By August 4, 2008 Read More →

Transmission Slips In Reverse

We have a GMC full size conversion van. We had a small transmission fluid leak at the main seal for quite some time, but always checked the fluid levels and added ATF when needed. About 3 months ago, we took it to a local mechanic and had this main seal replaced. When I picked the van up, it would not move in reverse.

The mechanic finally got it to back up, and said that it may take some time for the pressure to build back up, and to drive it for a few days to make sure (it went forward with little problems). By the time I got home, it would back up fine, and we have noticed that the leak is fixed.

We only drive this van occasionally, but have noticed that, each time we drive it, it will not back up until we have driven it for some time, and, even in drive, it feels as though the transmission is slipping. We still check the levels, and they appear to be good. Is there something that we are missing that would cause it to not go in reverse until after driven for some time, and to be slipping in drive (it continues to slip no matter how long we drive it)?

I have read about a product called Lucas Transmission Fix, which is said to stop transmission slip. Do you have any experience with this product?

Lucas Automatic Transmission Fluid Additive

Thanks in advance Marchelle,


Hi there Marchelle,

You are experiencing the first stages of automatic transmission failure I am afraid to say. Reverse gear is usually the first sign of transmission wear/failure. Once the transmission fluid gets hot it gets thinner and is easier to push through the transmission….and move the vehicle. You can try the additive, I have not used it before but it certainly wont hurt anything at this point.

They do say this about that Lucas product though “This product can not fix mechanical failures and torn seals.” Those types of products are great for preventing issues from happening, but don’t really “fix” anything. I have yet to find a magic liquid to fix a serious car problem.

I would also not recommend servicing the internal transmission filter or flushing the transmission either, since that can just make things worse! And if your mechanic drained out most of the old fluid when he did the seal replacement….that is probably why the reverse gear failed when you picked up the vehicle.

That old dirty gritty transmission fluid was acting like a sand paper abrasive against the bands/gear inside the transmission. Removing that friction/fluid and replacing with fresh clean slick transmission fluid….causes the gears to slip.

The only real cure at this point is probably a transmission overhaul or a total rebuilt replacement transmission…….or a used transmission from a local junk yard, but that one might be as worn out as yours. :-(

Driving the van on a regular basis MIGHT extend the life of the transmission though. Cars are like people, they hate to sit up for long periods of time then get up and run around all of a sudden.


Austin Davis

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."

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