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I recently got my transmission rebuilt and had a shift kit put into it. The problem is that now when i go WOT, the car will hit the rev limiter a couple times before it shifts. Obviously this is not good for the motor and I am not sure where to start. I also had the car tuned at a local shop here in dallas after all the work was done. Can someone give me some insight as to where to start to get this fixed before i blow the motor? Attached is the build sheet for the transmission with all the work done. Car has heads/cam/intake etc. A4 with a 2800 stall. It was a 2.73 car and i put a 3.15 gear in it as well. It also gets extremely got inside the cabin if I drive for more then 30 minutes.
Hot inside the cabin after 30 minutes in Dallas? Unless you're running A/C, TOTALLY normal C5 trait. The rev limiter is obviously NOT! This is probably 99.9% a tune issue. You say it was tuned. I'd be headed back to the tune shop today!! Best of luck to you......
Last edited by Vetteman Jack; 06-07-2022 at 12:07 PM.
Hot inside the cabin after 30 minutes in Dallas? Unless you're running A/C, TOTALLY normal C5 trait. The rev limiter is obviously NOT! This is probably 99.9% a tune issue. You say it was tuned. I'd be headed back to the tune shop today!! Best of luck to you......
lol ya the heat thing just made me hope I wasn’t burning the trans up so that’s good to know that it’s common in a warm climate!
and I appreciate knowing now to start with the tune. I’ll reach out to the shop and see if they can fix it for me! Thank you! Didn’t know if I needed to start with trans shop or tune shop. Lol!
I believe that the reason is the gear change most likely. The ECU shift points and gearing/speed are related. That needs to be adjusted. The 273s were taller and the 315s are shorter so the speed at RPM changed - something along those lines. The guys in the Scan and Tune section will know immediately. I am thinking that the at the WOT shift the 273s were at a higher speed and the ECU is still looking for that speed but it hits the engine rev limiter due to the shorter 315s.
Last edited by Ed Ramberger; 06-07-2022 at 09:53 PM.
When you go from 2.73 to 3.15 rear drive ratio, the power control module must be reprogrammed OR you will hit rev limiter at WOT, usually in 1st or 2nd. Since 3.15 is a factory available ratio for a C5 A4, a knowledgeable GM dealer can do the reprogram--- but the reprogram will be based upon stock engine and transmission performance.
A BIG additional but-- With the performance cam and non factory shift kit, my opinion is that you need someone who is very experienced in C5 A4 characteristics and the cam performance to do the reprogram.
When I went from 3.15 rear drive ratio to 3.73, my car would hit rev limiter in 2nd and not upshift at WOT. I had A&A Corvette in Oxnard, CA do the reprogram. All good seven years and 15 track days later.
With regard to hitting the rev limiter, the C5 rev limiter is a fuel cut off and not nearly as hazardous to the engine as an ignition cut off. I have managed to hit rev limiter at least once or maybe three times on every session for the last fifteen track days and 45 sessions-- and my 2001, 118,000 mile, 24 track day A4 C5 seems fine.
I do worry about the stock A4 sun shell though. On my list.
Grinder is right. It’s the tune. I’ve been here before. Go back to the tuner, hopefully they are open to listen to you, or find a new tuner!
It is your gear change from 2.73 to 3.15. Don’t do anymore WOT until this is fixed… On the A4s, it’s the Vehicle Speed Sensor (VSS). The VSS is located in the diff, and it needs to be adjusted in your tune. If your tuner can’t figure that out, get a new tuner.
If you ask me how I know, I went through 2 melted clutches torque converters, a transmission until I figured it out through my own knowledge. Incompetent tuners. That’s why I hate most tuners out there because they think they know everything, they ruin your car, then blame mechanical parts and continue ruining other cars such as yours.
I’d say they didn’t tune the trans.
If they did, they certainly didn’t drive it.
Come on u should know better than this. if shops would do this they will start getting a good reputation. They don't want the extra money. they make too much already for an hr of tuning wot, not driviablely. And that would eat into their profits that they don't want. They have to keep up buying GRINDER lll his beer. He his the final say before the car goes out the door. How's that going.
I believe that the reason is the gear change most likely. The ECU shift points and gearing/speed are related. That needs to be adjusted. The 273s were taller and the 315s are shorter so the speed at RPM changed - something along those lines. The guys in the Scan and Tune section will know immediately. I am thinking that the at the WOT shift the 273s were at a higher speed and the ECU is still looking for that speed but it hits the engine rev limiter due to the shorter 315s.
Totally agree! Trans program wants to hit that higher speed, and has engine trying its best to find it!!!
When you go from 2.73 to 3.15 rear drive ratio, the power control module must be reprogrammed OR you will hit rev limiter at WOT, usually in 1st or 2nd. Since 3.15 is a factory available ratio for a C5 A4, a knowledgeable GM dealer can do the reprogram--- but the reprogram will be based upon stock engine and transmission performance.
A BIG additional but-- With the performance cam and non factory shift kit, my opinion is that you need someone who is very experienced in C5 A4 characteristics and the cam performance to do the reprogram.
When I went from 3.15 rear drive ratio to 3.73, my car would hit rev limiter in 2nd and not upshift at WOT. I had A&A Corvette in Oxnard, CA do the reprogram. All good seven years and 15 track days later.
With regard to hitting the rev limiter, the C5 rev limiter is a fuel cut off and not nearly as hazardous to the engine as an ignition cut off. I have managed to hit rev limiter at least once or maybe three times on every session for the last fifteen track days and 45 sessions-- and my 2001, 118,000 mile, 24 track day A4 C5 seems fine.
I do worry about the stock A4 sun shell though. On my list.
As for less hazardous to the engine, in some ways, but not so much in others. If you miss a gear at 6,500rpm in an M6 car, the fuel cutoff happens later than an ignition cutoff, and you could seriously damage the engine, even with the fuel cutoff. Happened to my friend, who trashed a cam and lifter! Electronic cutoff is instant. There are advantages to both........
I love how everyone is giving their opinion without real experience on the exact issue lol that it’s the trans, ecu, pcm, etc it’s none of those.
@2002xlt - private message me and I can explain where your tuner needs to make adjustments for the VSS for the gear change. If you don’t make this change, you’ll burn through the clutch material in the torque converter and ruin your trans. You’ll thank me.
I love how everyone is giving their opinion without real experience on the exact issue lol that it’s the trans, ecu, pcm, etc it’s none of those.
@2002xlt - private message me and I can explain where your tuner needs to make adjustments for the VSS for the gear change. If you don’t make this change, you’ll burn through the clutch material in the torque converter and ruin your trans. You’ll thank me.
I dunno. I thought I said I believed it needed an adjustment to understand the different speed because of the gears (tune being in the computer) and advised that the guys in Scan and Tune would know immediately. I think that was more helpful than your sarcasm.
I dunno. I thought I said I believed it needed an adjustment to understand the different speed because of the gears (tune being in the computer) and advised that the guys in Scan and Tune would know immediately. I think that was more helpful than your sarcasm.
Well going through this exact issue costing me a lot of wasted time, money, converters, transmissions, and argument with tuners, I don’t want the OP or others to go on a goose chase like I did and narrow it down to what it is.
Yes, you are right in theory. On C5s, the speed adjustments are controlled in the diff by the VSS not the speedometer. Many other late model GMs are tuned off the speedometer but not the C5. The VSS counts the rotation in the gears and sends that information to the computer to shift. Standard 6 speeds don’t have this problem.
When you go from 2.73 to 3.15 rear drive ratio, the power control module must be reprogrammed OR you will hit rev limiter at WOT, usually in 1st or 2nd. Since 3.15 is a factory available ratio for a C5 A4, a knowledgeable GM dealer can do the reprogram--- but the reprogram will be based upon stock engine and transmission performance.
A BIG additional but-- With the performance cam and non factory shift kit, my opinion is that you need someone who is very experienced in C5 A4 characteristics and the cam performance to do the reprogram.
When I went from 3.15 rear drive ratio to 3.73, my car would hit rev limiter in 2nd and not upshift at WOT. I had A&A Corvette in Oxnard, CA do the reprogram. All good seven years and 15 track days later.
With regard to hitting the rev limiter, the C5 rev limiter is a fuel cut off and not nearly as hazardous to the engine as an ignition cut off. I have managed to hit rev limiter at least once or maybe three times on every session for the last fifteen track days and 45 sessions-- and my 2001, 118,000 mile, 24 track day A4 C5 seems fine.
I do worry about the stock A4 sun shell though. On my list.
Jim, I've got a totally stock 4L60E in my C5. For the last 65,000 miles, it's made at least 30 dragstrip runs with a built LS7 yanking on it. I have almost 130,000 miles on my car, never had an issue, although I think road racing would probably be harder on it than drag racing. I agree to a point that, maybe, I did get a "good one." But at some point, being lucky, or getting a good one cant be the whole story. My .02, FWIW.....
I dunno. I thought I said I believed it needed an adjustment to understand the different speed because of the gears (tune being in the computer) and advised that the guys in Scan and Tune would know immediately. I think that was more helpful than your sarcasm.
I'm with you, Ed. It is in the tune, which I also addressed. I dont see where we were off topic at all.....
I appreciate all the feedback from everyone on this topic. I will be taking the car into the tuner in the next week or so and let you all know how it goes. The shop has great reviews here in Dallas, which is why i took it there, so lets see how their customer service is!!
I'm with you, Ed. It is in the tune, which I also addressed. I dont see where we were off topic at all.....
FWIW I never said off topic, I said opinions… just saying “it’s the tune” doesn’t pinpoint what the issue is in the tune. If the OP goes back to the tuner and says, my tune is off and they don’t know where to make adjustments in HPtuners, it won’t be done right.The exact issue is the VSS. I hope they find and make the right adjustments before they ruin his transmission
Part throttle shifts are dictated by mph and throttle position.
When you change gears from say a 2.73 to a 3.42 it will shift by mph but the rpm will be higher than it was before. So the change for the lower gears will be to lower the mph in the tables. Part throttle is pretty much user preference. Easy to adjust.
Full throttle is a different set of tables. It shifts by mph and rpm. The system first sees the mph, then attempts to shift at the rpm in the table.
Mechanically, the trans takes time to shift, so if the mph happens too close to the rpm, it just doesn’t shift. Which it will do after a rear gear change.
The tuner can either drop the mph tables to hit the shift rpm. Or, if the owner wants higher shift rpm, the tuner will raise those numbers. Might have to raise the rev limiter as well.
Shift time can also be reduced. I think stock is something like .25 seconds.
Of course to test all this it’s a straight stretch of road, foot to the floor. 2-3 shift happens near 90 mph. Tuner may not wish to do that. Depends on if you have a safe place to do it.
Hence my comment that they didn’t drive it to test WOT shifts. The customer certainly did…..
06-07-2022, 12:41 AM
Car hits rev limiter after trans rebuild and tune
