Nearly Free XJ

I recently received a nearly free XJ. It molested a cow @ slow speed and needs some eye shadow but I am looking for AW4 transmission answers. According to the previous owner it quit shifting. He install 1 used trans, then 1 rebuilt, then a new computer under and then it started shifting again. After a wile the shifting stopped and another puter was installed. Now the shifting has stopped and it is mine. I discovered that it will shift manually. Before i dive in head first are there any suggestions on a starting point. As it sits there is a freshly rebuilt trans and at least 1 new computer. The owner didn't know witch computer was replaced the one under the dash or the one under the back seat. I have done nothing yet and breathlessly await your input.

Sorry forgot to include specs. 1990 XJ Wagoneer, 4.0, aw4, 242, dana 30 front, dana 35 rear with sun roof and wrinkled.
THX


PS Merry Christmas

On my xj,it wouldn't upshift,I replaced the throttle position sensor and that fixed it.Mine is a 92.

The TPS has alot to do with the Trans Shifting. their cheap from a parts store.

Put a new radiator in yesterday will do so with a TPS I have on hand and see. Last night it would not down shift to take off from a stand still on it's own, if shifted manually it seamed to do fine. If all things work out I'll have a gray one wit no interior or drive train to use for rehab. I would like to find another Cherokee Wagoneer Limited to get the dual headlight set up out of. Thanks for you input.