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Pontiac Bonneville Transmisssion

Yeah i just bought a 1999 bonnevile SLE when i first got it the transmission was basicly ruind. My fourth gear was pretty much destroyed. So the dealership replaced it and now its shifting hard and hesitating when shifting into 2nd and 3rd, and bogs down when im going around 30 MPH. People keep telling me to let in get broken in cause its knew but i dont know.


  • Hey, you probably had this fixed by now, but I had a 99 Bonneville that needed a transmission at 108,000 miles. It broke my heart to spring for it, but that was the only repair that car EVER needed that wasn't maintenance. I would find a transmission mechanic that is certified (ATM or ATD, can't recall what they're called) and get another opinion. You shouldn't have to break it in. Mine was guaranteed for 10k or 1 year. Unfortunately, my 7 years was up on my GM card so I traded it. Big mistake. 06 Impala is a huge disappointment. (6 times in garage in 4 months). I'm looking for a B-ville on ebay now. Does anyone out there know the reliability of 04 and 05 Bonnevilles? I was warned not to buy any 00-03 models. Thankx.
  • No its still acting up, and my fuel line as bursted twice. Its in the shop right now, and i got some seafoam for my tranny, so ill see what happens.Also ive heard that on the 00-03 bonnevilles have problems with the gauge cluster with the lights going out, and the cd player sometimes goes into lock mode for no reason.
  • my girlfriend has a 95 bonneville with a bad tranny and i found a tranny thats in a 93 bonneville for a pretty good price at a local junkyard that comes with a 30 day warranty. I know or at least ive been told that the tranny itself is the same, wut i need to know is if the plugs for the wire harness is the same. so basically wut i need 2 know is will the tranny out of the 93 work and is compatible with the 95. if anyone could help answer this question for me i would greatly appreciate it. thanks
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    Send me an email at the address you read in my profile. Click on my name at top of this post. I can possibly direct you to people who will know. I assume you know the transmission is definitely bad; some engine problems can make somebody think it's transmission problems.

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  • Ya the wireing harness will work with the 95 bonneville, the 95 and the 93 transmissions are exactly the same.
  • benny17benny17 Posts: 5
    I have a 99 bonneville sle and i was wondering if i could change the tranny with a 99 ssei transmission, or would this cause problems?
  • car runs good but sometimes it seems like it gets stuck between overdrive and third and sometimes about 65-70 it will kind of loose power and vibrate, you let off the gas or push it down further it quits for a while mostly on inclines
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    How many miles on the car?
    When were the spark plugs changed last?
    When were the spark plugs wires changed last time?

    My suspicion is that it's the plug wires or the plugs. It probably is lugging at a low RPM in 4th on a slight incline and you accelerate slightly and it's misfiring. Try driving the same circumstance or place with the car in 3 instead of 4. That will keep the motor turning faster and you won't notice the slight misfire.

    Or you can do the incline at a lower speed in 3rd at th same RPM and it probably won't do it because in third the load on the motor won't be as great on the same incline because of the lower gearing.

    It might be a transmission probably but I doubt it.

    You can go to one of the auto parts stores that does free scans for codes on your car and you'll probably have a code for misfiring and it may give a particular cylinder on which it occurs or it may be random misfire. Advance Auto does it in this area. Even though the check engine light is not on there may be a code. If it gets worse the code might cause the light to turn on.

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  • Hello all, when I accelerate quickly from a dead stop my transmission, or at least my front wheels chatter or maybe a better description would be the feeling of ratcheting. this ratcheting can be scribed as on the verge of violent, once again this only occurs from a dead stop. No other anomalies are noted at any other speeds or shift points.
    The year is 1999 with around 140,000 miles.
  • I have a 96 Bonneville SSEI that sometimes while driving it feels like it is stuck in 2nd gear. If I turn the car off and then back on it sometimes shifts fine then, first thru overdrive. Could that be transmission modulator valve or transmission control solenoid? Tranny was flushed and new filtered in December. Also, were is transmission control solenoid located.
    One day it shifts fine and the next day it may not.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    >Tranny was flushed and new filtered in December.

    Do you mean it had one of those flushes where they connect hoses and supposedly change all the fluid without dropping the oil pan and replacing the filter?
    If so, did they put in an additive?

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  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    >wheels chatter or maybe a better description would be the feeling of ratcheting. this ratcheting can be scribed as on the verge of violent

    Does it seem like the firewall under the windshield is jumping up and down? That may mean that a certain part, I believe a Sprague (spelling?) is slipping. Try using 1st gear and see if the same thing happens. I'd recommend against accelerating hard enough to cause that to happen. It may be reduced pressures in the transmission due to wear on the pump. It may be pressure control valve; some of those have had problems. Your transmission has 140K miles and that's good.

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  • My 95 Bonneville will run down the hiway for about 15 minutes in overdrive, and will, on its own,shift back into drive, and will not return into overdrive unless I stop for fuel or to let it cool. When I resume the trip it will work fine for about 15 mins. and then do the same thing again, every time. Can anyone help me determine the cause of this problem? Thank you.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    Is your motor overheating? I believe it turns off the lockup torque converter and may shift down into 3rd if that occurs. That spins the motor faster, circulating water faster, and cools down.

    Are you running too cool. Without checking a 93 manual and 98 that I have, I believe it won't shift into 4th under the coolant reaches a certain temperature on a cold startup. The obvious reason is pollution control and running faster which heats up the coolant faster decreasing pollution. IF your thermostat is opening too much the motor may be cooling too low and the PCM is doing what it is supposed to do.

    I suggest these fairly innocuous reasons it may be doing things strangely, because you haven't said anything about shift quality being back. Late, early, rough upshifts. Strange shifting while cold or coming to a stop aren't mentioned.

    If your car has a temperature gauge, follow it to see if things are acting normally. If the thermostat hasn't been changed in a few years, that would be my first suspect.

    Are you in a cold climate?

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  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    Is your transmission fluid low? That was mentioned in the service manual for the 4T65E transmission. I believe you have the 4T60E. I'll check that manual later when I find it.

    Another factor might be the temperature of the fluid is going high and the transmission downshifts out of overdrive.

    Are the other three speeds all working completely normally? Can you feel the transmission go into 4th and then the lockup torque converter latch in which reduces engine rpms more?--when the trans operates normally.

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  • The problem started a few years back while pulling a small trailer, and only happened while pulling the trailer. But of course has worsened to where it happens without the trailer.The rad. was removed and boiled out, and the fins cleaned. The Therm. has been replaced a couple of times. It shifts fine, and predictable. As far as I can determine this trans is not electronically controlled. However, it apparently has two sol. valves, one for the 1-2 shift, and one for the 3-4 shift. Plus another for the lockup. On the older and smaller 125 series trans, the lockup sol. gave trouble holding the converter in a locked position, and not locking up at all, and needed to be replaced. Could this be the problem here? I can't tell if the trans. is running too warm. If it is, it is not bringing up the coolant temp. The coolant temp runs a consistent 190-195.
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,707
    The small trailer probably should have been towed in 3 where the higher ratio would have allowed an easier tow and the fluid would have stayed cooler.

    Or an external cooler can be put in the trans fluid line after the fluid goes though the radiator and keeps the fluid cooler.

    The neighbor had towed a boat with his Blazer in 4th gear without a cooler once a year to the Lakes area in Southern Kentucky--mostly interstate, and hurt his transmission with overheating.

    I believe you have a 4T60E which means electronic controls. But diagnosis is needed.
    Has it had a filter change in the last 30-40 K miles? I hope it's something simple like a solenoid for the torque convert lockup.

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  • Yes, the firewall does seem to jump. I will try using 1st. gear this morning to see if it makes a difference and I have been trying to baby the acceleration. Thanks
  • Yes, you are right on using the lower gear to pull a trailer of any size! I'll have to check the records for the oil and filter change. It is a 4T60E, but is there a separate module that manages the transmission, of is it managed through the ECM? You mentioned diagnosis, is it possible to pull a code tor this kind of problem? Thank you for the help.
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