i have a 94 with about 155,000 miles on it and this started yesterday, but when i am cruising at 35 it seems like my truck will downshift and then run really rough, it only does this in between 35-40. and when i try to gain a little bit of speed i have to floor it to even start gaining speed again... i think my tranny is going out but not sure... if anyone could help me figure this out it be very helpful

 

If it's engine related I'd think you would be able to reproduce this in other gears / speeds. Does it happen at only that one speed / gear?

Rich

 

If you have an automatic trans it may be that the overdrive is not functioning properly. I would start by checking your tranny fluid make sure that it is full and that there is no black **** in it. If the tranny fluid checks out ok then I would make sure that you didn't accidentally turn off the overdrive.