Piston Slap: Old Trannies and the Full Monte
John writes:
I was given a 2001 Monte Carlo about 1 year ago. I have put on about 10,000 miles (186,000 miles now) and the transmission no longer goes into overdrive. I don’t believe the previous owner ever had the trans serviced. I am thinking I should replace the fluid and filter however I am afraid that could cause additional problems. Any advice?
Sajeev answers:
This question reminds us all that we must service our trannies on a regular basis. And to not be uncomfortable when someone asks for $100 to do the deed.
For an older car in this condition, cracking open the tranny equates to signing its death warrant. The ATF (automatic transmission fluid) is more varnish than lubricant by now, and replacing the fluid (even if you don’t flush it all out) will send the Monte Carlo’s clutches down a short, painful road. And the end of that road is a junkyard.
I’d drive the Monte Carlo until you lose third or second gear. If you love the beast, don’t cheap out and get rebuilt transaxle from a nobody: make sure the rebuilder is an expert on your model, or you’ll likely regret it after the usual 12-month warranty expires.
Bonus! A Piston Slap Nugget of Wisdom:
I shouldn’t make this a GM-only thing, although the hoopla about their “sealed for life” transaxle in the 1997 Chevy Malibu doesn’t inspire long term confidence. American cars are (were?) known for their honest serviceability, and some of us don’t care for marketing spin on a bean counter’s dipstick deletion. Some think it’s a good idea to examine tranny fluid on a regular basis: the penalty for neglect isn’t worth it. In the long run, of course.
[INSERT BEGGING FOR MORE QUESTIONS HERE. MEHTA@TTAC.COM]
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I agree with changing fluid yourself. cheap as dirt. Even if you get solenoid to work again My Mom's old Sentra started not shifting at all, about 100k, and there was 1/2 of sludge in the pan. Changed it twice in two weeks to get higher % out. Ran fine for rest of life- another 30k.
I'm fairly sure that trans fluid is not the problem - if it were, it would be acting up everywhere, not just failing to shift into OD. You need to get a scan tool and see what's inhibiting the upshift. On some cars, a "noisy" throttle position sensor (TPS) signal will prevent shifting into OD (the trans computer thinks you're goosing the throttle, when it's just a jumpy electrical signal). As far as changing the trans fluid goes, I would do it only if the fluid is brown-looking and smells scorched. Also, when you flush out the old stuff (you'll need to remove the top trans cooler line on the radiator side tank, connect a hose to it, and run it into a bucket ... then start the car, put it in N, and pour about 10-12 qts. of new fluid into the trans while the old junk pumps into the bucket) I always add a quart of Trans-Medic, Trans-X, or some other trans "healer" fluid. This will help swell the rubber seals inside the box and keep them flexible. Have done this on several 100K+ automatics and have put 10s of 1000s of miles on them afterward. I think the key has been adding the Trans-Medic to the new fluid. But, you shouldn't do a thing to this transmission - leave it as is. Since it's a Monte Carlo, with the engine revving away in 3rd gear on the freeway, you can pretend you're Dale Jr on the back straight at Talledaga (and be honest, that's really why you "bought" this car in the first place, isn't it?)
Mother's Day, I had the codes read or tried. AutoZone gave me error message and said to take it to a transmission shop. The code was Cooling Fan 2 failure. I haven't researched that one yet. So I'll take it to a trans shop where I think the owner will check it for free.