palliator Posted July 18, 2004 Report Share Posted July 18, 2004 I've posted this question on the old forums. I've asked several people. No one seems to have an answer. I have a 93 STS now with 44k miles. When I bought it there were some issues as the car just sat undriven for a long time. It took some work to get it be a reliable daily driver, but now for nearly a year it has been running perfect. The only remaining problem I have is when the transmission shifts gears, though whether it is actually a problem or not is debatable. Sometimes it shifts so smoothly I can hardly detect them. Other times the first two shifts feel a little rough and you can definately feel a "bump". During my driving it doesn't seem to matter if that particular day I had a lead foot or not, it just seems very random. I thought perhaps the harder shifting was due to more aggressive driving, but I am not so sure. Maybe its just me, but overall excelleration seems smoother during when I hardly feel the shifts and the tach stays held at a certain RPM before making the shifts. During the rough periods the transmission doesn't hold at any RPMs and quickly shifts to the next gear at whatever RPM the shift point is set at (I only detect the first two shifts). Everyone out there with the same car, how smooth do your shifts feel? On normal take offs at the light, at what RPM is the first shift point? I have no trouble codes, no apparent hesitation in shifting, no excessive RPM loss, and slippage. The trans fluid was just changed and I checked around a bit to see if any problems (shift solenoids, foreigns materials/objects in lower pan, burning smell, etc). and every looks perfect. I thought it was the speed sensor in the transmission, but I thought that would trigger an error and I get nothing. Code history never showed anything related and has been cleared since I fixed everything. The only issue issue I had that could possibly related was a stuck brake switch, but I fixed that (TCC now engages). It just surprises me that shifts are sometime rough and so noticeable on a luxury car, I don't mind them and can live with it but I worry that something could be wrong. Any input would be greatly appreciated. Link to comment Share on other sites More sharing options...
franey Posted July 18, 2004 Report Share Posted July 18, 2004 First all gm transmissions are designed for soft shifts, this is what the driving public wants. If you have a transmission rebuilt , the builder will sometimes turn up the line pressure to give a SLIGHT BUMP when it engages.THEY do this so the gears will go quickly and solidly together, this of course is an individual builders preference . In years past i have taked several back to the shop for them to turn down the pressure for a smoother shift. In your case your car has sat around a bit, and probably has varnish built up in the valve body which will somtimes cause the parts to not work properly , giving it the occasional hard shift. TAKE it to a reputable transmission shop and have them remove the valve body and clean it and i bet your problem, will be over. Removal of the valve body is not a rebuild and as such should be priced accordingly. Link to comment Share on other sites More sharing options...
CaddyShack24 Posted July 18, 2004 Report Share Posted July 18, 2004 Please respond back on this issue.. My 1993 STS also sat many years and I have this same condition(as do about 7 others on here) .. I'll go check the RPM of the upshift. Link to comment Share on other sites More sharing options...
palliator Posted July 19, 2004 Author Report Share Posted July 19, 2004 Thanks for the reply. I wondered why it seems to happen randomly, the heavy shifts characterized with the "bump". Again, sometimes the shifts are unnoticeable. It seems when the transmission is required to do an agressive shift at any point, from that point on the transmission stays shifting hard (if that makes sense). I've given up on finding a pattern. If I'm not wrecking my transmission by driving it this way, I can live with it. It's not a new car, but it's annoying to have this flaw in an otherwise perfect car. I have a local transmission shop down the road that is so close I could walk there in a few short minutes. Maybe I will try them out and see what they say. I refuse to take it to the Cadillac dealer. I live in the Toledo, OH area. Frankly I am weary to take it anywhere as transmission repairs can mean big $$$, whether necessary or not. It's too bad I can't do something about it myself. I've dropped the lower valve body on a 4T80E before to do solenoid replacements. I wouldn't attempt to do much more than that, like attempting to replace the speed sensor. I know my limits... Link to comment Share on other sites More sharing options...
franey Posted July 20, 2004 Report Share Posted July 20, 2004 Take it to the shop, as you know the valve body is on the bottom, tell them you just want them to take it out give it a good bath new gaskets where necessary, new filter change ALL of the fluid that will drain out , check the wireing and put it back together. Tell them why you want it done and you fully realize you may still have the problem once they are through but you wanted to give it a shot ,and are not looking for a rebuild. If it is an honest shop , they will be happy to do it. IF they start all the crap about it being a cad and special trans. and you have to walk on water to service it, find another shop. Link to comment Share on other sites More sharing options...
CaddyShack24 Posted July 20, 2004 Report Share Posted July 20, 2004 How can it be the transmission if it only acts up on occasion? Has to be an electrical type thing. About the RPM, my traction disabled / Service ride control is on.. so im starting off in 2nd gear, that'd do you know good really -- its in the mid to lower 2k range though. I feel that the bump is from a faulty TP sensor.. giving the wrong reading and then the transmission engages the next band, causing it to jerk. But, tonight I had flawless shifts.. when expecting the 'bump' .. it sounded like the tranny was slipping, first time i've heard this.(but shifted very smoothly) Link to comment Share on other sites More sharing options...
pos2nat Posted July 20, 2004 Report Share Posted July 20, 2004 When I first started to run my 93 a little harder...5500-6000 rpm shifts, I experienced the same hard shifts in traffic with the Service Engine light coming on. I would clear the code, I honestly cannot remember which one, or stop the car, shut it off and restart, and the trans would shift normal. Then after getting confidence that this babe can withstand it, I really started to use more WOT, letting the trans upshift on its own at 6500, 6700 rpm on open stretches of hway or on ramps....at least once a night M-F going home from work. The problem disappeared after that. I have not seen that light in over six months. In regular driving and traffic, I try to keep my shifts near 4000 rpm, when possible for max torque, I think I get my best fuel economy then. My only beef is I hear a whine from either the trans, or one of the accessories or water pump when I drive my car over 4000 rpm, just before the trans shift and the car is not warmed up. After the coolant temp reaches 196, the whine disappears. Link to comment Share on other sites More sharing options...
franey Posted July 20, 2004 Report Share Posted July 20, 2004 Transmissions have similar problems, but the cause is not always similar. When a car sits the most common problem is varnish, not wireing, although your problem may be wiring. Why does one transmission go out at 90k and one is still running at 220k. Friend of mine 435k on chev. truck . NEVER has changed fluid or touched transmission. WHy does the guy who does all maintainence and babys his car have a new transmission at 60 k , guy who does nothing but WOT ever time he takes off replaces his at 170k . Weak parts , AB SELINOIDS, AND OTHER INSIDE WEAK PARTS FROM the get go, are common to all of the transmissions, when yours goes who knows. THE first guy may only need to have his valve body cleaned, you may need wiring harness. You may have a crack somewhere inside that under certain conditions lets to much line pressure blead off, causing poor shift or no shift . You could have the whole thing rebuilt and still have the same problem , would not be the first time it happened. I hate to say this but the best thing on transmissions , is FIND A GOOD AND RELIABLE SHOP , that is familiar with the transmission , and they have a good diagnose person , on board , you can be a good builder and not know anything about diagnosing a problem . Another sad thing is their is becoming a shortage of good transmission people, no new brite blood entering ther field for the amount of work on the horizon. Dealer only one with trained people on , ever changing transmissions. GOOD LUCK TO ALL Link to comment Share on other sites More sharing options...
palliator Posted July 22, 2004 Author Report Share Posted July 22, 2004 I think I am just going to give up and take it to the shop. I know some of you have been saying that all along to find a reputable shop, but I wanted to attempt to nail down the problem beforehand. There's always the Caddie dealer... It looks like there are too many factors that could be the cause, especially since it happens randomly. I hate not having an idea when I bring it into shop, mainly because I don't want to feel like I am being suckered when they tell me how expensive the repairs are going to be. FYI, a couple of days ago I floored the car while at about 30 mph. It downshifted and hit about 6000 RPM before shifting. At this speed, the shift felt normal. I let off when I realized I was approaching 80 mph. Shifts afterwards felt pretty normal. So, again I have no pattern to the erratic behavior of the shifting. I give up. One last question, is it normal to have a slight "whistle" or high pitched "hum" when you shift into drive? I emphasize that it is not very loud and may be normal, but I do notice it when I have the windows rolled down. I would like to know if this is normal or not? Link to comment Share on other sites More sharing options...
rmac-etc Posted July 22, 2004 Report Share Posted July 22, 2004 I don't think any kind of whistle or hum should be detectable as a result of a gear change of any kind. I am not an expert on this, but that suggests a simple vacuum leak. In a few years on this board I do not remember any vacuum related issues, but I could have missed that one. Link to comment Share on other sites More sharing options...
CaddyShack24 Posted August 5, 2004 Report Share Posted August 5, 2004 Did you find out anything? Nothing here.. i noticed that when i manually shift from 1st to 2nd. its horrible. I'll do a real through test sometime.. id do it tonight but my battery is dead and nobody around. I'm scared, hold me. Shifts occur around the 2.2 rpm range. run it higher and it minimizses the effect. not as noticable from a cold start. backing off the throttle minimizses the effect. Fluids were changed not even 10k ago. Link to comment Share on other sites More sharing options...
bigfoo Posted August 5, 2004 Report Share Posted August 5, 2004 Change the fluid and subsitite a quart or two with lucas tranny fix stuff.. It solves most problems with older transmissions as long as something isn't broken. I'd also clean the filters if you feel like removing the pan. It's a cheap solition to try Link to comment Share on other sites More sharing options...
67coupedeville Posted August 6, 2004 Report Share Posted August 6, 2004 Thats a BIG 10-4 on the Lucas Transmission Additive good buddy, real good stuff! Spence Link to comment Share on other sites More sharing options...
bigfoo Posted August 6, 2004 Report Share Posted August 6, 2004 HGehe.. I ALWAYS give that a shot before doing anything else. Lucas makes some good 'stuff' :> It's like marvel mystery oil.. not many people know about it, but it rocks :> Link to comment Share on other sites More sharing options...
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