The 4L80E in my 97 2500 Silverado occasionally will not readily shift into overdrive and will sit in third on straight level highway unless I either give the throttle a quick prod or the truck goes down a slight downhill slope that it will shift into OD. Otherwise the tranny shifts smooth and quiet. Any idea what the problem could be? I just had the tranny flushed and filter changed, but it was doing it before that too.

Thanks in advance.

 

Yes Sir,

Can't begin to tell you how many times I've had this complaint. Change your fuel filter.

Allan

 

Already been done. As a matter of fact, the fuel pump was replaced last summer as well.

 

Does this truck have oversized tires/wheels?

Dunno, I think something is really upsetting the shift strategy on this guy.

Allan

 

Nope. Truck is bone stock other than a K&N. If it was an older model I'd say it would have something to do with vacuum pressure. It seems to shift into OD ok when little or no torque is being applied.

 

How 'bout a plugged set of cats? (Just tryin' to help ya think.)

Allan

 

Wouldn't the back gasses as a result set off the O2 sensor(s) resulting in a check engine light as well as possible backfiring?