View Full Version : how does the selecttrac tcase work?

03-16-2006, 03:41 PM
I know this sounds so newb, but I'd like to know how the set up is. I've got a 90 cherokee with selecttrac and auto tranny and auto hubs. When I was under the jeep the other day with 1 tire jacked up the front dshaft turns with the tire, even with tcase in 2wd.
Is that what should happen? I thought there was a vacuum disconnect at the diff that would only engage the dshaft with the axles when in 4wd?

Can anyone enlighten me on the operation of this system?


03-16-2006, 05:02 PM
I can't remember which model case the selectrac badged Cherokees are but if it is the 231 tcase only part time ( gear selections - 2wd - 4wd high - neutral- 4wd low) the frt dif has vacum disconect if it is the 242 tcase part time full time case ( gear selections - 2wd - 4wd part time high - 4wd full time high - neutral - 4wd part time low) then the frt dif does not have vacum disconect frt wheels always engaged with drive shaft.

If it is 231 then the common problems are the vacum switch on the tcase sticks or the frt diff vacum motor siezes or the shift fork in the frt diff wears out.

Taz Jeep
03-16-2006, 05:11 PM
Select trac = 242

Command trac = 231

03-16-2006, 05:15 PM
Cool Rob I never deal with the badged name always the model number so then the selectrac is the 242 that woud mean that your frt diff is always engaged even in 2wd just the tcase doesn't drive the frt shaft in 2wd.

03-16-2006, 05:22 PM
thanks for setting me straight on that. i do have the 242 so the front dshaft is permanently engaged with the front axle. sucks!

another question....are there manual hubs available to convert my cherokee? and what are the opinions regarding the practicality of this- is it worth doing?

03-16-2006, 06:15 PM
The manual hub kit for your diff is not worth doing and there is nothing wrong with the diff always being engaged your diff is actually a little stronger than the disconect diffs and the only disadvantage is that the frt driveshaft u joints will wear a little quicker.

03-17-2006, 09:34 AM
Thanks again for the info and a couple of things make sense now. I've had this 'scraping noise' from the front end of the jeep lately, sounds just like a rock caught between the brake splash shield and the rotor, and only comes when I turn right.
I jacked up the front and checked for wheel bearings and they were both very tight. ball joints, etc - all good.
Took off both calipers and rotors, couldn't see anything that would make that scraping. Button it back up and damn, that freaking scraping is still there.
gonna check that front driveshaft this weekend.

03-20-2006, 01:28 AM
if u havent already, also check the front axle u-joints for play as well.

03-20-2006, 09:23 AM
thanks for the tip. I did check one of them - don't know why I didn't check the other. I will have a look.