No sprag linkage, can I still drive in reverse?

[Gunfreak25]

I searched on this some, and the general consensus seems to be that for sprag equipped vehicles the vehicle cannot be driven in reverse if the sprag is still in the "forward position" which is what it stays in due to the spring pressure. This is on my GMC which has a sprag Tcase, but it pertains to the early M35's as well.

The truck has been repowered and with the repower the original transmission shifter and linkage was in no way compatible. The original setup not only shifted the Hydramatic but it also shifted the sprag at the same time (forward, reverse). It was quite a complex series of linkage bits and rods.

My truck of course no longer has the linkage to shift the transfer case (the rod that sticks out the front of the Tcase). So it is therefore always in the "forward" position. Have not driven the truck but 20 feet or so in reverse, and it did just fine with no odd noises to speak of. I was told without shifting the Tcase in reverse, the sprag will simply "slip" and you won't have front axle power whilst in reverse. I was told it was nothing to worry about, but now I am hearing that failure to shift the Tcase into reverse can cause the front axle to snap?

If this is so, I am just going to drop the front prop shaft tomorrow since it will be an asphalt queen anyways.

 

[gringeltaube]

I have never had the chance to look inside one of the GMC T-cases....

Fact is that IF (BIG "IF") your's is a T-136-21 TC with the two sprag clutches AND that forward clutch is still operative... then the truck would drive (or roll) backwards only a few feet until driveline wound up enough to halt the vehicle, eventually causing that feared loud "BANG", or something worse!

In our country many old gasser M35s have seen their engines & transmissions replaced with more modern stuff, but still retaining the original T-cases. Normally what they do is fab some kind of lever/linkage to manually actuate the rear sprag while going in reverse.

G.