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Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 16873
Experience:  GCM master tech over 25 years
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I have a 86 sierra that only operates in reverse

Customer Question

I have a 86 sierra that only operates in reverse
Submitted: 2 years ago.
Category: GMC
Customer: replied 2 years ago.
1986 Gmc Sierra Classic auto trans. Literally drove it and parked, went to move it and only will back up. Fluid level is fine
Expert:  Gary replied 2 years ago.

I am sorry for the long wait and that you are having this problem

is the transmission physically being shifted into drive ? and it just acts like neutral ?

is this a 4WD ?

Customer: replied 2 years ago.
not 4wd, yes the selector moves it into forward gears, with the wheels up they start turning but it doesn't have the power to drive the vehicle. fluid is not burnt.
Expert:  Gary replied 2 years ago.

with reverse working fine we know the fluid is full and the transmission pump is good and making good pressure since reverse works

with it not moving the truck forward when forward is selected is going to be an internal failure going on of the forward clutches or possibly the one way clutch inside the transmission

the shift solenoids or valve body would not cause this problem but something inside is slipping or not being able to apply a forward gear

I am sorry to say this transmission will need to come out and apart to be repaired and usually ends up being a rebuild to correct this issue

a lot of times it is a lot cheaper to just pick up a used transmission for a junk / salvage yard and just swap it out into your truck

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