I have a '96 LSi with about 167,000 miles on it; I've owned it for the last 55,000 or so of those miles. And now I have a very worried look on my face because my tranny is failing to stay engaged in fourth on the freeway.
The Symptoms:
At steady speeds of 60-75 MPH in fourth gear (about 2000-2500 RPM), I've noticed two issues:
A. THE BIG ONE: While cruising along in D, the transmission disengages from fourth and starts a spontaneous, inappropriate downshift to third. The engine suddenly revs--and then, before third is fully engaged, the transmission slides back into fourth. For about a second it's not in either gear (sometimes it stays in third for half a second before upshifting again). This is starting to happen with extremely disconcerting frequency. I worry that this is Very Bad News.
B. THE LITTLE ONE: Even when the tranny remains in fourth gear, the RPMs jump up by about 200-300 RPM, stay there for a while and then fall back down; according to other threads I've found on this site (
41328 and
59909), the torque converter is unlocking and locking. No idea why the TC (TQ?) won't stay locked at cruise or what kind of problem that signifies.
The Context:
A couple of weeks ago I was halfway from Spokane to Seattle when I noticed my SVX leaving a trail of smoke behind me. Transmission fluid was dripping from all over underneath the car. At a gas station I bought Dexron III-labeled ATF ($3 or $4 a bottle), and pouring in a couple of quarts got my car the rest of the way to Seattle with no warning lights on the dash. A shop diagnosed and repaired the problem the next morning: one of the transmission fluid hoses had split at the radiator and was spraying fluid onto the engine. The shop cut about an inch off that hose and topped it off with another 4 quarts of transmission fluid.
So I was definitely running with low fluid for a while, perhaps some hundreds of miles. It's full now; the automatic transmission fluid dipstick is currently showing a hot level slightly (maybe 1/4") above the "High" dot.
I have not been good about changing my transmission fluid or filter(s), I'm afraid. Or differential fluid/oil.
The Research:
Similar problems have been reported here (threads
35574 and
59742), and someone else posted what sounds like my exact problem in thread
40291 and concluded it was probably the throttle position sensor (TPS); they didn't verify any solutions. But thread
35350 claimed some success from cleaning out the TPS.
Unfortunately because this is a '96 (OBD II) I don't have a way to read ECU or TCU codes or even to know whether any codes have been thrown (the CEL isn't on, at least).
The Questions:
1. If this might be a throttle position sensor (TPS) issue, should I try to clean it, repair it, replace it with a used one from a salvage yard (30-day warranty), or buy a new one?
2. If it's not the TPS, is my whole transmission totally hosed? Is the clutch for fourth gear (Drive) shot? A boatload of money to fix?
3. I suppose it would be a good idea to drain and replace the transmission and differential fluids and change the transmission filter (and buy new hoses connecting the trans to the radiator). It's about time for an oil change; should I have a Jiffy Lube also do those services, or would I be better off asking a repair shop to handle it?
3a. Does the '96 4EAT have an internal filter, an external filter, or both?
3b. Do I need synthetic ATF and/or diff oil/fluid?
3c. Should I replace anything else like the solenoids?
4. If I need to overhaul or replace the gearbox, I'd like to get a 4.44 (4.444?) final drive installed. I'm definitely not going to do it myself; any recommendations for getting that done in the Pacific Northwest?
The Promise:
When I find out what's wrong and fix it, I will report back here afterward so that others with similar symptoms can benefit and not have to guess what worked and what didn't!
Thanks.