What needs changing in tune, t56 to th400 '03 Cobra?

[badcobra]

I am dropping in my newly built th400 any day here. What all do I need to change in the tune? I have the reluctor wheel with 5 evenly spaced teeth and the GM sensor for the speedo. I know I need to tweak those parameters, but what else? It's an amz1 processor and using PRP.

We'll be going to the dyno for WOT, but I want to have all the other changes in the car before I go so I'm not wasting time/money. Thanks!

 

[03Steve]

Give me a buzz tomorrow. I've done this on a few cars locally now.

 

[badcobra]

Awesome, thanks Steve. I'll give you a buzz.

 

[badcobra]

Thanks for the help Steve! :beer:

 

[vip3r1850]

Thanks for the help Steve! :beer:

Hi, new 400 on the way as well.

Quick question. Did you have the stock 40 tooth reluctor ring ? Can you post a link to the GM sensor ?

Can you post the parameters that need to be changed in PRP ?

All help greatly appreciated ! Been searching for hours for a solution.

 

[badcobra]

So I can help with the part numbers and info that 03Steve gave me on the tune. The part numbers you need are:

8655315 Reluctor
8655291 VSS
12085498 VSS connector (they call it fog lamp connector, but its correct)

I bought the bottom two off Rock Auto. The reluctor wheel is not easy to find as its discontinued. I finally got it from GMPartsgiant.com. My tranny guy ground the 40 teeth down to 5 evenly spaced teeth. Make sure you keep the t56 harness as you will need that for the speed sensor and backup lights. You will just basically chop off the speed sensor plug on the harness and wire in the GM sensor. It's just two wires so it's easy peasy.

Next, in your tune go to System Switches and changes the OSS number of teeth or holes from 12 to 5. Steve suggested setting the rear end gear ratio to 5.00. You can adjust the tune to get the speed correct using just a simple GPS app on your phone. I just got my th400 in so I haven't fine tuned yet, but I can verify from just running it on the hoist that my speedo does work. It will just need a little tweaking to get it accurate. This should be enough to get you going with confidence that it will work and hopefully help anyone else searching in the future.

 

[03Steve]

For an ABS sensor - number of holes is 10, rear gear ratio is 5.00.

 

[vip3r1850]

So I can help with the part numbers and info that 03Steve gave me on the tune. The part numbers you need are:

8655315 Reluctor
8655291 VSS
12085498 VSS connector (they call it fog lamp connector, but its correct)

I bought the bottom two off Rock Auto. The reluctor wheel is not easy to find as its discontinued. I finally got it from GMPartsgiant.com. My tranny guy ground the 40 teeth down to 5 evenly spaced teeth. Make sure you keep the t56 harness as you will need that for the speed sensor and backup lights. You will just basically chop off the speed sensor plug on the harness and wire in the GM sensor. It's just two wires so it's easy peasy.

Next, in your tune go to System Switches and changes the OSS number of teeth or holes from 12 to 5. Steve suggested setting the rear end gear ratio to 5.00. You can adjust the tune to get the speed correct using just a simple GPS app on your phone. I just got my th400 in so I haven't fine tuned yet, but I can verify from just running it on the hoist that my speedo does work. It will just need a little tweaking to get it accurate. This should be enough to get you going with confidence that it will work and hopefully help anyone else searching in the future.

For an ABS sensor - number of holes is 10, rear gear ratio is 5.00.

Thank you both ! Just what I was looking for.

Quick question:

Let's say in theory if I were working with a performance transmission builder (will remain nameless for now) who has the ability to machine custom reluctor wheels and he machined me a 12 tooth wheel and I used that with the GM VSS, would I need to make any adjustments in the software ?

I am assuming everyone is cutting down to 5 teeth because that is the only way to get evenly spaced teeth if you start with 40 (keep halving them ie. 40 down to 20 down to 10 down to 5)

Thanks

 

[badcobra]

No way to know for sure on the tune until you try out the new parts. If you have pro racer, you can make the adjustment yourself, it's very simple...or have your tuner send you adjustments.