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Thread: 4T80e swap

  1. #1
    Tuner in Training skalor's Avatar
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    Nov 2002
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    4T80e swap

    I'm having trouble getting the proper calculated gear ratios correct with the 4T80 swap. I changed the individual gear ratios in Tiny Tuner because they aren't accessible in HP Tuners. I think my main problem is the ISS and VSS difference between the 4T65 and 4T80. The 4T65 has a 25 tooth ISS and a 30 tooth VSS. The 4T80 has a 39 tooth ISS and a 31 tooth VSS. The stock 4T65 was a 2.93 FDR so the differential was a 3.29 with 1.121 sprocket ratio. The new 4T80 has a 3.11 differential with a 1:1 sprocket ratio. I'm sure I'm going to be running some messed up numbers because I cannot changed the ISS and VSS numbers in the PCM. Any help would be greatly appreciated.
    '89 Olds Cutlass Ciera International Coupe - '99 L67 minus the M90 plus a 60-1

  2. #2
    Tuner in Training HOYS's Avatar
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    I've been doing some messing around with Tiny Tuners myself. Do you have a .bin file for a vehicle stock with a 4T80E?

  3. #3
    Tuner in Training skalor's Avatar
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    I was out logging today after I made some changes to the individual gear ratios in the bin. I set 1st to 3.984, 2nd to 2.750, 3rd to 1.688, and 4th to 1.141. After getting on it a little bit, it set a P0730(incorrect gear ratio) in 3rd while it was in decel. After looking at the logs, it looks like while in decel it dropped to the 4th ratio(1.141) and that's when the code set. This happened around frame 1650 in the log. In the log below you can see the ISS to VSS ratio, which is labeled sprocket ratio. The actual sprocket ratio is 1:1 in the 4T80 so that's what it's set to in the tune. Also, keep in mind that it will not shift 3rd or 4th on it own. I can manually set 3rd or 4th via the scanner so if you have any ideas why it won't shift past 2nd on it's own I'm open to them. I'm just about ready to give up on the stock PCM controlling a 4T80. lol
    '89 Olds Cutlass Ciera International Coupe - '99 L67 minus the M90 plus a 60-1