Transmission Does Not Hold Gear and Spikes RPMS.

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I will make one calibration change for an additional $100 per change. For example, changing a shift point for a given gear is $100 vs changing a shift point and a pressure setting would be $200. That value can be used towards the full custom tuning price.

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Fri, 03/04/2022 - 11:16

#1

jrager

Transmission Does Not Hold Gear and Spikes RPMS.

Ok so here is the Vehicle info. I have Swapped a 2017+ L83 and 6L80 into a 2009 Jeep JKU and am using a Motech/Mocan Can bus translator for the Jeep and GM side to talk to each other. The GM side will run stand alone. I am using HP tuners to tune.

The Engine is running a Stock tune right now with only Start Diagnostics and DOD Disabled.

The trans I have tried stock tune to VSS manipulation vias gearing to now using the HPTuner calculator to calcualte the shift tables with 42 inch tires and 5.38 gearing.

There are a couple of folk I have found doing these swaps that are having same issue.

Problem:

When driving the tansmission will lose gear and spike RPMS and then catch gear.

Whan I look at the log and watch the Gear selector what is happening is a routine.

The VSS sends a Speed signal going from normal VSS speed to 158Mph then sends Park then Neutral ( RPMs Spike) then MPH drops back to normal then regains gear. You can see this parttern happen in the log files and watching the gear indicator.

I will say the athe closer the VSS is to actual the less frequent it occures but it still occurs consistantly.

I have replaced the TCM and Valve bodies and re flashed to GM stock

I have replaced the VSS

I have replaced the Gear switch

I have tried the Bluecat calcs.

I have tried several different tune strategies.

I am at a loss for how approach from here any help is greatly appreciated.

I attached a log that shows the spike.

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Transmission Does Not Hold Gear and Spikes RPMS.

Click on the "SUBSCRIBE" tab to sign up. I will not respond to technical questions unless you are a paid subscriber. Calibration and Config files will not open directly from the site, they must be downloaded to your computer in order to open.

NEW!!!

I will make one calibration change for an additional $100 per change. For example, changing a shift point for a given gear is $100 vs changing a shift point and a pressure setting would be $200. That value can be used towards the full custom tuning price.