No Forward or Reverse

[cfunderb]

I have a bullydog chip on my truck. E40D automatic. I was passing a car at full throttle when I heard a loud thump. At first I thought that the car had hit me, but then I realized that I was losing speed and couldn't speed up. I eventually stopped but couldn't get any gear to engage. Tranny fluid looks ok. I visually inspected the shift lever and it's moving when different gears are selected. Any thoughts?

[erics diesel]

if its a 4x4 check the t case i had one blow out on me in an old jeep that i had did the exact samething going down the interstate loid thump sound then nothing

[cfunderb]

Thank you!

Looking at a diagram of the transfer case, it appears to be pretty complicated. Anything in particular I should be looking for?

[madpogue]

Try it in 4HI and see if it'll propel the truck on the front axle. Run the t-case shifter through all the positions, just to see if something feels out of place. There's an active thread on one of the diesel forums, some fella's t-case keeps popping out of 2HI when he decelerates. Not sure if it's been resolved, but you might be dealing with something similar.

Did you at least look under the truck with an assistant attempting to "drive" it, to see if the output of the t-case is turning, or if something is up with the rear driveshaft?

[cfunderb]

Now that you mention it, I've never been able to put in 4HI or N, only 2 and 4LO. I'll try it in 4LO with the front hubs locked and see if that makes a difference. Thanks for the ideas!

[cfunderb]

4 wheel drive didn't help.

[madpogue]

Duh I just remembered another thing you can try with an automatic - see if Park holds the truck in place. If you put it in Park, and you can still roll the truck (may need a buddy or two to help push, or a push vehicle), then it could be the t-case stuck in neutral, or just broke internally. If the truck holds still in Park, then t-case is probably good and it's time to start looking at the tranny.

[cfunderb]

Park does hold it in place. You can hear the park 'gear' engage. I don't hear or feel anything engage when switching into any other gear.

[erics diesel]

my next thought would be either the tranny pump or torque converter blew out but im not sure how to check either one of them