Modifying a Transmission Tunnel for 4 speed Conversion (1 Viewer)

[DesertFJ40]

Hi all,

I have a 1971, originally a 3 speed column shift fj40. I would like some insight on how to approach the issue that deals with a 3 speed to 4 speed transmission conversion. The early 3 speed tunnel that I salvaged does not fit and will not snug down over the newly placed 4 speed.

For starters, I have a T-case saver that does kinda block the 3 speed cover from fitting as it should. But besides that, even if it wasn't hitting, there would only be about 1mm clearance from the 3 speed cover to the transmission. And to me, that's sitting too close and would like some more clearance. I went ahead and purchased a Chinese top cover from topnault for a 4 speed transmission. However, as some of you might know, that style cover is longer on the rear and the holes on it are different. So to make that fit, I would need to cut down the length and do something about the holes so they can line up correctly.

For those of you that have modified an early 3 speed cover to fit on a 4 speed transmission , what did you do? I know there will need to be cutting and welding to make the 3 speed cover taller, just wondering where to make the cuts and how much work will it require to do.....and also, those who were able to use a 4 speed cover, how did you make it fit on the early style fj40s?

The top cover on the left is the new chinese cover for a 4 speed. the one on the right is for a 3 speed transmission. while similar, they fit different and not 100% a direct bolt on in my situation.

 

[charliemeyer007]

Glue some 3/4 wide 1/4 thick plastic/wood strips to the bottom of the 3 speeds tunnel to shim it up a little. Then figure out what gasket to make the front firewall side to fit. When you figure it out, replace the wood or plastic with like some aluminum flat stock.

Or perhaps make the motor/T/T sit a little lower in the back

 

[SteveH]

I did a 1" cab lift on an FJ45 to get the 4 speed trans to clear the 3 speed cover. Harder to do on an FJ40, but there are fitment issues, for sure. In my case, the cab lift made the cab line up properly with the bed (for some reason) so it didn't look dorky when I was done with it.

 

[Living in the Past]

I did this conversion over thirty years ago. I did not cut the frame or tub to did it. I Shimmed the front motor mount with a couple of larger fender washers. I ran a stock tunnel cover for a short while. I used either a 75 or 76 tunnel cover. Cut the back off the match the length of the pre 9/72 cover. I formed the right side of the cover to match the tub floor. All the holes at the front of the cover matched the ones from the earlier cover. As I remember the left side matches as well. Used some thick weatherstripping across the back because the cover was taller than the original cover at that location. I was able to use the stick shift boots for a four speed.

I'm the picture above can see the bump for the vacuum shifter is just longer than the three speed and extends further back. This was because Toyota used a three speed transmission up to 10/82 in some markets.