ShowstoppaTransAm

I have a 2001 Trans Am automatic. I recently had the rear axles replaced and changed to a 373 gear. I also had new plugs and wires installed. Right after that I started noticing when i'm going 45-60 mph the RPM shoots up to 3,000-4,000. The car doesn't accelerate. I stay the same speed but the engine revs really high. I usually let off the gas and it stops. I have 170,000 miles so i thought it must be the tranny. Even though i never had any slipping. I took it to the guy that did the rear end. He has a GREAT REPUTATION by all the hot rodders in town. He had it for 3 days and could never get it to replicate the sympton for him. Well me being stupid when i got the car back and it did it i stomped the gas and let it rev for 1 minute. I toasted the tranny and the car wouldn't go over 20mph. Well now he rebuilt it and it's still doing the same thing. He suggested I buy a programmer because my speedo was off when he changed the rear gear to a 373. He said maybe the computer was confused because the speedo was off. I bought a Hypertech and corrected the speedo. It still dose it. The only code my car has is a lean code that it's had for 7 years when i put a ram air intake and a granitelli mass air flow sensor. the car has run GREAT with that lean code for 7 years and I don't have any other code. Every shop I've called seems to be LOST. I don't no where to take my car. I'm clueless. I thought the speedo was the problem but it wasn't. If anybody can HELP ME PLEASE DO. I'm totally lost as which direction to go.

AGAIN WHEN DRIVING 45-60 MPH RPM SHOOTS UP TO 4,000 PLUS UNLESS I LET OFF THE GAS. THIS HAPPENS WHEN I'M DRIVING DOWN THE HIGHWAY EITHER BY PRESSING THE GAS OR USING CRUISE CONTROL.
CAR RPM JUST STARTS REVING UP LIKE I STOMPED ON THE GAS BUT DIDN'T.
CAR NEVER SLIPS. IT FEELS LIKE IT'S NOT IN GEAR

WHAT I'VE DONE
REAR AXLES AND 373 GEARS
NEW PLUGS AND WIRES OEM GM PLUG / BOSCH WIRES
REBUILT TRANNY
HYPERTECH TUNING TO CORRECT SPEEDO

CAR 2001 TRANS AM AUTOMATIC 170,000 MILES


THANKS FOR ANY AND ALL HELP

I'm in Savannah GA if somebody knows of a shop close that can help please let me know

Paul Bell

iTrader: (9)

I believe the RPM's at like 60 MPH with a 3.73 rear should be around 2,200 RPM. Even if the torque converter lock-up was malfunctioning, the engine speed would only jump a bit but certainly not up to 3-4 grand.

It sounds like the transmission is downshifting to second gear.

Please elaborate on the conditions this was under. Highway? Have you scanned for any codes? Is the SES light on?

What transmission pan do you have? Here's a possibility (but if that guy has a GREAT reputation as you say, he woulda known about this):

There is a hole in the pan rail for the drain of the innermost chamber of the servo when 4th gear applies. There is at least one aftermarket pan that allows the pan gasket to partially or completely block the hole, and if it's blocked, the servo can't engage 4th gear

white99ta!!

thats rite around where your tc should go into lock up. Does it go into lock up or does it do that instead? when you said you toasted your trans did you check the tc? Someone could have a great rep with some cars and not others. If he has a great rep with carbed cars he might not no **** about the computer systems. you need to factor in your gears and tire size.

ShowstoppaTransAm

@Paul yes my service soon light is on. Its been on for 5-7 years. Every since I put a granitelli mass air flow sensor. It has a lean code. AutoZone says the code means i need a new mass air flow sensor or oxygen sensors. Pontiac did a recall on my cats and they put new oxygen sensors on but the code stayed on. Factory pan.
The condition: highway and back road. It never does it in town red light to red light. When I'm on straight shots. I can be cruising (with/without cruise) about 45-60 and wham RPM shoots up for no reason. It might be a down shift. If it is I never feel it. The car never jerks.
Then again it does feel like I'm not in the wrong gear.
Does this sound like a computer issue or a tranny?

ShowstoppaTransAm

@white he rebuilt the tranny and installed a new tc. You're right he's not really into the computers. He wasn't able to set my Speedo when he changed my gears. With that being said he does quite a few f body's and gto's. I've seen some bad cars in his shop. He seems to think it's a computer problem. Even though it has no other code than running lean.

white99ta!!

You could have air coming in after the maf. Check for leaks, you can spray carb cleaner and if it hesitates theirs a leak. You can try cleaning the maf with maf cleaner and you can also check the ffuel pressure. All of that is cheap. My car was running to lean for a little cause I had air coming in before the 02s so I replaced the header gaskets and collector gaskets and it's fine now. Hopefully it's a simple fix for you. If he didn't calibrate the speedo you should def get that done. Mine wasn't rite after 373s and when launching from stall it would launch in 2 and my shift points were messed up. Hope this helps

Paul Bell

iTrader: (9)

Yes, false air (air not measured by the MAF) could screw up the PCM. That in combination with the incorrect speedo may be causing the PCM to do weird things.

I'd get the PCM fixed for the new ratio and hunt down and fix the cause of the codes before proceeding.

Hows your transmission cooler and lines? Running the correct filter for the pan? You should drop the transmission pan and inspect the servo dump port in the pan rail to make sure it's OK and the gasket isn't blocking it. What pan are your running? How are all your ground points? Any strange electrical issues or erratic voltage jumps? Battery connections clean and solid?

Worst case scenario, transmissions today have aluminum valve bodies and can wear to the point of mysterious malfunctions like yours.

ShowstoppaTransAm

My Speedo is CORRECT. I bought a hypertrech handheld like the transmission guy told me to and calibrated it. No air leaks. I'm not worried about the lean code. Car has ran great 5-7 years with it. I should state my car doesn't do this all the time. It randomly happens.
transmission cooler and lines. Physically looking their great. My car looks almost new when you look under it. Garage kept and never in the snow.

ShowstoppaTransAm

Okay i took my Mass Air Flow sensor off and a rubber seal was not all the way seated on the back off the air lid. I put everything back together and now the SERVICE ENGINE SOON code has been off for 3 days now. I have NO CODES showing up.

I've figured out when the car goes over a hill this is when it does it. If i'm holding the same speed (60mph) when i go over a hill the car eases off the gas coming down hill. When the car gets gas after this to maintain the same speed this is when it does it. Instead of keeping the same speed the RPM shoots up to 4,000 plus unless i let off the the gas. The car want go any faster just the RPM goes up. The car will run bad until i bring it to a stop. Then it'll run fine until i hit a hill again. It doesn't do it all the time just most of the time.

ShowstoppaTransAm

I had the 2 shift solenoids installed but it didn't help.

Somebody please help

white99ta!!

Could be the iac ( idle air control) or the tps ( throttle position sensor) or both. If your tps isn't working properly it could tell the computer the throttle isn't open enough to idle and cause the iac to try and fix it. Replace them and if it's not the problem take them back just keep the receipt and the old iac and tps.

ShowstoppaTransAm

@white99 do you know if either one will throw a code if there bad? I guess I'll try it I'm at a stand still. I hope this works.

94fyechkn

Did you ever figure it out? Currently same situation with mine