Sounds like a sprocket in my 2008 Yukon denali striped out. Goes in reverse but not forward

SOURCE: lost reverse on GMC Yukon Denali vortex drives

WOW sorry to hear that.

this is a common problem with the 4l60e transmission, what has happend is the gear has sheared off the back of the sun shell, you should have lost reverse and if you will watch your tachometer the next time you drive you will notice you allso lost forth gear.

you will nedd to have the transmission removed and disassembled for the new sun shell, make sure you get the hardened sun shell, this is not a rebuild but simply a repair. you can get a stock sun shell for about $65.00 or a heavy duty one for about $100.00, make sure you find a good tranny guy to provide the labor, oh the transmission paper rubber kit "reseal kit" shouldnt be more than about $80.00

good luck

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SOURCE: 02 yukon denali security light stays on will not

Several GM products, including the Chevrolet Impala and Malibu, the Oldsmobile Alero, the Pontiac Grand Prix, and Saturn Ion, have issues with the Security light coming on. This is many times an indication of a failing Body Control Module (BCM). Initially, the Security light will come on then go off, progressing to a constant on light, before the car will refuse to start. Other symptoms may include erratic action of electronics, a clicking sound coming from the glove box, and the air conditioning failing to blow cold air. I recommend a shop that specializes in the electronic systems of vehicles to diagnosis and make the necessary repairs. They should keep the car until they replicate the symptoms described. A new BCM from GM should cost about $230; plan on another $200 for them to diagnose the problem, replace the unit, and program the new unit. The dealers quote between $700 and $1,100 for the same repair. My experience and the experiences I have read on the internet, indicate the new BCM should last only about a year.

Marvin

• 85242 Answers
• Posted on Aug 27, 2009

SOURCE: my 2002 yukon will not go in reverse--

this means the reverse clutch has failed, u are going to need the trans overhauled to fix the problem and the lines and trans cooler flushed out along with the torque converter.

SOURCE: What the normal transmission temp Yukon Denali XL 2008

TRANSMISSION FLUID NORMAL TEMPERATURE IS 200 DEGREES.

SOURCE: 2001 Yukon Denali: The security light came on my 1999 Yukon Denali ye...

The security system (Passlock) is having problems, it's typical on those trucks. You can find a great write-up here: http://newrockies.ca , it was the only thing that saved my Park Avenue.