points. Has to go that high due to the TH400's mount location on the tail housing.

You are thinking of the later style crossmember that went down, under and up the outside of the left frame rail, for TH350 or 700R4/4L60/4L60E. I could have used one of those, but I don't like drilling holes in frames. Too much work. Or perhaps the longer one used on the 1988+ standard cab and 1991+ crew cab, Jimmy and Suburban.

Jacking the cab up a bit just to be able to get the upper angle bracket bolts out of their holes is going to be a PITA. Probably will find those four cab mount bolts are halfway rusted through like the two bolts holding the radiator support to the frame. At least circa 1980 GM quit riveting the auto trans crossmembers to the frame!

I went to CBASS today and after walking over the whole yard finally found one out of a truck that had a TH350. It's almost flat but still has slight arches at each end to clear dual exhaust. It also has the angle brackets at each end, like the "wraparound" one has only on the right.

The angle brackets are longer than on the TH400 crossmember.

The frame has three locations to bolt the crossmember in and since the 700R4 was an option in 1982 I bet I'll have no problem just putting this into the middle set of holes.

The only gotcha on the one I got was it was removed by "TJ" and his go-to tool, a Sawzall. All the few other crossmembers of this type he'd made two cuts and presumably the centers left with the transmissions. He'd even chop the easier to remove wraparound ones. On this one he only made one cut so I got it welded back together by a guy who is really good at this type of welding. It's what he does for a living.

"TJ" doesn't work at CBASS now, he was chopping up too many good parts with his happy Sawzall.

I also snagged a nice GMC grille of the same style but in much better condition, with the "chrome" facing instead of all silver painted. $30. Chopped crossmember was free but the angle brackets will cost a few $ once they get them off the truck.