98 XLT end of the line? (Transmission / drive line question)

[darrellW1]

Hello all, first thanks in advance as I have received much help from searching if the forums over last year+ You all have helped me a lot.

So, we have 98 XLT 4.0 OHV 4WD we affectionately call "Grandpa". We bought grandpa with 282,000 miles and he now has 302k! So,in short he is long over due for his dirt nap but also is now apart of the family. He always starts right up and runs strong.

Anyway, I think the transmission is starting to go but I'm wondering if it might be something simpler like u-joint(s) or 4WD hanging up.

About 1000 miles ago I went on road trip and noticed a noise similar to running over a small rumble strip when truck was shifting in or out of over drive on the highway. It was really cold (0) so thought maybe it was cold related. However I have heard it since in warmer too. Ever since that trip the center console/armrest has a shimmy that was not ther before. It vibrates side to side and seems to do it most around 40-45 mph on city streets which is also about the time overdrive kicks in.

This morning it seemed like it slipped and cluncked as I backed out of driveway to go work. Thud-thud-thud by then it caught and I moved on. ( Sorry if I'm starting to sound nuts. Thanks if you are still reading. )

I'm coming to the first stop sign I hear almost a rubber type rubbing noise from the front left. Sounds almost like driving on a flat tire but the tire is perfectly fine. Then when taking off times feels like it's slipping.

If I stomp on the gas it shifts just fine through all the gears and shifts fine most of the other times.

I don't really trust the four-wheel-drive system on this truck anymore as I have felt like it was stuck in the past. That said I have successfully used the switch on the dash to go in and out of four-wheel-drive low before.

I undid the negative battery terminal for 10 minutes just to be sure I reset it.

The guy I bought this from had the transmission fluid changed before I bought it. So that is about 25k miles ago. Fluid level is fine. It was nice red when I first got it but now definitely is dirty. No burnt smell.

Obviously I'm not gonna to put a transmission into this old beast. How do I go about testing/troubleshooting other components?

 

[cpumatt]

When my U-Joints went bad my truck would shake vigorously starting at 40-45 mph but only under acceleration.

If you wanna check if it's the u-joints just drop the driveshaft and see if the joints have play in their housing. If if does, time to replace. Either way while the driveshaft is out it doesn't hurt to throw two $10 U-joints in as long as they weren't rusty and seized in there like mine were.

If it's not that just roll it into a shop and I'm sure they'll tell you either for free or a small diagnostics fee.