Help with shaking

Just got a '90 model laredo about a week ago. The only real problem with the truck is a shaking problem. Have searched a few different forums and haven't really found anything. When I first got it it was not wanting to shift up from 2nd gear, but was only doing it every now and then. It would do it about every 40 miles or so and would quit after a few minutes, or if it was revved almost to redline. It hasn't done that in a few days but now is starting to shake in any gear above 2nd. Only does it on acceleration, does not shake when you let off of it or at high rpm like when passing. Also I can feel it trying to shake when sitting still and can hear a pecking. I was hoping someone here has experience with this problem. I did notice some slop in the front driveline, and have already replaced one tie rod end and sway bar links and bushings. Any help is appreciated greatly.

Guessing it is an automatic from the description.

How are your motor and transmission mounts?

Have you inspected the driveshafts and u-joints?

How is the fluid level, what is the color, and does it smell burnt?

You can test to see if the problem is electrical or mechanical/hydraulic. Under the dash, passenger side, there is the TCU--transmission control unit. There is an in-line 10 amp fuse on a yellow wire running to it. Pull the fuse, drive it, and if it shifts OK then the problem is electrical--TCU, wiring, TPS, NSS, and the solenoids in the transmission. If the problem persists, then it is mechanical or hydraulic.

Sorry for not mentioning, but it is an automatic. I have heard about the problems with the tps so all the electrical is on the list to check. The fluid looks good. It's still mostly red and doesn't smell burnt. Also going to try re grounding eveything because the main cable going to the block doesn't look very good.

Well, the Renix loves its grounds!

Dipstick tube: ICM, ECU, o2 sensor are all grounded there.

Back of head to firewall: Self-destructing braided strap, replace it with a 4 ga cable.

Note: that crummy braided strap is the only ground to the unibody! Add a second ground from the battery to the passenger side fenderwell, your Renix will love you for it.

Make sure all of your cables and grounds are clean and tight. 4 ga welding cable is great, you can make some up, have some made, or do what I did and buy a complete set from 5-90's website. Great cables.

Already got cables to one just need to cut and crimp. Have some off an electric forklift that will probably work. Don't believe they're quite 4ga but there not far off. I'm planning on starting with grounding because most of the insulator on the the main cable from battery to engine is gone. The braided cable actually looks like it's in decent shape but while I'm at it it's going to. Have some cross over battery cables from the same forklift that might be the perfect length for the fender and firewall grounds. Just need to check them because I can't remember what ga they are.

Check out this article, really good info, especially for the Renix XJs.

http://www.olypen.com/craigh/charge.htm

Driveshaft u-joints. Check for play.