96 s10 blazer slow reverse

I just had the intake manifold gasket replaced then a couple days later when I get in the car in the morning it shifts into reverse and starts to go as it normally would but when I press the gas it just revs the engine. After this happens everything is fine for the rest of the day. It sounds like the engine is sucking in a lot of air which leads me to believe spark plugs but I don’t know if that would cause my reverse problem, I’m hoping it doesn’t mean my transmission is shot. Any suggestions on what’s wrong are appreciated!

First off, spark plugs are the last thing I would suspect. You need to have your transmission fluid level checked. (I’m assuming it’s an automatic.)

Does it work fine in the forward gears?
Has the problem with reverse happened more than once?
Yes, get the transmission fluid level checked ASAP.

Just checked the level and it was full. This happens every morning, but going forward it does fine, this problem happens only during the morning, otherwise everything works fine the rest of the day.

Did you check the level with the engine running and warmed up? It will read a lot higher with the engine not running. It’s a different procedure than checking the engine oil.

The car was running and had been for about 30 minutes, and the car is old enough to where it still has the dipstick for the transmission fluid so that is how I checked it.

How many miles on it? Is the fluid red or is it brown with an acrid odor?

About 126,000 miles. The fluid is slightly brown (not black), with no acrid odor.

This may answer your question @Thumper2009.

If the transmission fluid is brown and not red, it means the transmission fluid is burnt or used up.



Engine sounds like you report could be some kind of intake manifold vacuum leak. It wouldn’t be that unusual for a shop to forget to connect up some vacuum line or another. Or the re-gasketing job could have been botched. Not very likely, but something to consider at least.

Vacuum leaks are a very common thing so shops have various methods to check for vacuum leaks. Measuring the intake manifold vacuum reading, using a vacuum pump to check vacuum operated devices for diaphragm leaks, using propane tests, etc.

Edit: You don’t notice anything usual with the brakes, right?

Whether there’s a relationship between the sound you are hearing and the transmission symptom, hard to say. It’s probably just a coincidence. My guess, you haven’t noticed it until now b/c the weather is getting colder now.

Another idea, really a wild guess on my part, my truck’s automatic transmission has a vacuum line going to it. I think it has to do with the downshift operation when accelerating. But maybe yours has some vacuum requirement to function correctly, and if your intake manifold vacuum is reduced for some reason, the same reason causing that sound you haven’t heard before, that might affect reverse. It’s a reach, but something to at least consider.