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Thread: 2008 Charger Drivetrain Swap Transmission Code P0733 - Gear 3 Incorrect Ratio

  1. #1
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    2008 Charger Drivetrain Swap Transmission Code P0733 - Gear 3 Incorrect Ratio

    Hey everyone, I am new to Dodge Tuning and I am currently having a problem with a car I am tuning. A 2008 Charger drivetrain has been swapped into another vehicle and it is creating all sorts of headaches for me. The factory dash and most components are in the new vehicle. The engine is built and is supercharged. The transmission is also built. I have been able to get the vehicle to start up and idle well. I have also rough tuned part throttle. Beyond that the car will rev in neutral, but will not rev when moving. I am getting code P0733 which is "Gear 3 Incorrect Ratio", which I feel is throwing it into limp mode. Any thoughts on what might be causing this? Could it be a transmission issue? And how would I diagnose it? I don't feel any noticeable slip when driving it. At first I thought it was a traction control issue, since I initially had the car on the dyno. I pulled the car off the dyno, and the same thing occurs going down the road. 3000 RPM seems to be the max and the pedal feels dead. I found out the vehicle has had the ABS removed and that has given me some concern since the traction control would be effected by this. The traction control lights are lit on the dash. I believe I have turned off the traction control in the tune. Any insight would be appreciated.

    Thanks.

  2. #2
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    I found this generic answer by googling.

    Code P0733:

    When the code P0733 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is seeing a greater than a specified RPM difference between the rotational speed of the Input RPM Sensor and the Transmission Output RPM Sensor when the vehicle is in 3rd gear. This can occur during shifting or when driving at steady speeds. It often implies that the transmission is slipping.

    So basically, engine speed x gear selection = X. If the computer doesn't see "x" while it's doing it's calculation, it throws the code. I would start with the easy things like checking to make sure your final drive ratio is the same as what the computer is expecting. If it is, then I'd talk to whomever did the transmission and make sure that they didn't change any of the ratios for each gear. If those check out, it possibly could be slipping since the trans isn't fully broken in and you're at a much higher power level now with the supercharger.

    I don't know enough about Chrysler products to help you much further than this but just remember, the computers in these cars don't really "think". If 1 + 1 doesn't equal 2, they get fussy.

    Since you said that you can't even get past 30 mph, I'd almost bet it has something to do with your final gear ratio.

    As a last ditch effort, I'd try changing the "specified" difference that the computer allows. There's probably a table or option hidden somewhere in your tuning software. If you could max that value out, it should let you drive the car without it going into the limp mode you mentioned. Just remember, once maxed out, there would be no safety barrier preventing you from doing damage to the trans and/or rear end. If you're worried about either of those 2 not being strong enough for the power level that you're at now, I'd make small adjustments slowly until you can drive it normally or the value gets maxed out.

  3. #3
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    Thanks for your response, I really appreciate it. I am starting to believe that since the vehicle no longer has the ABS or wheel speed sensors, it is causing the problem. Since the computer is not getting the expected output speed it expects for a given input speed, it thinks the transmission is slipping and throws the vehicle into limp mode. I spoke with a gentleman last night that was more familiar with Dodges and he was thinking the output speed is referenced from the ABS system. I plan to investigate more today. Thanks again and I will look through the tune for limits I can adjust as you suggested.

  4. #4
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    If there's no sensor on the output shaft of the trans, I would bet it is referenced from the wheel sensors.

  5. #5
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    That is what I am hearing . The output shaft rpm is staying at a high value and not changing with speed. I am sure that is why it is kicking the code. After further review, the car has rear wheel sensors, but not front wheel. The ABS and TM module is still in the car, but no brake lines are connected. I need to get a scanner on it to see if I am getting any pulses from the rear wheel sensors. I also want to check to see what it would take to put the front wheel sensor back in place, and finally what effect there is by not having the brake lines routed through the ABS pump.

  6. #6
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    On the brake line routing, it "should" just throw an ABS/TC INOP light and turn those functions off until it's "fixed". In order to determine if the car is sliding, the computer definitely would be comparing all 4 values. Once it computes which wheel is different, it would normally release the brake at that wheel allowing more traction for steering instead of stopping until it figures out it can start braking again. Of course, that would all be happening 100's/sec but you get the idea.

    If you're able to get the front speed sensors installed into the new vechile and wired back into the harness, that should improve driveability. I don't think your P0733 has anything to do with the front wheel sensors though.

    Either, the rear sensors aren't sending the *right* signal (18x, 24x, ect.) that the computer is programmed to. Or the tire size is different from programmed. Or the final drive ratio is different from programmed. Or the gears in the trans are different from programmed. See where I'm going with this? Your problem is definitely because the computer is programmed for X setup and your setup is different from what it thinks is there.

    In order to figure this out, just go back to the basics as you go over the car. Write down the tire size. Count the rotations of the drive axles compared to trans shaft and calculate your final gear ratio. Get the part # off the wheel sensors themselves.

    After you've gathered all the data that you can, go back to the tune and check each parameter. Make sure that every parameter matches what you actually have. Chances are, you'll find that 1 little thing that's off between the car/tune and fixing that will solve it.

  7. #7
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    Thanks for the response. I am still in the process of getting the front wheel sensors installed and finding a scanner that can read the pulses. I have already set tire size and gear ratio, but it is probably a good idea to recheck. I will update with the results.

  8. #8
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    can you post your tune?