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View Full Version : Downshift flare 4-2/3-2 on lq4 swapped jeep



Dannn
August 29th, 2015, 05:32 AM
I've had an odd downshift flare ever since I swapped my jeep about 25,000 miles ago.

Specs:
98 Wrangler
03 LQ4
05 4L65E
3.73 Gears
33" tires
Wiring harness/0411 computer is out of a 2001 Yukon Denali XL that came with a 60e
Tune is based off a 156 2002 lq9 escalade if i recall.
Custom OS5 - issue was still present before the COS.

4th-2nd WOT downshifts are causing a flare. It seems like the trans engages 2nd, then slips a little bit, then re-engages 2nd. The flare gets worse the higher the speed. I'm attaching 2 pictures of log files with 60mph downshifts showing a slight 100-150rpm flare at 3k. I haven't had a chance to log a WOT downshift from a higher speed to see if the rpm flare is any higher.

Its been doing this for as long as I can remember. This is the 2nd trans i've put in the Jeep, and is strong everywhere else. The 1st one went out shortly after I built the Jeep due to the terrible mail order flash I had done before I got efilive. I've put probably 20,000 miles on this trans without issue, or the problem getting any worse. But both transmissions did the same thing.

Is it a tuning issue, or a mechanical issue? I've raised the shift pressures, bumped shift points, etc. Not sure if I should be looking into TQ management on a downshift?

Log, tune, and photos attached.

Thanks in advance.

1876418765

joecar
August 29th, 2015, 04:07 PM
Look like the 2/4 band is slipping...

did you check level and condition of ATF...?

did you measure line pressure at the tap on side of case...?

Dannn
August 29th, 2015, 05:15 PM
Look like the 2/4 band is slipping...

did you check level and condition of ATF...?

did you measure line pressure at the tap on side of case...?


Great... Kinda weird that it hasn't gotten any worse in the last 20,000 miles (knock on wood). And i'm pretty harsh on it. Oh well, planning to swap to an 80e eventually. Just don't know how I'm gonna fit it as the rear driveshaft is only 13" long as it is.

Fluid level is good, ATF is 20,000 miles old. Looks good and clean, no nasty smell.

I'll check pressure tomorrow. I'm assuming it should be close to the PCS pressure pid correct? Wonder if I have a spare pressure transducer laying around I can hook up and log analog voltage signal to see how close it is to the PID.

Thanks, will post soon with results.