Trans won't go into overdrive [Archive] - GrandAmGT.com Forum

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IanGT99
12-16-2009, 11:33 AM
Hey all. Searched for a solution, but to no avail. 99GAGT with 138,000 miles. I've noticed over the past few months that my tranny is acting weird and it's getting worse with the colder weather. When I do a cold start and begin driving, it takes the tranny about 5-10 minutes (or until the car is fully warmed up) for it to shift into overdrive. It surges very slightly, seems like it loses power for a split second, then everything seems to work ok. The revs are a little lower than normal, too. I cruise on a flat road at 65mph at about 1900-2000 RPM. It's usually around 2200. I don't hear any misfires and the tranny doesn't slip. It just shifts at odd times. I just threw an SES light yesterday that I'm going to get checked at Autozone on my way home, so it's starting to worry me. I changed my spark plugs in September, but didn't change out the wires. I have Tayler Spiro Pro 8mm wires that still look fine. They do have a decent amount of miles on them, though. Does this sound like a plug wire issue or something else?

cardude007617
12-16-2009, 01:27 PM
the trans won't shift into overdrive until the fluid gets warm enough... or did i read this wrong

IanGT99
12-16-2009, 05:29 PM
No, I understand it won't until it gets warm, but it seems to be taking much longer now and shifting harder into overdrive. I had a coolant flush/fill done and replaced my 180 degree stat with a stock one (I was getting tired of never being warm in the car in the winter). The car heats up quicker and gets hotter than it did when I had the 180 stat, but it seems to be taking longer to shift. And like I said, it surges, looses power for a split second, and then slightly jerks into overdrive. I don't know what I could do other than change out the wires. Maybe one or a few of them aren't making good contact anymore. The tranny fluid is only 30k miles old, so I still have at least half of the usable life of the fluid. I'm puzzled...

AaronGTR
12-16-2009, 06:10 PM
Technically there is no overdrive. There are just four gears, and it should always shift into fourth at a certain speed and throttle position, regardless of temperature. It does not need to warm up before it will shift into fourth. I would say you need to be sure what gear it is really in first, with a scanner while driving. 2000rpm at 65mph sounds like a pretty normal rpm for fourth gear to me. I usually sit at 2200 at 75mph on the freeway.

IanGT99
12-17-2009, 11:16 AM
Well, it's almost like I'm in a different RPM range when the car is cold. Like it's in 3rd and then all of a sudden shifts into 4th. At 65mph when the car is cold, I'll cruise at about 2400 then when it finally warms up and shifts into 4th, it quickly drops to about 1700 or so then evens out to 1800-1900 or so. I don't know what it could be, but it's worse in the colder weather. I know I should expect it with an 11 year old car, but I've done strict maintenance on it and kept it up well. I just need it to last a little longer...

Tank33
12-17-2009, 12:10 PM
I am having the same problem.

at about 55 MPH the car goes to kick into it's final gear, it makes the shift, and then it surges in and out of that gear, jumping in 2- 300 RPM increments. Sometimes it is there, others it is not, seems to depend directly on the cold from what I have seen.

Has me stumped and it's ticking me off, I only have 103,000 KM on mine and it is an 04!

IanGT99
12-17-2009, 08:35 PM
Yeah, I noticed a little bit of surging in mine too, but not too bad. It just feels like it shouldn't be happening.

IanGT99
01-25-2010, 11:24 AM
Found and fixed my shifting problem. From a cold start, it would take my car about 5-7 min. of driving to actually shift into 4th and get into the lower cruising RPM's. It would ride in 3rd at about 24-2500 RPM and then all of a sudden drop down into 4th to about 1800 RPM after warming up enough. The car was shifting a little harder than it normally did and the problem just kept getting worse. As I was changing my oil, cleaning the intake system, and doing some regular maintenance this weekend, I checked my spark plug wires. I had Taylor Spiro Pro 8mm wires that were pretty old and had a lot of miles on them. Turns out the boot on top of the coil going to my #4 cylinder was rusted. I used dielectric grease on the boots, so I didn't quite understand this. I guess I didn't coat that one well enough. Anyways, I went directly to Autozone and picked up a set of Bosch 7mm wires. After I put those on, everything smoothed out, the car ran better (fresh oil helps, too), and it just felt more responsive. Even from a dead cold start, the car shifted into all gears smoothly and seemlessly. It's only been two days and two cold starts that I've noticed this, so I'm hoping it lasts. For the time being, it seems everything is great. It's amazing how some of the biggest problems are caused by the smallest things. Thanks for all of you guy's help.

Saber326
01-29-2010, 03:36 PM
if the problem persists, my first guess would be the torque converter lockup.

IanGT99
01-30-2010, 11:26 PM
After a little over a week of driving, it still takes a bit of warming up for it to actually shift into 4th, but it's a MUCH less pronounced jerk into gear. It just goes down into a little lower RPM. The car does shift better and more smoothly in general, too. I'm very happy with how it's been behaving. I just need the ol' girl to last me about another year.

skifreak122
01-30-2010, 11:56 PM
Are you sure that it's shifting into 4th after warming up instead of the torque converter locking up? From what I understand the converter wont lockup until the tranny fluid has reached a certain temp. At that point (usually when you're car reaches operating temp in very cold weather) the converter will lockup and your rpm will drop down to a normal cruising level.

IanGT99
02-01-2010, 11:11 AM
^^^ Honestly, I'm not sure. I'm almost positive it's not going into 4th until it warms up, but I'll certainly pay a lot more close attention to it when I leave work tonight. That definitely sounds like it could be what's happening. My fluid and filter are only 30k miles old, but that could be the problem. I think I'm gonna have them changed here shortly to see if it helps. Is there anything else I can do to fix this problem without a major trans overhaul?