6 speed manual transmissions

Found the drawing for the crossmember:



I made it using 1"x3" rectangular tubing, cut, welded and reinforced at the joints and the mounting points and with a 3 1/4" wide x 14 gauge thk. flange welded on the bottom. Could make something simpler from formed tubing or reinforced heavy plate or just modify the stock crossmember like in needafasterAMX’s post.

The stock crossmember interfered with my header pipes and X-pipe, so made something completely new to clear. It was made to be flush to the floor pans for max exhaust clearance, but seems to transmit a bit more vibration into the cabin. May try bolting to the floor pans with thin rubber between. The urethane transmission mount likely also transmits more vibration as it’s quite a bit stiffer than the stock AMC rubber mount.

For mounting holes, I slotted the holes for the transmission to give a bit of fore-aft adjustment and marked and drilled the holes to mount to the frame rails after installing the transmission. Used a shim to adjust the transmission height to get the angle I wanted. There are a bunch of holes in the frame rails and the rear holes worked well (had to clean the undercoating off and chase the threads).

Note regular T56s have slightly different crossmember mounting points, so will need to make to suit if you go with something other than an LS Magnum. Also, if you use a shallow stock bell or Lakewood 15411 or QuickTime RM8075 with T56 adapter plate, the transmission mount will move rearward.

Edit: I ended up using almost 1/2" thick spacer between the crossmember and transmission mount, so the centre could be made a bit shallower than shown above and use less shim.

Hope this helps.

Edited by Red Devil - Oct/30/2017 at 7:59am

Well I haven't bought anything yet, I'm still contemplating how nice it would be to have a modern six speed in the car. Mostly I wanted to bring this post back up to the front page so I didn't forget about it.

RedDevil and I talked alot in the past....he might have pictures of my Richmond ROD six speed install.  I bought one when they were available, AMC input shaft, Lakewood scattershield.  Custom built trans crossmember, but a slightly modified stocker is probably a viable alternative.  My exhaust system created more issues than the trans.

klvn8r

Hi klvn8r: Sorry don't have photos of your ROD install, but IIRC, it fit pretty easy - just some trimming for the shifter and a bit of the crossmember at the tail. Likely the new short bell with a GM style would gain a bit more room, so even easier to fit.

Hi Armand: Sorry, scrambled photos and lost links. Now updated.

Thanks,RD.

Hi Armand,

I've got the Street Twin w/ Borg&Beck Long PP ... which is their hybrid Borg&Beck w/ Long-style levers. It's heavier than a diaphragm clutch, but been so long since I've driven a stick tough for me to judge.

I only bought the Street Twin because it was on sale as an overstock item and included the flywheel, so cost was in the same ballpark as just a flywheel + regular clutch kit ... and had plans for more power (plans change as you get older).   With the aluminum flywheel it revs very quickly, but it's really a bit much clutch and not enough rear gear, so takes a bit of feathering to slip it to get going. Still not sure if I'm going to fit a smaller cam or more gear (wanted to try it out with the 3.15s to get an idea on gear). Just need to get some real miles on it before can say too much, so have to wait for spring.

Thanks,RD.