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tranny problem (typical) trannyman?

GTX

GTX

New member
well yesterday im driving with my friend in his 98 gtp with 130,000 and all of the sudden the rpms started bumpin up and down rapidly while cruising at highway speeds with light load under heavy load it would be fine. then at stop lights it would whine really bad and shudder the car and move slowly but if you punched it it would be fine, we got it back to the house doing 100+ keeping the foot on the pedal the whole way the tranny seemed good when driving like this, but get it back to a stop it would act up. we did for $h!t$ and giggles a flush and service to see if it would clear it up, it did but now it just bumps really hard and feels like it slips and catches. is the tranny gone? or TC? valve body? whats the best fix? he just bought the car like 3 weeks ago. can we get around doing the tranny? im not a tranny expert by any means so opinions/ideas would be great
 
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Re: tranny problem (typical)

I had something simmilair but not as bad as your describing. It turned out to be the maf acting up and causing the engine to do these weird surges that felt like the trans bumping. I had no lights or codes from it either. Might try swapping it out and seeing it it fixes it.
 
Re: tranny problem (typical)

were you RPM's moving up and down at about 1500-2000 rpm or 65-70 MPH?
 
Re: tranny problem (typical)

did you guys get any check engine lights or codes for the MAF? how did you determine that to be the problem?
 


Re: tranny problem (typical)

were you guys running oiled/over oiled air filters when you had the MAF problem? he has the stock air filter on his car so no oil to contaminate the MAF
 
No I had no lights or codes at all and I was running a stock air filter. I found if I touched the maf when the car was running it would surge sometimes. That was the only indication it might have been a problem. I have since replaced it and have not had the problem again.
 
There is a lot of info about your problems on my website if you click the info link in my sig below. The maf sensors have been known to cause problems as well and if excessively dirty can cause low line pressure, but also if the maf signal is low it directly effects fuel trims and the pcm will be adding fuel to compensate for this and this is something that can be seen on a scan tool.
 
sounds like he has bad valve body. i cleaned his MAF today, and the problem persisted on and actually the car slips and hits a hard 3 rd gear , but also the shifts ( with performance shift on ) are weak and almost feel slipping. im thinking pressure solenoid and valve body. ive also read that a bad temp sensor can cause poor shifting is this true? its strange because it does shift through every gear and now the RPM bumps arent happening on the freeway. it doesnt seem like a bad transmission to me, but something is going on with it
 
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today i added some sea foam to it, and drove it around it seems so far to be doing good, however the shift points are a little off and dont seem as firm with the performance shift engaged, kinda nervous to drive around more than 20 miles though
 


It sounds like overall you have low pressure. This can only be verified with a pressure gauge and all other operations of the trans can only be checked with a scan tool to see what is exactly going on and also with the scan tool hooked up you would be able to check over all of the engine sensors to verifiy they are working properly.
 
There is no positive answer without properly testing the car. The pressure control solenoid may be fine but the trans has enough wear and internal leaks to cause the low pressure, but again without a pressure gauge and scan tool all you can do is guess
 
i have a snap on mt2500 scanner, i dont have a transmission pressure gauge, i do have an oil pressure gauge are they one of the same? when i go to the scanner under transmission what are readings i should be looking for?
 
A transmission pressure gauge reads up to 300+ PSI which is mandatory to have when testing transmission line pressure. Watch your shift times. If you see the PCS amps go to 0.00 then the pcm but it in a max line pressure state to prevent it from burning up. I have a chart that you can use to test line pressure in all of the ranges while having a scan tool hooked up to command different pressure. You should be able to go under Functional Tests on the scan tool and command PCS amperate from 1.0 amp down to 0.0 amp, the lower the amperage the higher the psi will be. Often the solenoid acts up only when warmed up so you can check this out cold and then when the car starts acting up you can check it again to compare numbers, but you will need a proper pressure gauge to do this as the engine oil psi gauge is not going to work.
 


i just drove it around city and freeway, and its almost non existent now, a few times under load up a hill it would bump the rpms up and down but only like a 100 or so
 
GTX said:
well yesterday im driving with my friend in his 98 gtp with 130,000 and all of the sudden the rpms started bumpin up and down rapidly while cruising at highway speeds with light load under heavy load it would be fine. then at stop lights it would whine really bad and shudder the car and move slowly but if you punched it it would be fine, we got it back to the house doing 100+ keeping the foot on the pedal the whole way the tranny seemed good when driving like this, but get it back to a stop it would act up. we did for $h!t$ and giggles a flush and service to see if it would clear it up, it did but now it just bumps really hard and feels like it slips and catches. is the tranny gone? or TC? valve body? whats the best fix? he just bought the car like 3 weeks ago. can we get around doing the tranny? im not a tranny expert by any means so opinions/ideas would be great
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Maf...what was your MPG? fuel consumption? all that stuff, give us more info?
 
get to 40ish, wait for the torgue converter to lock up and hit the gas to raise the boost but not downshift and feel if it is slipping or missing in the cylinders....and what tranny are you running? 4t65e or hd?
 
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