Allison 5sp: Does this sound like the NSBU?

[Sandracer799]

I am not sure if this is the NSBU or not. First off the truck will not start in neutral, only park. Second if I was to try and manual shift it it will do fine till i get ready to go from 3rd into d the little square around the gears goes away when i try to put it in drive. It shifts into 4th but not 5th. The only way to make it go in is to put it in neutral and then shift it back to drive.

This is only when I am trying to manually shift it. It shifts fine if you just leave it in drive and go.

 

[scramHD]

hmm. nsbu would be my guess. but if it works fine in D, dont fix what aint broke.

 

[Mike L.]

Does sound like NSBU. When you manualy shift it from 1 -2-3, nothing is moving inside the Alli. Only the NSBU switch. Once you hit D N R you are actualy then moving the manual control valve in the valve body.
It is cheaper to throw a new switch in than trying to diagnose the switch. You're probably overdue for one anyways.

 

[scramHD]

For the LB7 there are two. Black and tan.

What is the difference? (I know the tan is the new one)

Is the NAPA switch the same as the GM supplied switch? Prolly not but I want to know for sure.

 

[Mike L.]

For the LB7 there are two. Black and tan.

What is the difference? (I know the tan is the new one)

Is the NAPA switch the same as the GM supplied switch? Prolly not but I want to know for sure.

The switches will interchange on the 4L60E, 4l80E, and Allison. The problem is the Allison switch has better sealing. Buy it from Allison and be assured you get the right one.

 

[scramHD]

Thanks.