Okay. This might seem long but I want to provide some details to hopefully get a better understanding of my situation.

I have a very well kept 1992 Pontiac Bonneville SE (I believe it has the 4T60E trans??) with 67,100 original miles on it. The car belonged to an elderly uncle of mine who passed away and it was left to me when it had something ike 30,500 on it back in May 2000. Since that time I've been strictly keeping up with all the basic maintenance and repairs like oil changes, air filters, new tires, radiator flushing and new hoses, new brakes and rotors, belt replacement, new alternator, new water pump, new plugs and wires, muffler, PCV valve, and added a transmission cooler. One thing I plan on doing soon is the fuel filter since I'm not sure if it'* ever been changed...

In 2002 the transmission began to act up: Besides hearing and feeling a quick sound of chriping coming from somewhere around the front-end whenever I drive around 30-45 MPH that comes and goes depending on if I speed up or slow down, whenever I drove the car and began to slow down after turning off and onto an exit or just slowing down to stop for a a red light, it would buck or hesitate a little coming to a stop and sometimes it felt like it didn't want to move after giving it gas (like it was in neutral). So the trans fluid and filter were finally changed (51,300 miles) and replaced for the first time that I know of, or at least while I've had the car. Oddly enough, that routine bit of maintenace stopped the problem entirely until I did something that probably didn't need to be done.

A few months ago, in August before going on vacation, for some stupid reason that doesn't make sense to me know that I'm having a problem, I figured it was perhaps time to change and replace the transmission fluid and filter again since it'* been three years since the last one and since I had an extra filter and fluid. A neighbor who once worked for AAMCO Transmission gave me a case of their "synthetic blend" transmission fluid that could be used in applications wherever recent various Dexron type fluids were required for certain transmissions. Well I used the stuff and everything seemed fine until around September (actually about two weeks later) when I was getting that "bucking" hesitation again whenever I came to a stop - not bad, but again after slowing dow from highway driving. It didn't happen a lot but it was certainly noticeable whenever it did happen, which wasn't that often.

Well this week the transmission has really begun to act up like it had back in 2002. Today after hitting traffic on a highway, I came to a stop and the car felt like it was suddenly in neutral...For a second or two when I put my foot on the gas (just to move along with the traffic) I got no movement at all...then, all of the sudden, that familiar "bang" or hard thump that felt like someone tapped me from behind before the guitar finally went into gear. A few minutes later, when stopping at a station for gas, the hesitation was subtle and not as obvious but never the less was still there. Again, as in the past, I also checked the fluid level and it was at the proper level as always.

One of my questions is this: Has anyone else encountered this type of problem?

I realize the transmisison has to be checked out (which I'm having done tomorrow) but could it be that a transmission fluid with any type of synthetic involved can possibly cause this type of problem? I've heard that sometimes whenever synthetics are used in some transmissions that simply don't really require or need it, it'* just too slippery and not advisable because it can cause problems where regular fluid wouldn't.. And would it just be better to continue using regular fluid now and after whatever problem I have is fixed?

Sorry for this long post...Just wanted to get some feedback.

yes you are correct from what everyone here has said, synthetic is not a good thing for our tranny'*. don(jr3800) will kick in soon with some answer for ya, as he knows alot about our tranny'*.

Devon

Thanks Devon. I'll be checking back regularly to see what others can add...I've done a thorough search here on the Bonneville forum and have read a lot of the past posts on GM transmission horrors... Finally, now, I have the misfurtue of being yet another name added to that long "infamous" tranny problem list. :(

im still on the original tranny, *knocks on wood* altho i went through 3 transmissions in my 90 SSE in 115k miles

Though it'* a very basic 1992 SE, the fact of the matter is that if this car wasn't in the solid conditon that it'* in, if it didn't cost me any money to obtain to begin with, if it didn't have the mileage that it has on it, and since it never had any really major costly problem that could not easily be fixed, I wouldn't even be asking these questions...It would have been gone already.

Not only that, but I realize that could have paid big bucks for a new car and had transmission problems not long after driving it off the lot, which happened to me in the early '80s three months after I bought a brand new Oldmobile 98 Regency Coupe (which was under warranty but still burned my *** to no end). So in a way, if it'* taken this long for something really major to happen, then there'* nothing I can do about it since I know I've taken care of the car as best I could during the time I've had it.

But right now, a new car payment isn't something I (like many others) want in my life since my wife and I are about to buy a new "family" car within the next few months. And even though this is a 1992, this car is comfortable and has always been an enjoyable drive and a pretty much dependable ride. I never even thought about dumping it, even though this re-occuring probelm has really put a bug up my *** as it certainly has for others who've experienced similar or even far worse tranny problems.

mine has a getting worse issue with shuddering problems with the TCC not locking up-all the way (or so it seems), also clicks when going into reverse...sometimes it has a decent lag before hitting 3rd gear (like it pops in neutral when accelerating at low rpms) and I am failry certain if not positive it is not ignition related since I have replaced a vast majority of the ignition parts

Let'* start with the basics that you have probably already covered.

Fluid level been checked?
Does the fluid look odd or different than standard red and good smelling?

Certainly it is worth trying some conditioner or another filter and fluid change. However since you are bringing it to a shop today, let'* hold off and see what they say.

Lets see...The transmission fluid level has been checked and monitored on a regular basis and appears to be fine. Also, the fluid color is as red as the day it was poured from the bottles about four months ago and has no out of the ordinary burning smell to it. Incidentally, the fluid I used was labeled AAMCO MERCON V which can be used for cars requiring some recent Dexron fluids as well, according to the information printed on the bottles.

I forgot to also mention, though I'm not sure if it would contribute to my current problem though, is that (1) Lucas brand transmission additive was also included in that last fluid and filter change back in August...(2) The transmission does shift and runs good as far as I can tell - that is until I begin to slow down, stop, and then begin to drive again. It'* during that procedure that things begin to get "uncomfortable."

As I said before, I'm dropping the car off later this afternoon and leaving it at the shop for however long it takes in order to let the mechanics drive the car around in order to experience the problem for themselves.

Sounds like the torque converter. I wonder if the first fluid change helped prolong it and that it'* finally starting to have issues visible again.

BillBoost:

I know little to nothing about transmissions and torque convertors so please excuse my ignorance...When problems are a result of the torque covertor, does the existing convertor get overhauled or rebuilt (if that'* even possible) or is a new convertor usually installed?

And what about the rest of the transmission? I mean, can the existing transmission actually be in good shape even though the torque convertor is the source of such problems?

I genuinely appreciate the information you and anyone else has shared with me...Seems like my situation it is not all that uncommon for people who own Bonnevilles and other similar GM model cars with similar transmissions. Thanks!