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Modified JK TechTech related bulletin board forum regarding subjects such as suspension, tires & wheels, steering, bumpers, skid plates, drive train, cages, on-board air and other useful modifications that will help improve the performance and protection of your Jeep JK Wrangler (Rubicon, Sahara, Unlimited and X) on the trail.
PLEASE DO NOT START SHOW & TELL TYPE THREADS IN THIS FORUM
They are alive for now. Not sure whether the 392 V8 Jeep will lead to a 5.7 Hemi powered one which is more of a 4x4 IMO. Would obsolete both the V6 and eventually hurt people like Robbie at Motech. But the new Chevs sure juice up the Jeeps but sure cost a lot to do even doing it in kit form. And one will gain fuel mileage comparing the same driving habits before and after. I got 10-15% over my 3.8 and I am going to play with tuning for more economy. I agree with Turbo_Geoduck and that is it is good to see them conversions still popping up.
MoTech Gen V 2019 L83 5.3L With 8L90 Transmission Experience
MoTech installed a 2019 L83 5.3L engine and 8L90 trans into our 2010 JKUR in May 2020 and we really love this drivetrain. Robbie said this would be the first 2019 L83 they installed into a pre 2012 JK so some problems were expected but they were minimal. We shipped the JK to them in mid April. They only missed the planned delivery by one week even with all the problems of the pandemic. He didn’t really want to turn it over to us at that time since he found out that the 2019 TCM was locked by GM and he couldn’t program it until he had sent it in to get unlocked by HP but we were on our way to spend the summer in the Rockies and needed it then. We did get the aluminum dual pass radiator, the Camaro fan and the Aero Force gauge in the package.
Toward the end of May we drove to Las Vegas and test drove the JK and we were really blown away by the power and acceleration it had. We tested it in 4 low since Robbie had to change out the 4:1 Rubicon for a 2.73:1 transfer case. Everything but the tap shifter worked and Robbie explained that he was waiting for the reprogrammed/unlocked unit from HP.
He shipped the JK to us and we tried it out on the Miller Jeep Trail along with our daughter’s family in their JK and it performed great except for the tap shift’s not working which was kind of scary on the steep downhills. I then fitted and installed our Rock Hard engine skid plate before leaving for the Rockies.
Robbie shipped the new TCM to me as soon as he got it and the install was very easy. I did find out that the 8L90 really does need to be trained. Some exciting shifting going on for a couple of days but then it settled in and works fine. The tap shift works really well and the first gear combined with our 35s and 5.13 gears really holds it back on the steepest down hills on the trails we run (Red Cone). One thing we learned is the engine/trans speed matching in the TCM can be exciting when starting a step descent in 2nd and tapping down to 1st. It lunges so I have to remember to have my foot on the brake when doing this.
The engine has so much torque right from the start that the only reason I need to shift into low range is so I can engage lockers or go down steep grades. I no longer have to follow slow 18 wheelers up the 10,000’ passes in the Rockies as we did with the 3.8L. This thing really flies past them. When getting on it from a dead start on dry asphalt it will chirp the 35’s until the traction control takes over. I don’t try that very much as we have the 44 axles and don’t want to stress them. It has a nice V8 sound that is pleasing to us but not too loud. It is a real pleasure to drive both on and off road. Just put it in drive and go. The transmission does a great job of staying in the power band of the engine and won’t upshift to too high of a gear when going slowly on the dirt trails or climbing hills. I am glad to have the Aero Force gauge so I can tell what gear the trans. is in.
The 3.8L stock engine had a bad habit of drinking oil, about 500 miles per quart and had no power for highway driving. Even on a flat freeway it would have to downshift just going over overpasses and had trouble doing 60 mph in a strong headwind. I must say that it was one of the best off road, low range engines we have owned though. We didn’t drive it in the dunes as we knew it couldn’t spin the tires trying to climb them.
I have kept an eye on the trans and engine temps while wheeling and don’t see any problems at all. The highest I saw the trans. temp while climbing a rocky trail for 2 hours in low range was 230 deg. F. That just about matches the highest engine temp I noticed also. The fan doesn’t run very much even with the A/C on. Robbie said to expect to see engine temps in the 230 deg. F range with this engine.
After 7,000 miles we are getting the same mileage that the 3.8L gave us. No better or worse. We measure every drop of fuel put into the JK and track the miles driven in a spread sheet. That’s 9,384 gallons and 121,000 miles. With the 5.13 gearing, 35” tires, Rock Hard bumpers, racks and full skid plates and a lot of tools it weighs 5875 dry and we get 12.7 mpg. We don’t drive it except to 4 wheel so a lot of the miles are on dirt and in 4WD with the tires at 12#. I don’t pay any attention to the computer readouts that say I am getting 40 mpg going downhill or one tank computations that tell you you get 18 mpg on the level ground freeway. They don’t tell you anything about cold warm ups or waiting on the trail for the vehicles in front of you to clear obstacles or the group of wheelers coming at you to go by on the narrow trails or running the engine while airing up the tires at the end of the trails. We run 85 octane at 8,000+ feet in the Rockies and 87 octane at the lower desert elevations with no problems. It runs fine. I am satisfied with the mileage.
Robbie didn’t have time to mess with our Rock Hard engine skid plate so I took care of it when we took delivery of it. The modifications were minimum with just a little cutting with a 4.5” grinder and now we have all 3 skid plates as we did before.
The problems we found with the installation were: the intake manifold on the L83 is quite high and the throttle body points skyward so hood clearance is an issue. MoTech cut out some of the hood ribs and made a bracket to hold the intake tube but the flexible tube rubbed slightly. There was a slight problem with the A/C lines blocking the driver’s rocker cover oil fill cap and a slight leak in a radiator plug.
We made arrangements with Robbie to visit MoTech in October on our return and he worked us in even though they are really slammed with projects. They went way out of their way and took care of all the items that were bothering me and more that they discovered while looking over the installation. They made a new air tube mounting bracket to lower it so it clears the hood and made up new A/C lines to clear the oil fill cap. Robbie touched up the tune on the ECM and TCM for us and reworked the exhaust mounting brackets that they said might need more support. I have never had such good treatment as I have with Robbie and Motech. I am really pleased with their service and work.
We certainly recommend Robbie and MoTech as great to do business with.
Here is a link to the video Robbie made of our JK’s test drive.
Rick, exactly what I would say about Robbie, Motech and my conversion being exactly like yours. I did mine myself using the Motech kit. People ask what it is like and my response is "like Chev designed this transmission for the Jeep" as it is almost made for our vehicles. I have a 2016 setup so got the T87/E92 ECUs. Only difference mine has from yours is I vented the breathers on the valve covers out through tiny K&N filters into atmosphere to reduce the carbon buildup on the intake valves. My engine had 16000miles on it so I have put 10,000kms on it in the last 7 months so guessing this is going to last me for a long time. Your write up is almost exact to what I would say. One fellow here, on the forum, from Arkansas used the 6.2/10speed so that must be incredible power wise. To others procrastinating I say go for it. And the 5.3 is all you need unless you are a speed/power freak.
11-24-2020, 05:35 PM
