The setup: 93 4.3 TBI, 4l60e, Toy tcase - 4.7:1, VSS mounted on the tcase output shaft. All GM components including ECM came from a 2 wheel drive van.

The problem: In low range, it doesn't want to shift out of first gear. If I move the shifter into second, it will shift into second, but if I shift into third or fourth, it won't shift up. When I back off the gas it will drop back into first. This is only in low range. In high range it shifts great.

One thought is that the VSS on the tcase output makes it think it's moving too slow to shift up. Any other ideas?? Any solutions or suggestions?? Any help woud be appreciated.

Thanks!

The setup: 93 4.3 TBI, 4l60e, Toy tcase - 4.7:1, VSS mounted on the tcase output shaft. All GM components including ECM came from a 2 wheel drive van.

The problem: In low range, it doesn't want to shift out of first gear. If I move the shifter into second, it will shift into second, but if I shift into third or fourth, it won't shift up. When I back off the gas it will drop back into first. This is only in low range. In high range it shifts great.

One thought is that the VSS on the tcase output makes it think it's moving too slow to shift up. Any other ideas?? Any solutions or suggestions?? Any help woud be appreciated.

Thanks!


Dont know if its any realation, but I had a turbo 400 in a drag car that was doing almost the same thing, turned out the valve body was bad. Mine if left in drive would shift from first to second but take a long while doing it, then immediatly shift to third, and then suddenly right back to first again. Not sure on the 4l60e but isnt it kinda like a 400 but electronic shift? Sounds almost like the same problem I had.

vss sees only the RPM of the transfer case out put shaft, in low range its 4.7 times slower than the computer thinks is right....

Got any port to plug in a code reader? That trans should be setting codes. If not yer gonna be going fishing.

If it was a bad valve body, I would think I'd have the same problem in high range. But in high it works fine.

At first it threw a "28" code a couple of times. The GM manual I have said something about an "illegal setting" for a 4l80e - nothing for the 4l60e. Another explanation I found had to do with the W vin, not the TBI. The last time I checked it - though it was only a few minutes in low range - no codes.

My thought is also that the VSS is not letting it shift. Any way around that?? An ECM from a 4X4 maybe??

Thanks for the input!

ecm from a 4x4 and a way to trip teh 4 low setting , just went through this samething with my buddy. Or you could buy advance adapters kit that takes a speedo reading before teh t-cases :)

What trannyboy said. The ECM needs to see a certain minimum speed to allow shifting. Since you aren't reaching that speed, it ain't shifting. I would assume the toy tc has a switch somewhere on it for 4wl. This needs to be tied into the ECM. If not, you will have to rig a switch to the shifter.

Pete

The other option you have is to get a custom chip burned to alleviate this condition.

The ecm expects a 2.72 drop in low range, so yours is way to slow. It will probably go to limp mode after a bit when it finally figures out that there are ratio errors.

The reason it shifts to second on command is because 2 is a full manual gear. You can take off in second gear as well.


Give TBIchips.com a shout and talk to him about your dilemma. May as well get a little extra power out of it at the same time.

Get advance Adapters #716073 to put vss at back of trans. Your setup is providing wrong spped output.

OK, it appears that a new chip or ECM won't help. The VSS needs to go on the tranny and R & R and teardown will not happen real soon . . .

What are the consequences of disconnecting the VSS while in low range?? Will it shift manually? Will there be any problems other than the CEL and throwing codes??