aw4 1-2 early shift

I have a 96 XJ 4.0 with an aw4. The tranny shifts just fine when it is in "drive" or "3". It will upshift and downshift just flawlesly. The problem I am having is when the tranny is in the 1-2 position. Here is the problem that just started happening:

Start from a dead stop and accelerate at a moderate pace. The tranny will upshift from 1 to 2 at a very early 2000 RPMs. If you keep accelerating to just over 3000RPMs the tranny will then downshift from 2 to 1. At this point in time the engine is screming, my emotional words, as it is trying to engine break since the jeep is going way to fast for that tranny gear. In the past I can remember that the jeep in the 1 - 2position would upshift from 1 to 2 at around 4200 RPMs.

Any ideas on this early upshift and then downshift problem?

Thanks Tom

change the tranny fluid?

You don't by chance have the NSS bypassed? A dirty NSS might cause this problem too.

lawsoncl said:

You don't by chance have the NSS bypassed? A dirty NSS might cause this problem too.

Click to expand...

Should I just spray it with some electric cleaner or wd-40?

Thanks

lawsoncl said:

You don't by chance have the NSS bypassed? A dirty NSS might cause this problem too.

Click to expand...

The nss has nothing to do with shifting. I have 2 rigs that have had the nss bypassed for 2+ years with NO shifting problems.

The only thing the NSS controls is starting and back-up lights. The TCU contols shifing. The TPS helps to control shifting. The kick-down cable out of adjustment will have negative effect on shifting. Several other thing have impact on proper shifting.....but not the NSS!

The NSS does tell the TCU if the shifter is in (1-2) or (3). A few folks have reported odd shifting like this with the NSS bypassed and the shifter in (1-2) or (3). I think this is probably year-specific since unhooking mine makes no difference in shifting.

Since he mentioned it only happens with the shifter in (1-2), I thought it a reasonable question to ask.

The problem was solved with replacing the NSS. Thanks for pointing me to a possible problem, as it was the problem. I tested the NSS via the ohming tests in the factory service manual. I found out that when I ohmed the 1-2 position, it was open, which is bad. I also found out the Reverse was open when the gear shifter was in "R", this is also bad. I never noticed that my reverse lights were out, but they were. Also the NSS ohms for 3rd gear was pretty high, but still registered as closed. The new NSS I bought from team cherokee ohms at 1.5 for all the correct and closed contacts. The problem with the bad switch was one of the springs, as the lower set of contacts share a single spring for "Reverse", "3" and "1-2". The top set of contacts are for "Park" and "Neutral". Park and neutral worked just fine.


Thanks for all the help.

Tom