shifting problems???

Hey, mostly when I'm driving my car shifts kinda hard when changing gears. Its really annoying. Sometimes its hard and sometimes its not. Also when I put my car in reverse from park after its been sitting a long time like overnight it has a loud bang like a drive over something. But if I start my car idle for 1-2 min then I dont hear the loud bang. Can u tell me whats wrong with my car. I have a 2002 Grand Prix GT with 87K

Normally hard shifting is a pressure control/line pressure issue. Get it scanned and see if any tranny codes are stored in history. When was the last tranny service - ATF and screen filter?

I only had the car for about 2 years and I've never done any transmission service to it.

Start there. It is due anyways. 100K mile service. Do not flush. Just a pan drop service only replacing the screen filter and fluid. About 7.5 qts. You can use Dexron III or the new Dexron VI ATF.

I was told if I do a transmission fluid change too early it would mess up the transmission and make it worse.

Not necessarily. It can't be any worse than it already is.

Start there. It is due anyways. 100K mile service. Do not flush. Just a pan drop service only replacing the screen filter and fluid. About 7.5 qts. You can use Dexron III or the new Dexron VI ATF.

Bob, why don't you want to flush the fluid, out of curiousity?
drob99, when I got my GTP, it had 68K on it (at 122K now) and I've done a tranny service every 25K, and the transmission is as smooth as butter. I highly recommend that you make a tranny service a regular part of your maintenance routine.

Bob, why don't you want to flush the fluid, out of curiousity?


Good question. It is an old issue we have covered over and over through the years here at this forum. Just to make it short just reference our old threads on the subject. Here's a good one and the best explanation I think I have ever provided is at post # 7.

http://www.automotiveforums.com/vbulletin/showthread.php?t=554204&highlight=power+flush

Other than a general concensus in this forum probably not. There have been a lot of horror stories. Some had success with flushes. But first the data should be split or differentiated between what type of flush are we referring to? Technically there are two types performed or even recommended by GM. There are different flush fixtures used by GM dealers, trans shops and the fast lube places. GM only recommends two specific types.

They recommend one brand of fluid exchanger (Wynn Transerve) and one brand of flusher (Kent-Moore). Then on the flushing it was recommended only if there was a transmission failure or problem, otherwise not for routine maintenance. Also, GM only recommends a certain approved flushing detergent to encapsulate fine particles which is used with the real flush machine. The fluid exchanger which is technically not a flusher will not remove particles because it is low pressure and uses the tranny's pump.

I believe the bottom line is this, GM only recommends flushing if there is a problem, otherwise they only recommend a fluid exchange using the Wynn Transerve or similar probably to get all ATF out to include in the torque convertor which is really only for convenience and ease of maintenance.

Most of the flushes ever mentioned are not real flushes but fluid exchange. The fluid exchange doesn't sound too kosher to me and IMO a pan drop consisting of replacing at least 7.5 quarts of the ATF and screen filter is better for obvious reasons.

Wow! Thanks for the info!

Wow! Thanks for the info!

You're welcome. So whats the verdict? :lol:

You're welcome. So whats the verdict? :lol:

Do you mean which do I agree with (flushing or not flushing)?

Do you mean which do I agree with (flushing or not flushing)?

I made it easy for everyone. This thread is now a poll.

no flushy flushy

I read that thread and there was wealth of what's, but I didn't quite catch the why's. Someone mentioned that doing a true flush can "shock" the system. Why is that? If we had some variety of bio-transmissions I could follow that, but I'm not following what damage occurs by flushing? I'm not saying I'm disagreeing with anyone, I'm just trying to get my mind around the whole concept. :screwy:

It depends on what flush we are talking about. The real power flush done by the dealers or even transmissions shops is intended for malfunction not as preventive maintenance. If you check the GM factory service manual for our GPs there is no mention of flushing the transaxle. The fluid exchange service is really not a flush but replacement of just about all ATF in the system which includes the lines to the radiator and whats left in the torque converter but the screen filter is not replaced during the process. More of a money making deal for the quick lube places and even dealers. I've never had any of my GM cars flushed. Just a pan drop service and screen filter. Plus it is cheaper.

I used to work at an oil change place (bad career move there let me tell you...) and any customer that wanted a trans flush with a vehicle that had over 80k miles had to sign a waiver that we were not responsible for any later transmission damage. That right there is enough to tell me it's a bad idea.

As Bob stated, the quicky lube trans flush/fluid exchange machines use the vehicle's trans pump to move the fluid. Therefore, any claims that they "back flush" the filter is total BS. Also, if the operator isn't paying attention and doesn't have the valves on the machine adjusted properly, it can either run the car's pan dry or overfill it causing damage to the trans. I have seen many instances where shortly after doing a flush, the trans takes a dump, where I've never seen it when a pan drop/filter change is done. The reasons vary, but the results don't lie. As I've stated before on this topic, if you wait until the trans fluid is burnt and you NEED a flush, it's too late and the flush will not help.

So if a "real" flush were to be done, there would be no need to drop the pan, correct? Everything would be done through the machine?

We have had ZERO failures from trans flushing. 90% of people want a trans flush when something is wrong other than that it’s out a sight out of mind. There are very few people that do P.M. most run until an issue arises then think the service or flush will be a cure all. Now keep in mind we do NOT have a flushing machine and always pull the pan first (if there is one) and if we see a problem we stop there. Another thing to avoid is the quick lube places for trans maintenance!!!.

This is not really a reply, but a question in it's self. My brother has the shifting problem. He already ran the codes check and come up with the speed sensor. I heard that 2 speed sensors on this car. Since the car mostly acts up when it is raining, we figure that it is probably the speed sensor outside of the transmission. I was wondering if anybody could tell me where this other speed sensor is at, it would be greatly appreciated.

Another thing to avoid is the quick lube places for trans maintenance!!!.

Along those same lines, avoid going to a steak house for heart surgery. :nono:

This is not really a reply, but a question in it's self. My brother has the shifting problem. He already ran the codes check and come up with the speed sensor. I heard that 2 speed sensors on this car. Since the car mostly acts up when it is raining, we figure that it is probably the speed sensor outside of the transmission. I was wondering if anybody could tell me where this other speed sensor is at, it would be greatly appreciated.

There is an input speed sensor (ISS) which is hard to get at. Located at the the area where the torque converter is located at the input shaft of the transaxle.

And welcome to AF.

I'm not a flushy person myself, so I would say no to a flush. I have heard horror stories from people who have flushed, and myself feel that if the trans fluid is changed regularily (ie pan drop) that a flush would be a wast of time.

I have however flushed tranny coolers as a process after a complete trans rebuild. No issues there.

While we are on the topic of tranny's, what do you guys thing of this?....
I'm thinking about getting one for when I do my next pan drop. I like the idea of keeping the trans cooler, plus it has a drain plug for future fluid changes.

http://www.zzperformance.com/grand_prix/products1.php?id=547&catid=105

While we are on the topic of tranny's, what do you guys thing of this?....
I'm thinking about getting one for when I do my next pan drop. I like the idea of keeping the trans cooler, plus it has a drain plug for future fluid changes.

http://www.zzperformance.com/grand_prix/products1.php?id=547&catid=105

Waste of money Tim. The best aftermarket pan around was the one by MSP which is no longer available. It allowed for an extra 1/2 qt of ATF capacity. Plus you can add a drain plug to the stock pan. Unless tranny temps are an issue save your money. A tranny oil cooler would be more effective.

Good to know Bob!. Thanks for the advice!

Tranny temps aren't an issue, and I think if I install an external cooler that it might have reverse effects during the wintertime. Just was looking into it.

I will keep my eyes open for a used MSP, and look into that plug.

Thanks!

Tranny temps aren't an issue, and I think if I install an external cooler that it might have reverse effects during the wintertime. Just was looking into it.



Of course that depends on where you live Tim. In your case the tranny cooler may not be a good idea unless you tow stuff. I have the GM tranny cooler kit for my GTP. Just haven't decided whether to install it yet. I'll see how the summer temps are.

Would you use your external cooler in conjunction with your existing one? Or bypass the one in the radiator all together? (Just curious as to the benefits of each)

In conjunction per the install instructions. See link.

Click here (http://www.geocities.com/fastxtc/gp/auxcooler/)