cove

#1 Factory manual says trans control unit(TCU) malfunction can be diagnosed with a DRB II tester. What is a DRBII tester?


#2 Can TCU be reprogrammed to shift at different speeds to compensate for larger tires? Are programmable units available?


#3 Transmission clunks when put in gear from standstill. Can the idle speed on the fuel injection unit be lowered?


Thanks for any help you may be able to provide. - Cove

RRXJeeper71

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Unknown XJ

Found this sir or ma'am:
https://www.cherokeeforum.com/f2/drb-ii-scanner-109422/

To answer your second question, I really doubt that you can adjust anything in the TCU let alone the ECU.... If you want larger tires and what not, you need to regear your axles (and replace the rear axle if you have the D35) C8.25 is a more budget friendly option but there's less aftermarket support or parts. There are several other options out there but,it really depends on what you are wanting to do with your rig. And its a little bit more than I care to get into ATM LoL.

For you third question, if you have a high idle I would start with cleaning your throttle body and your IAC (Idle Air Control) make sure you don't bend the rod on your IAC when cleaning, removing it, or reinstalling it. Here's how to adjust the transmission btw...... https://www.cherokeeforum.com/f2/free-quick-fix-41821/

cruiser54

It's the factory Diagnostic Readout Box.

No programming can be done to the TCU.
Ever adjusted your TV cable?

Make sure you don't have bad engine and trans mounts and/or bad u-joints in your rear driveshaft.