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Hi guys,

Had a new thing happen over the past few days.

When I change down under medium to hard accelleration from OD to 3 or 3 to 2 I get a vibration for about 1-2s just after its changed gear. Speed around 50mph.

I cannot verify if it does it going 2 to 1 though.

It only last a few seconds but make the whole back end shake as if you are going over a cattle grid (don't know if you have them in the US).

Now the strange bit:

It does not vibrate when going OD to 3 if I use the OD OFF switch regardless of how hard I accelerate.

I does not vibrate when I/ it changes up from any gear.

It does (I think) vibrate when it changes down under medium acceleration but not when I blip the throttle to kick it down (i.e. going up a long hill and the truck decided to change down).

Oil level in box is ok (just above the twist in the dip stick, motor running and hot).

In normal cruising its fine.

It does not vibrate when chageing down when decelerating under engine braking to a stop light for example.

Drive shaft is ok - new UJ about 6 months ago.

Oil in box was changed about 2-3 months ago.

Any ideas? How fatal is it???

Vehicle has just passed 150K miles

 

Double check your u-joints. I know they were recently replaced but it sounds like it could possibly be one going out. If that's not it . . . well I don't know what.

 

Sounds like it might be torq converter shudder. If your oil was changed two to three months ago, it might be a fluid problem. Even though most folks just put in off-the-shelf tranny fluid, most transmission shops will tell you that the E40D takes an additional friction modifier additive. They use a special brand that costs around $30 for a quart, but it elminates the symptoms you describe in a lot of instances. They typically do an additional change, then put the new oil in with the new fluid. I know of three separate instances where I have personally seen this treatment eliminate shudder/vibration.