I have an 88 D100 shortbed with auto and 318. Whan I shift from Park to Drive or Reverse, there is a HUGE bang and lurch. It shifts fine going down the road. I had an 85 that did the same thing when I was in school, but that was back when as long as it ran, I didn't care . . . . Thanks for the help!!

 

sound like a bad universal joint on the drive shaft.

 

Check the motor/tranny mounts as well

 

And if those ain't it. check the back-lash in the rear.

 

Thanks! I'll check the universal joints. How the heck do I check the back-lash??

 

Chuck the tires, then put tranny in neutral. Then grab the driveshaft (actually the pinion yoke) and see how much "slop"(backlash) you have. you can do this while checking u-joints. There should be some, but if you can move it more than quarter turn, that might be your "bang"

 

thanks y'all! I'm going to check it this weekend to diagnose a bit. Hopefully nothing too crazy going on.

 

Things in the trans that will cause this.
1. Low trans fluid level.
2. Engine idle speed too high.
3. Low and reverse band adjustment.
4. Sticking accumulator, broken accumulator rings or springs.
5. Throttle linkage adjustment.
6. Line pressure too high or too low.

 

I didn't even consider the idle speed. That may be part of the issue, as it doesn't happen all the time.