Hi Guys,
I have a jeep wrangler outfitted with the GM L86 6.2L Gen 5 Engine and 8L90e transmission out of a 2015 Cadillac escalade. The Jeep runs and drive but I believe that there is a lot of room for improvement when it comes to the transmission tune that the installer is using. Therefore, I am spending some time looking at the current tune and trying to understand why the transmission shifts so poorly.
First and foremost, here are a few things worth noting:
+The modified Jeep and the escalade weight nearly the same (5,000 ~ 6,000 Lbs range).
+The jeep is geared at 4.10 and runs 35" (true to size) tires and the escalade usually comes with 3.23 gears and 32" tires.
+The escalade has a top speed of 130 MPH (not sure if it is governed or not, but the car is made to handle that speed) whereas the Jeep should be limited to 100 MPH.
The issues I am facing with the current transmission tune are listed below:
+The transmission is very quick to upshift and stays most of the time in 8th gear. It feels like it's lugging the engine.
+When you depress the pedal hard enough for the transmission to downshift, it drops too many gear and ends up going back to the 8th gear shortly after.
I have a few general questions when it comes to the VCM editor software:
1-Windows software usually come with a help menu that is indexed and that explains the software's operation and parameters. It seems that it isn't the case with the VCM editor. Is there a manual that can be downloaded? If so, can you please share the link.
Update on question 1: found the link. Here it is: https://www.hptuners.com/help/
However, this help guide applies to version 2. We are at version 4... Is this going to get updated soon?
2-Is there a parameter hierarchy guide that shows which parameter supersedes the other? Let me explain. Looking at the WOT shift RPM vs Shift - Normal table, I noticed that shifting from 1>2, 2>3, 3>4, 4>5 and 5>6 is set to 5,600 RPM. However shifting from 6>7 and 7>8 is set to 8,192 RPM! My engine simply cannot rev at 8,192 RPM. Therefore there must be a parameter set in another table that supersedes this table values and limits the engine to the max governed 6,400 RPM limit. Moreover, according to this table, the transmission will never upshift to 7th and 8th gear, because the engine will never rev that high.
3-Is there a table hierarchy guide? If so where can we find it?
I also have a question regarding the WOT Shift Speed vs Shift ? Normal Table. Here are the parameters:
2>1 | 19
3>2 | 36
4>3 | 59
5>4 | 76
6>5 | 107
7>6 | 313
8>7 | 313
1>2 | 23
2>3 | 42
3>4 | 63
4>5 | 81
5>6 | 94
6>7 | 313
7>8 | 313
How is the transmission supposed to upshift 5>6 @94 MPH and downshift 6>5 @ 107 MPH ?
It doesn't make any sense.
Also why is the 313 MPH value even used in this table?
update: It turns out that by using the 313 MPH value which isn't attainable, the transmission will never upshift to 7th or 8th gear at Wide Open Throttle (WOT).
Thank you!