2004 GMC sierra 2wd.
Repairs = Haven't made any attempts at repair yet. Asked a question here before.

2004 GMC Sierra 2wd 1/2 ton 4L60 trans.
Transmission shudders going from reverse to drive
when cold. After it warms up some it doesn't do it as bad if at all. It has started to slip in reverse
and forward gears, usually at slower speeds, around corners or starting uphill.

It was starting to act up prior to a filter and fluid change about 3,000 miles ago. The trans pan
looked fairly normal as far as the amount of clutch sediment for a 100k service interval. The
fluid level is good and no apparent or visible leaks. The fluid also smells/looks normal. With the
theft of my scanner, I have no means of pulling any diagnostic codes out of it. Any ideas? Pretty
frustrating. Never had any trouble out of it before this.

Answer:
Sounds like a possible problem in the forward accumulator in the valve body. Possibly binding,
or  a seal has rolled. Or a problem in the forward clutch or forward clutch piston.

There is also a service bulletin for a failed reaction sun shell, gear and or bearing. But this
usually will be a no reverse condition. Although the problems you are having may be a
pre-cursor to it failing. Would need to be disassembled and inspected for these areas.
Answer:
Your truck is too old to have an
electronic throttle control system. This problem would not be
caused by that anyway. It could be the throttle position sensor (TPS) but that will usually set a
check engine light and code. You may be running into the Rev limiter, since you are talking
about 100 MPH.

The computer would shut off the fuel injectors or ignition to prevent excessive speed and
engine RPM. If that is your condition, there is no way around that other than getting an
aftermarket PCM re-flash of the computer. Some companies offer a way to get around that
limiter, but not all. You would have to check with the different companies to see what they off.
It is usually a speed or custom shop that does that sort of thing.


1999 GMC Sierra 4.8L Vortec. Truck falls on its face at 100 mph only for a few seconds then
kicks back in again till 100mph then wont take fuel. Could this be throttle actuator or
accelerator pedal sensor

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2004 GMC Sierra Transmission Shudders