As I was coming back from work on Friday night the truck started to vibrate as soon as I was trying to accelerate. I was going at approximately 60 mph, and I was less than 2 km from home when it started so I made it back. On the moment I thought I was losing one of the wheels, but I tried to make the vibration come back but wasn't able.

On Saturday morning, I removed each wheel, cleaned it and put it back on for safety purposes, in case I was really losing one. I also checked the u-joints for looseness or if one was stuck. Went wheeling in the afternoon, no vibration at all.

Today I went at my mother in law's and the vibration returned. I've been able to isolate the conditions for it to happen:

- The engine has to be at normal running temperature
- The truck has to downshift and go back to overdrive (like when going up a hill), it doesn't do it when driving less than 50 mph

Now it seems to be engine or tranny related but I'm really puzzled with that issue. The truck didn't throw any code, the only codes there are my O2 codes. I ruled out possible fuel pump failure since the truck is not hard to start and does not stall when coming to a stop. Any ideas are more than welcome...

 

What year, how many miles and has your front drive shaft been rebuilt or replaced?

 

Judging by his avatar it is a DI.
He is from Canada and he has a '98 if I remember correctly.

Sounds like a tranny issue, have you checked the fluid level? When was the last time the trans fluid and filter were changed?
Kinda sounds like a torque converter issue maybe.

 

Your memory serves you well Spike. I own a 1998 D1. It has 156 000km which is 94 000 miles. By the color of the fluid (clear red), it was definitely done by the previous owner. I planned doing a tranny fluid change this week, since I don't know the last time it was done. I'll let you know how it turns out. Thanks for the advice.