new tranny, same problem..please help

[jasoninva]

The big question here is this...what other than a transmission can cause overdrive to malfunction and only work unpredictably.
I've got a 1995 Bonneville that has always had a tranny problem. When I first bought it, I soon noticed that I had to get in the upper 3000's before it would shift into overdrive. The problem got worse over 20 months. Just in the last few months, I had to do the following to get it into "OD". I had to get it up to 3900 while in "D", take my foot off the gas and quickly shift into "OD" manually. The tranny seemed to have an easier time getting into "OD" if my foot was off the gas at the time I made the shift. If I gassed it, the "OD" wouldn't engage half the time. Strange, but someone knows what this is. The tranny got worse and regular "D" sometimes wouldn't even engage.. I assumed that the tranny was going out soon so I had a used one with low miles installed. Cost me a total of $1200. I just got it back yesterday. Guess what…the problem was not solved.
The car still has the same “OD” issue, exactly the same. The other gears work fine now, but like the old tranny, there are times where overdrive just doesn't engage. Also, If It does shift into "OD" at say about 50/55, the rpms are only about 1200-1300 and the car feels bogged down and the acceleration is also noticably slow just after the shift. This may also be important. I came home from work yesterday and overdrive didn't engage. I got home, turned the car off and sat for 5 minutes, then took it back onto the highway. The overdrive worked just fine. IS IT ELECTRICAL? There are a few other issues with the car that may play a part in the problem. One issue is the RPM. The car idles at about 600-650. If I slow down and bring the car to a stop, the car has an initial idle of about 850-900 rpm. The car idles at this rate for about 15-30 seconds, then the idle just drops to 600-650. The car begins to shake and I feel like I’m being rocked forwards and backwards in the driver seat. At this point, the check engine light comes on. I took it to a mechanic a week ago and he replaced the upper/lower manifold gaskets. He determined that the manifold was sucking air so we replaced those gaskets. This did not fix the problem. Somewhere in the upper right corner where the manifold sits, there’s a leak. We just can’t seem to locate it . I hope these issues are all tied together somehow. The tranny model is a 4t60e if anybody wants to know.

[maxwedge]

Back up and post the year please.

[showshocka2k]

Originally Posted by maxwedge

Back up and post the year please.

he did, It's a 95...

[maxwedge]

Correct, I got lost in the text! Has your mechanic used a trans function scanner to check solenoid functions and slippage errors pertaining to the trans issue, the erratic idle can have many causes, bad tps ( can affect trans shift), vacuum leaks, missing o ring in the pcv valve, dirty throttle body and iac, these issues can only be solved with proper on site diagnosis.

[auto trainy]

Max,would a thermistat, temp sensor or related parts be a possible cause,just currious.

[jasoninva]

I've been reading this site for hours and hours. Remember the transmission itself is not the problem. It's brand new. I have found a lot of posts that seem to suggest these overdrive/check engine light issues could be tied to one cause, maybe one of these :
1. the computer(ECM)
2. the speed sensor..old moderator said "if its out of range the cruise control and TCC won't work"
3.the vacuum switch for the TCC lockup valve is leaking. Another guy called it the "TCC regulator valve".
4. simply a clogged fuel filter/fuel pressure issue
5. a bad TPS (throttle position sensor)
6 catalytic converter

[maxwedge]

If the engine/trans temp is too low the pcm blocks o/d, till the engine/trans temps reach a preset value..

[jasoninva]

I understand how low temps prevent overdrive from functioning. This is occuring while the car is running at optimal operating temps. I had been driving the car for a few hours before the drive home where it failed to engage overdrive.

[maxwedge]

You need to have it scanned with a trans function scanner to confirm the pcm is commanding o/d and underlying possible trans codes, as mentioned above.

[jasoninva]

I discovered that I am unable to get my codes read. Went to AutoZone and the scanner wouldn't work. My friend had the same model...didn't work either. Is my car too old? What's going on? Error code both times. Also, I've noticed that when at a stop, in drive or in park, when I press down on the brake pedal the rpms drop and the car begins to buck forwards and back. The car has been engaging overdrive, but last night it again failed to work coming home after driving for a few hours delivering. I hope this new info brings me closer to some kind of answer.

[maxwedge]

95 is obd 1.5 an requires a high scanner not AZ and as I stated a trans function scanner is required for proper diagnosis, most full line trans shops can do this. There is no " cheap" way around proper diagnostics for this issue.

[jasoninva]

had the codes pulled
740..."tcc circuit malfunction"...not fixed
171...fuel trim/lean...fixed this with new fuel filter
131...engine o2 sensor low(low voltage)...not sure what to do. Replaced the o2 sensor a year ago..the one around the engine that is ( there's a second sensor in the exhaust. I've been told this second one wouldn't affect performance)...

Took it to Bruce's Auto Parts(they installed the replacement tranny ). Scott Bruce refused to help. He got his money for the install and evidently could care less about customer satisfaction. Never ever use Bruce's Auto Parts in Mechanicsville, Va. He wouldn't even make a call to the company that sold me the tranny to let them know what was wrong with their transmission so the shop down the road from Bruce's i'm now using wouldn't be "seen" as making up problems for profits sake. I have a warranty on the tranny and this guy who installed it refuses to even call the supplier to let them know they sold a bad tranny. I am pissed!!!!

This code..740..
the transmission specialty book I got says that codes 39/740/1870 are "typically caused by a worn valve body bore or sleeve at the TCC regulator valve AND/OR isolator valve area."

[maxwedge]

Or a bad torque convertor.

[jasoninva]

Fixed it with a simple radiator flush. Can't believe this. I discovered the guy I used to have work on my car put 100% antifreeze in it about a month ago, just before I got the tranny put in. Guess what...100% antifreeze messes up the thermostats ability to read temp accurately. The thermostat wasn't opening soon enough, causing a constant heat issue. The heat prevented overdrive from engaging....some sort of tranny safety feature. Now overdrive works, but I think theres a bit more to do. I need to find out the acceptable temp range for the car. What is an acceptable range before the thermostat actuates?...mine seems to be at about 210

[jasoninva]

Well, i'm back to square one AGAIN!! Drove home after delivering pizzas for a few hours and overdrive would not lock up again. It worked fine for two full days...day one with the heater running the whole time to exhaust the heat and a second after flushing the radiator. But now i'm back to the drawing board. I'm noticing that overdrive has no problem engaging when the car runs at a proper temperature, but when it gets too hot..no overdrive. It seems to peak at 210-215 and it seems to stay at that temp for a bit longer than it should. I put my hand on the heat vent in the car and I swear it seems hotter than normal...feels like it could burn you if it was only a few more degrees. Wonder what the cars temp should be on a flat highway going about 65...under 200?..i swear i remember it always hanging just under 200 when i first bought it...who knows.I had the thermostat replaced over a year ago. I'll try a new one and i'll flush out the system again. I don't know what else I could do. Suggestions would be a big help. The fact the tcc locks up and stays solidly locked up when temps are good really makes me wonder if the torque converter/transmission is the issue. I thought the car had a safety feature that prevented overdrive from working if temps were too high....am I wrong about that? All in all, where should I go from here?