Transmission shifts to OD at 35 mph?

scottyknows50 · 11-19-2009, 10:18 PM

The transmission on my '87 Cherokee has been shifting strangely- when I am trying to merge on the interstate it quick shifts up to overdrive by the time I reach 35 mph. Flooring it doesn't do anything. If I leave the shifter in 3rd it will rev and shift normally and I can put it into OD when I'm on the interstate. What would cause it to shift up so quickly and not want to downshift? Anyone else experience this? Thanks. It's the AW4 tranny- I believe.

**balloo93** · 11-19-2009, 10:47 PM

TPS is more than likley going out. You can check it with a volt meter.

Jeep Cherokee TPS Adjustments

pentastar01 · 11-19-2009, 10:50 PM

Try adjusting the kickdown cable. Sorry, but I don't know how to, somebody should.

1990JEEPXJ · 11-19-2009, 11:08 PM

flip the tranny switch to power mode while youre at it. but i think it also has to do with the TPS.

scottyknows50 · 11-19-2009, 11:11 PM

that tps seems to be a troublesome bit........

1990JEEPXJ · 11-19-2009, 11:13 PM

yes on renix XJ's especially. they are adjustable as well so you cant just throw it in. youll need a voltmeter to put it in and have it operate correctly. its fairly easy though

scottyknows50 · 11-19-2009, 11:30 PM

i guess i need a voltmeter

**balloo93** · 11-19-2009, 11:36 PM

If you own a Renix (87-90) you need a volt meter. You can troubleshoot damn near any propblem with a volt meter on the Renix. IMO it's a must have.

carnuck · 11-20-2009, 12:50 AM

TVS cable out of adjustment or kinked (tighter it is, the lower speed the upshift)

cruiser54 · 11-20-2009, 05:57 AM

Check the "trans" fuse in the fusebox to see if it's blown. I found that my power/comfort switch was shorted internally and blew that fuse. The Jeep defaults to the comfort mode without power to the switch circuit. It's easy to remove the faulty switch and do a permanent bypass on the switch plug.

scottyknows50 · 11-20-2009, 09:29 AM

Quote:

Originally Posted by cruiser54

Check the "trans" fuse in the fusebox to see if it's blown. I found that my power/comfort switch was shorted internally and blew that fuse. The Jeep defaults to the comfort mode without power to the switch circuit. It's easy to remove the faulty switch and do a permanent bypass on the switch plug.

good thing to check- i have never been able to tell the difference when i switched between the two. maybe my fuse is blown. i removed and cleaned my tps and i'm thinking i put it back on incorrectly- will just need some adjustment i hope.

cruiser54 · 11-20-2009, 10:00 PM

If you don't notice any difference between power and comfort modes, I bet the trans fuse is blown. Shifts up quickly and drives real doggey in comfort/default mode. I would suspect fuse before TPS but it ain't a bad idea to set your TPS anyway. If the switch is bad/fuse blown, pull the switch, remove the connector and jump the two wires in the harness connector that aren't solid black. Then replace the fuse and you wil have permanent power mode.

**balloo93** · 11-20-2009, 10:02 PM

If the trans computer is toast or the fuse is blown it will stay in 1/2 and will not shift unless you manually work the shifter.

So if it's bad and you start it up and put it in OD the thing will bogg or stall. If you start it up and shift to 1/2 then 3rd then OD and it runs great then you know the TCU is not working.

cruiser54 · 11-21-2009, 06:00 AM

balloo93 made me think of something. Have you looked for the "other" trans fuse also? It's taped to the harness up under the dash by the passenger side knee bar. Easy to find. Make sure it's not blown and the connections are clean at the holder.

scottyknows50 · 12-02-2009, 11:46 PM

my TPS output voltage won't go below 4.1 and the input voltage is at 4.6- a ratio of about .89. i know it's supposed to be .83- does this mean that i need a new TPS? how much do they run?