Im trying to diagnose the transmission problem on my truck. When I am driving up steep hills the tranmission hesitates to gear down, it is an automatic and jumps to third and sometimes quickly down to second. When it jumps down a gear and I try to maintain the same speed there seems to be a loud rattling from under the vehicle, im assuming its coming from the transmission. The higher the RPM's the louder the rattling so I let off the gas and slowly climb the hill. This only happens on steeper hills when the transmission has to downshift, also struggles more with weight in the back, i.e. snowmobile. I have been researching and this might possibly be a torque converter issue?

 

Try turning the OD off(light ON) when climbing grades of 3-6%,and drop a gear (pull shift lever down to 2nd gear.The rattle is the engine "lugging" BAD.try these few suggestions and see if it helps,just a thought................

 

fixed the plenum yet?

 

This "rattle" you talk about sounds like a good case of spark knock, caused by a bad plenum gasket.

 

i have not changed it, but I also dont loose much oil and it seems like anyone with a leaking plenum seems to burn through a lot of oil?

 

I would take a look down the throttle body, and if it looks even remotely questionable, yank the TB, and have GOOD look...... see what you see. Not everyone gets all the symptoms.