intermitent failure to shift to park/ allison

[lb7lbz]

i have a 01 dmax/allison w/208000 miles. every once in a while when i try to put it in park it will not go in, i left the truck running in neutral went in to a store came back out it went right in no problem. this wasnt the first time this has happened either. any ideas?:mad:

[DmaxMaverick]

The NSBU could be failing mechanically. Also check for damage/wear to the shift cable and shift lever pivot and linkage. If you have a LOT of play in the lever when it's in P, you may have a worn out lever, pin, or linkage part. A remote possibility could be the brake pedal lock-out, but I've haven't heard of one ever prevent getting into P.

[Mad90]

Had the same problem w/my 01. Was the shift selector switch inside tranny. contacts were shorted. Are you losing dash indication of range? Mine would not show what gear you where in. Truck acted like it was in limp mode

[DmaxMaverick]

Had the same problem w/my 01. Was the shift selector switch inside tranny. contacts were shorted. Are you losing dash indication of range? Mine would not show what gear you where in. Truck acted like it was in limp mode
Your problem was the NSBU. It is a "switch" outside the tranny. Your symptoms would have indicated a failed NSBU. I think lb7lbz is experiencing a different problem, although it could be a mechanical failure of the NSBU, not electrical contacts such as yours.

[lb7lbz]

no problem with the range indicator, however i did have a similar problem about 100000 miles ago had to crawl under truck and hit linkage on side of tranny no probs. ever since till now. also sometimes i have to tap the brake pedel before the cruise control will engage so maybe it is brake related. i'll try to get a better look at things next time it happens

[lb7lbz]

ok guys, since i last wrote in this condition has happened prob. 3 times. i have noticed if i shift it back to neutral tap the brake it will then go right in to park. so what do ya think? brake switch? like i said before i also have to tap the brakes to get the cruise to work,just dont want to replace something that aint broke. thanks 210,000 miles and climbing

[77TransAm]

Can you describe your condition in a bit more detail?

When you attempt to put the truck in Park, does:

- the transmission go in Park, but the indicator does not?
- the shifter hit a hard stop before it can go in Park?
- the shifter "run out of room" before the transmission goes all the way in Park?

There are no detents in the steering column or the cable - the only feel you get for the different gear selection is from the detent lever inside the transmission. If you can't quite feel that last clunk into Park, I would first suspect the shift cable; it can become worn, or just filled with grit and debris over time. Since the cable has to push the transmission shift lever into Park, a malfunctioning cable will often show up first when trying to do that.

Take a look at the cable where it snaps through the bracket at the rear of the trans and make sure both tabs are still present and securely latched in place. If they are, you might ask someone to shift through the gears (preferably with the engine off) while you watch the cable under the truck. You can often see excessive movement or binding if the cable is not able to make that last push into Park.

Another (less likely) possibility is that the nut holding the detent lever onto the selector shaft inside the trans has loosened. I doubt that would happen after so many miles, though, and I believe you would see issues on both ends of the shifter (P and 2-1) if it did.

[lb7lbz]

the condition is this; try to shift the truck from drive to park and once in a while it hits a hard stop before it gets there.shift it back to neutral tap the brake pedal and it shifts in no prob. this only happens maybe once every two weeks,also sometimes when i try to use cruise control it wont engage again tap the brake pedal then try it , works fine. i guess thats why i was thinking brake lockout switch

[77TransAm]

OK, that condition is a bit different than what I described. You're right - it sounds more like the solenoid that keeps you from shifting out of park without stepping on the brake.

I've never heard of that happening before, but combined with your cruise control problem, I would also be looking at the brake switch.