Hi everyone,

Newbie here with a mysterious problem that both my regular mechanic and transmission specialist have not been able to diagnose. I hope the experts here will be able to help.

The patient is a '96 Disco V8 with automatic transmission, and 119K miles. The problem is that after being on the road 30-45 minutes at moderate to highway speed, I feel a "bump" that then continues until the trip ends. It feels either like a sudden downshift, or someone tapping the brake every 5 seconds (the intervals are irregular), causing the car to lurch slightly. It also makes it nearly impossible to accelerate from the current speed.

It actually first happened 2 years ago. My transmission specialist couldn't pinpoint the cause but adjusted the shift points, which solved the problem for a bit. It started again a few months ago. I don't do much highway driving so I've let it go until now, but I've decided to try to fix the problem once and for all. As I mentioned before, both my regular mechanic and the transmission guy cannot find what's causing the problem. Any thoughts?

 

Does the check engine light come on ? I had a similar problem but the check engine light came on and said I had a misfire on cylinder 8. I took it to a brit car shop and they first said it was the coil pack, no, it needs wires, no, what kind of plugs did you put in it, no, it's the torque converter - it doesn't lock up. So I finally said could it be sticking exhaust valves ? They said for $380 more or so we can check it out. So I brought it home, yanked the heads and had a shop do a valve job. Runs perfectly now. The symptoms were at 50 - 60 mph it would feel almost like driving over railroad ties, not quite that bad, but you know what I mean, and it would not accelerate from there. Other than that, it ran great. Of course there were the OBD codes too. This is a '96 Disco 4.0 with about 110K.

 

The fact that you were able to adjust the shift points some time ago and that corrected the problem tells me that you are about to have a tranny pronlem. I don't know if it is in the valve body or the controls for the torque convetor.
You might try driving it is 3rd. gear and see if this problem still occurs.
As for a shop having a problem finding it, a dealer, using a test book could find it while hooked up and driving.
Mike

 

Thank you both. The check engine light doesn't come on, but I don't trust it as I've had problems with the electrical as well (dash lights turn on at one click and turn off when headlights go on, etc.) I'll let the mechanic know about your suggestions.

 

Before you go to the mechanic, go drive it like I suggested, the outcome will be goo info for the mechanic.
Mike