Tranny problems due to aftermarket TB?
11-12-2003, 07:59 AM
#1
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Tranny problems due to aftermarket TB?
I have heard people say this before. Is it really true? I know I needed tuning to really take advantage of a larger TB, but will it eventually cause damage to a tranny if the car isn't ever tuned for it? The reason I ask is because yesterday I floored it at around 20 mph in my A4, and it felt as if the tranny slipped or something. I am hoping it is a mount or something and not the tranny itself. BTW, I have a BBK/Edlebrock 52mm TB. I've been having a lot of small problems add up lately(o2 sensors, stretched throttle cable, etc.) and I don't want a big problem like my tranny now...especially when I am trying to save up for a 3.73 install.
11-12-2003, 08:36 AM
#2
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The stock TB is good for quite a bit... I have a 52mm TB on my car and it is adequate for the stroker...
No relation between TB and tranny. Different ends of the dog. If your tranny is slipping it will not get better on its own. Make certain the fluid level is full befre you worry. If the fluid level is full, and it is slipping, drive it real easy. Whomping on it will make it worse.
No relation between TB and tranny. Different ends of the dog. If your tranny is slipping it will not get better on its own. Make certain the fluid level is full befre you worry. If the fluid level is full, and it is slipping, drive it real easy. Whomping on it will make it worse.
11-12-2003, 09:06 AM
#3
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It's been posted on the LT1 Edit list for some time now that there is indeed a correlation between the different MAP pressures provided by a larger TB and early transmission failures. There are several Tranny shop guys on the LT1 edit list. The PCM commands the 4L60E based on feed back from the MAP(Manifold Air Pressure), TPS (Throttle Position Sensor), RPM and MPH. A larger throttle body provides a lower MAP reading for the exact same TPS as a stocker. MAP is utilized as a "load" parameter on the Engine and the skewed (In the PCM's determination) reading can cause the transmissions clutch bands to wear out/fail prematurely. This of course is related only to daily driven cars, not full time racers that spend most of their time at WOT.
Last edited by DirtyDaveW; 11-12-2003 at 09:10 AM.
11-12-2003, 09:19 AM
#4
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It is possible for A4 tranny problems with a larger throttle body but unlikely with a 52mm. I have yet to hear of people having actual tranny issues in an F-Body and being able to relate them to an aftermarket throttlebody. However, I have heard from the Impala guys that they do believe a 58mm throttlebody without the reprogramming HAS caused premature tranny failure... most likely because their cars are so much heavier than a Camaro or Firebird.
When adding an aftermarket throttlebody you don't need to change the tuning to get more hp... a larger throttlebody is accounted for "automatically" so to speak. The tuning "needed" for the A4 guys but not because of a hp issue. This is because Throttle Position Percent inputs into the tranny tables and is used to help determine how the A4 tranny shifts. Assume for a minute you just added a 58mm throttlebody. You are now headed to the store. Under these normal conditions, you are going to make your car perform exactly as it did before... this will require you to use less throttle to make the car go from, for example, 0 to 45 in 20 seconds. When you would take off from a light previously and drive normally, you would say have to make the throttlebody blades open 25% to do this 0 to 45mph in 20 second takeoff. Now, to do the same 0 to 45mph in 20 seconds with a 58mm throttlebody requires the blades to be open only 18% (for example). What the PCM thinks in this example is you are attempting to take off slower (even though you aren't) and uses this info in the tranny shifting scheme. Because it thinks you don't want to take off fast at all, it weakens the shift... makes it less firm. This MAY cause problems because you really are going along pretty good and the car is under decent acceleration yet the tranny is shifting like you aren't.
Having said all that, I ran a 58mm throttlebody on my Vortech supercharged 94Z for several years before reprogramming the PCM to account for the larger throttlebody and had no tranny failure. I did a rebuild and the clutches had seen better days but that may or may not have been caused by the 58mm throttlebody. With a 52mm throttlebody, I would not worry at all about it being the cause of tranny problems. You MIGHT notice weaker part throttle shifts but most likely you won't be able to tell the difference between a stocker and 52. However, there is a noticeable difference between the stocker and a 58mm throttlebody for part throttle shifting because of what I described above.
Bottomline, M6 guys have no worries when upgrading the throttlebody. A4 guys, IMO, have no worries with a 52mm throttlebody and stock programming but if they can easily change the programming, go for it. A4 guys with a 58mm throttlebody should have the programming "fixed" for the tranny concerns but, again, I don't believe there is any hard core proof that if you don't, tranny failure is right around the corner
When adding an aftermarket throttlebody you don't need to change the tuning to get more hp... a larger throttlebody is accounted for "automatically" so to speak. The tuning "needed" for the A4 guys but not because of a hp issue. This is because Throttle Position Percent inputs into the tranny tables and is used to help determine how the A4 tranny shifts. Assume for a minute you just added a 58mm throttlebody. You are now headed to the store. Under these normal conditions, you are going to make your car perform exactly as it did before... this will require you to use less throttle to make the car go from, for example, 0 to 45 in 20 seconds. When you would take off from a light previously and drive normally, you would say have to make the throttlebody blades open 25% to do this 0 to 45mph in 20 second takeoff. Now, to do the same 0 to 45mph in 20 seconds with a 58mm throttlebody requires the blades to be open only 18% (for example). What the PCM thinks in this example is you are attempting to take off slower (even though you aren't) and uses this info in the tranny shifting scheme. Because it thinks you don't want to take off fast at all, it weakens the shift... makes it less firm. This MAY cause problems because you really are going along pretty good and the car is under decent acceleration yet the tranny is shifting like you aren't.
Having said all that, I ran a 58mm throttlebody on my Vortech supercharged 94Z for several years before reprogramming the PCM to account for the larger throttlebody and had no tranny failure. I did a rebuild and the clutches had seen better days but that may or may not have been caused by the 58mm throttlebody. With a 52mm throttlebody, I would not worry at all about it being the cause of tranny problems. You MIGHT notice weaker part throttle shifts but most likely you won't be able to tell the difference between a stocker and 52. However, there is a noticeable difference between the stocker and a 58mm throttlebody for part throttle shifting because of what I described above.
Bottomline, M6 guys have no worries when upgrading the throttlebody. A4 guys, IMO, have no worries with a 52mm throttlebody and stock programming but if they can easily change the programming, go for it. A4 guys with a 58mm throttlebody should have the programming "fixed" for the tranny concerns but, again, I don't believe there is any hard core proof that if you don't, tranny failure is right around the corner
11-12-2003, 11:44 AM
#6
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I dunnon how much miles you got on your 97 AXE, but I had 78k on my car before I spun my bearings and 75k on the tranny when it started to go. All I had on my car at the time was a CAI, MAF, pullies, cat-backs and some bolt ons. I've heard that a lot of the 96's and 7's for some odd reason been having tranny issues. think I'll make a post.
11-12-2003, 11:36 PM
#8
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Transmission shift points for the 4L60E are controlled by the TPS, which bolts to the throttle body. If it's not adjusted correctly after you put the new throttle body on, you're transmission will get the wrong reading, and YES, it can damage the transmission if your TPS voltage is too low!
Frank
All-Trans Transmissions
Frank
All-Trans Transmissions
11-13-2003, 10:41 AM
#11
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Originally posted by 12SCNDZ
Transmission shift points for the 4L60E are controlled by the TPS, which bolts to the throttle body. If it's not adjusted correctly after you put the new throttle body on, you're transmission will get the wrong reading, and YES, it can damage the transmission if your TPS voltage is too low!
Frank
All-Trans Transmissions
Transmission shift points for the 4L60E are controlled by the TPS, which bolts to the throttle body. If it's not adjusted correctly after you put the new throttle body on, you're transmission will get the wrong reading, and YES, it can damage the transmission if your TPS voltage is too low!
Frank
All-Trans Transmissions
The adjustments needed for an aftermarket throttlebody would be changing of the tranny tables in the PCM, not the adjustment of the sensor itself. Are you sure you aren't thinking of the 3rd gen cars?
11-15-2003, 01:37 PM
#12
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Originally posted by Brent94Z
The throttle position sensor is auto adjusting on the 4th Gens... that's why it isn't slotted. At each ignition startup the PCM rezeros itself so to speak for current idle tps voltage. What's used in the tables is throttle position percent and not the voltage. So long as idle (closed blades) voltage is between around .25 volts and almost 1 volt the PCM will autoadjust to account and give 0 to 100% for a throttle position. So long as you get 0 to 100% throttle position percent and don't throw any codes, it doesn't really matter what the TPS voltage is. A voltage range of ~.23 to slightly over .9 volts for blades closed works in almost all cases with no codes and a tpp readout of 0 to 100%
The adjustments needed for an aftermarket throttlebody would be changing of the tranny tables in the PCM, not the adjustment of the sensor itself. Are you sure you aren't thinking of the 3rd gen cars?
The throttle position sensor is auto adjusting on the 4th Gens... that's why it isn't slotted. At each ignition startup the PCM rezeros itself so to speak for current idle tps voltage. What's used in the tables is throttle position percent and not the voltage. So long as idle (closed blades) voltage is between around .25 volts and almost 1 volt the PCM will autoadjust to account and give 0 to 100% for a throttle position. So long as you get 0 to 100% throttle position percent and don't throw any codes, it doesn't really matter what the TPS voltage is. A voltage range of ~.23 to slightly over .9 volts for blades closed works in almost all cases with no codes and a tpp readout of 0 to 100%
The adjustments needed for an aftermarket throttlebody would be changing of the tranny tables in the PCM, not the adjustment of the sensor itself. Are you sure you aren't thinking of the 3rd gen cars?
I had to slot the holes on my new TPS to get the right voltage.
But...Then again...Mine is a '93. TPS voltage doesn't have anything to do with my transmission, because I still have a 700. However, TPS voltage will cause problems in an electronically shifted (4L60E) transmission.
Frank
Last edited by 12SCNDZ; 11-15-2003 at 01:41 PM.
11-15-2003, 11:14 PM
#13
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Originally posted by 12SCNDZ
I was under that misconception also, until I put my new throttle body, and TPS on, and only had .3 V at idle, and 3.25 at WOT. Mine was throwing a "TPS VOLTAGE LOW" code.
I had to slot the holes on my new TPS to get the right voltage.
But...Then again...Mine is a '93. TPS voltage doesn't have anything to do with my transmission, because I still have a 700. However, TPS voltage will cause problems in an electronically shifted (4L60E) transmission.
Frank
I was under that misconception also, until I put my new throttle body, and TPS on, and only had .3 V at idle, and 3.25 at WOT. Mine was throwing a "TPS VOLTAGE LOW" code.
I had to slot the holes on my new TPS to get the right voltage.
But...Then again...Mine is a '93. TPS voltage doesn't have anything to do with my transmission, because I still have a 700. However, TPS voltage will cause problems in an electronically shifted (4L60E) transmission.
Frank
On my car I ran at .26v for probably about a year with no problems and no codes. I have run at .9 volts as well just to see what would happen and no problems there either (still had 0 to 100% TPP). I have heard of others running even a little higher than .9 with no codes.
The factory service manual goes into a little detail about what I've talked about above... but I haven't seen a factory manual for the 93? hmm?
11-16-2003, 12:47 AM
#14
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Didn't the 93's also still have the cable for the kick down? I know in the newer electronic transmissions pretty much all shifting is down by the PCM. I know with my 87 GTA, if the tranny kick down cable isn't adjusted right you run the risk of burning up the over drive in the transmission.
11-16-2003, 01:43 AM
#15
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LMFAO!
Just so you guys can figure it out some day....THE ONLY engine senser used to control the transmission is the TPS senor.
The TPS and VSS are used for ALL transmission functions..including pressure control. The Program knows at xx% TPS the engine should be making xxxhp and needs 'yy amount of pressure rise to control a shift at 'zz'MPH to obtain a shift in "m" amount of miliseconds.
Do a search this has been beat to death.
Then again what do I know?
Ellis
Lead Trans Tech
Kirkland Transmission
Just so you guys can figure it out some day....THE ONLY engine senser used to control the transmission is the TPS senor.
The TPS and VSS are used for ALL transmission functions..including pressure control. The Program knows at xx% TPS the engine should be making xxxhp and needs 'yy amount of pressure rise to control a shift at 'zz'MPH to obtain a shift in "m" amount of miliseconds.
Do a search this has been beat to death.
Then again what do I know?
Ellis
Lead Trans Tech
Kirkland Transmission