Will a defective NSBU switch make the Ally slip?

[Duramaxdiesel]

My NSBU switch seems to work when it wants to. When it works the tranny is fine. When it doesn't the tranny slips all the time when I lay on it. The dealer wants $196.00 for the part up here in Canada! Any ideas if that sounds right? :confused:

[mdrag]

Duramaxdiesel,

Your post did not mention if your truck is stock. If not, what mods do you have?

From your description, it does not sound like the NSBU switch is the problem. The NSBU switch sends the position of the shift selector shaft to the TCM. More Power's write up on the NSBU (http://www.thedieselpage.com/members/features/nsbu.htm) explains troubleshooting and replacement. Also a forum search on this topic should yield a number of hits.

Not shifting into fifth gear is one of the reported symptoms of NSBU failure. With the slipping you describe, I'd suspect the clutches or torque converter as the possible culprit.

Good luck.

[Duramaxdiesel]

I should've been more precise. My truck is stock-for now :D When the truck is cold my gear indicator works fine. As I drive though and the truck warms up the indicator disappears. The indicator for reverse works. When I put it back in drive it goes in hard, not at all or won't let me get above third gear. Oh, and it slips. On a good note I found an Allison dealership in my area who is selling the NSBU for $84.00 instead of $196.00 that the dealer wanted.

[mdrag]

A few more questions: Has your truck been checked for error codes? If not have it scanned. How many miles on your truck? Have you checked the ATF fluid level? Have you changed the ATF? If so, what are you using? Has the spin on filter been changed?

The shift position indicator problem points to the NSBU switch. Someone with more Allison know how will have to comment on the slipping problem

[Duramaxdiesel]

Sorry for the late reply Mdrag. I had the truck scanned but couldn't stay with it. Dealer didn't charge me but said that the NSBU switch is defective. This is the interesting part: I HAVE the newer tan switch and its no good. Has anyone else had the newer switch go out?

I checked the fluid and all was good. For the time being I'm using Castrol DexronIII and have yet to replace the spin on.

P.S. On Sat. I was stuck in 3'rd gear. Had to drive 25Kms like that. No fun. :mad:

[DmaxMaverick]

....and have yet to replace the spin on. Sounds like you might have found the source of your problem.

Allison recommends the filter be changed at 5000 miles, or the symptoms you describe may occur. Don't forget the magnet!!

[heartbeatcanada]

Ya i've gone through a new tan one before. Stuck in 3rd, but still plowed 12 more hours in limp(sunday and no nsbu switch available). I now carry a spare one with me. Its good you got it at an Allison dealer, as you found out the dealer wants 2-3 times the amount you can get it at Allison. Later Jeremy