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Bob, Auto Tech
Category: Chevy
Satisfied Customers: 4087
Experience:  Plus 40 years GM, over 30 certified with Chevrolet, ASE certified Master Tech. (Expired, Retired)
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Chevy Suburban: reverse gear..What are possible problems and fixes

Resolved Question:

Chevy Suburban 2000 won't go forward, only reverse gear works. What are possible problems and fixes?
Submitted: 8 years ago.
Category: Chevy
Expert:  Bob replied 8 years ago.

Very first thing to do, is to look at the cable where it connects to the side of the transmission and have someone in the truck run the lever through all of the selections while you watch and see if the cable is moving the lever it connects to where it goes into the side of the transmission case. It is possible that it has come loose and will only pull in one direction. If the cable is working ok. Check the fluid level. If it too is ok, then the problem is going to be inside of the trans and it will need a tear down to be inspected, or at least the trans oil pan re,removed to see how much can be seen with the pan off. The most common causes are listed below for you. This may not be everything that can cause this condition, but it is a list of the most common ones seen by GM and posed in the service manual for your truck. The very last one on the list refers to the reaction sun gear carrier and that may be the biggest problem they have with both the 4L60E and the 4L80E transmissions. It is a problem the fought for a long time and they now have a new and redesigned heavier duty part available for replacement, if that is the problem. You will be looking pretty much at a major over haul if that is the case. Thanks


No Drive in Drive Range



Oil Pump (4)

Damaged vanes
Missing slide spring
Oil pump screen assembly plugged or damaged
Oil pump rotor guide omitted or misassembled
Oil pump rotor cracked or broken
Porosity in fluid pump
Oil pump surfaces not flat
Excessive oil pump rotor clearance

Forward Sprag Clutch Assembly (642)

Damaged sprag
Worn or pitted inner race

Input (662) and Reaction (681) Carrier

Damaged or worn gears

Customer: replied 8 years ago.
Thanks. Since there was no warning signs and this happened all the sudden is it more probable to be something simple like the cable coming loose (or low fluid) or does a more serious problem like the reaction sun gear carrier have a failure signature like this?
Expert:  Bob replied 8 years ago.
As much as I wish I did not have to say it, chances are much greater that it is in the reaction carrier than the cable. But, you want to check the little things first, just to be sure and you can always hope. Many of the internal parts will let go, with no warning what so ever, before it happens. In the case of the sun shell carrier, it is just a matter of the component not being heavy duty enough to do the job and it just explodes, no noise, no warning, nothing. Works great now, stop at a signal and step on the gas and no go. There are other things that can cause it, but not nearly as common. You could even get lucky and find the transmission filter laying in the bottom of the oil pan once the pan is removed. If you have to have someone else do the work, just be sure you deal with someone who has a good reputation and is ASE certified. That is no guarantee, but at least you know they had to know enough to pass the certification test and that is not easy. If there is anything else I can do to help, please just drop me a note. Good luck and thanks
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