Wrangler 392 & Grand Cherokee SRT tune. Nashville.
The 392 Hemi doesn't care whether it's sitting between solid axles or driving all four wheels of a Grand Cherokee - it responds to a tune the same way every Gen-3 Hemi does. We run the same playbook here that we run on the Scat Pack: wake up the throttle, rebuild the shift calibration, delete the MDS shudder, and hand it back the same day. For Wranglers on 35s or 37s, we fix the speedometer and shift points while we're in there. $799, flashed while you wait.
Every Carma tune includes.
Real prices, no dyno-number runaround. Here's what comes with every flash — at no extra charge.
What we do for the 392 Jeeps.
Stage 1 on the 392 is a full calibration rework, not a canned file - timing and fueling optimized for 93 octane, throttle response sharpened, MDS deleted, and the eight-speed's shift calibration rebuilt alongside the engine so the whole drivetrain moves together. You're in and out same day. If you add mods later, the re-flash is free, and if you ever want stock back, that's free too. Your booking deposit is refundable up to 48 hours out.
Both of these run the same 6.4 we tune in the Durango SRT, so the platform has zero mysteries left for us. If your PCM is 2015 or newer it shipped factory-locked - we handle the unlock in-house for $350, same visit, no mail-order wait. Wranglers on 35s or 37s get tire size and gear ratio written into the calibration so the speedo, shift points, and traction systems all agree with reality again, and tow logic stays untouched on both trucks. When you're ready to chase real numbers, the classic Hemi path still works: intake, exhaust, then CNC-ported heads cut in-house with a custom calibration on top.
- Same-day Stage 1 flash - $799
- Locked 2015+ PCM unlocked in-house, $350
- MDS cylinder deactivation deleted
- 8HP75 / 8HP70 shift calibration included
- 35 / 37 tire and gear recal for Wranglers
- Free re-flash with new mods, free return-to-stock
Pricing for the jeep wrangler 392 & srt.
Mods we pair with this tune.
Stage 1 needs nothing bolted on first - it's worth the $799 on a bone-stock Jeep. But the 6.4 loves hardware, and every mod below comes with a free re-flash so the calibration always matches what's actually on the truck.
- Cold air intake — More airflow up front - we adjust fueling so the Hemi actually uses it instead of fighting it.
- Cat-back or mid-muffler delete — The 392 exhaust is corked from the factory - this is the cheapest sound-per-dollar on the platform.
- Long-tube headers — The biggest single bolt-on gain on a 6.4, and the point where a custom calibration starts earning its keep.
- 35s or 37s with a regear — Wrangler-specific - we write tire size and axle ratio into the tune so speedo, shift points, and torque delivery all match.
- CNC-ported Hemi heads — Cut in-house on our machines - the ceiling-raiser for when bolt-ons stop being enough.
No dyno-number games, no hard sell. Drive it, and if the tune isn't for you, we revert to stock at no charge. That's how confident we are in the map.
Common questions.
My 392 has a locked PCM - what does that mean for tuning?
Every 2015-and-later Jeep and Dodge PCM ships locked, and yours is no exception - it has to be unlocked before any tune can be written to it. We do the unlock in-house for $350, same visit as your flash, so you're not shipping your computer off and waiting two weeks. One trip, unlocked and tuned.
What does the MDS delete actually fix?
MDS drops the 392 to four cylinders under light load, and on these trucks it shows up as drone and a shudder right in the cruising range - and the MDS lifters are a known Gen-3 Hemi weak point besides. Our Stage 1 disables it entirely, so the engine runs on all eight all the time. Smoother cruise, no four-cylinder drone, one less thing cycling in your valvetrain.
I put 37s on my Wrangler 392 - can you fix the speedometer and shifting?
Yes, and it's included in Stage 1. Bigger tires throw off the speedometer, the odometer, and the 8HP75's shift points, so the trans hunts and short-shifts because it thinks you're going slower than you are. We write the correct tire size and axle ratio into the calibration so everything reads and shifts right again.
What do you change in the transmission calibration?
The Wrangler 392 runs the 8HP75 and the Grand Cherokee SRT the 8HP70 - both excellent boxes strangled by soft factory shift schedules. We firm up the shifts, cut the torque-management dip between gears, and stop the constant hunting on grades. It feels like a different transmission without touching a single part.
I tow with my Grand Cherokee SRT - does the tune change that?
No - we leave the tow logic intact on both platforms. Tow behavior, thermal management, and the transmission protection strategies stay exactly as Jeep built them. You get the extra power for pulling grades without giving up any of the towing safeguards.
Can you dyno my Jeep? They're both four-wheel drive.
Our chassis dyno is 2WD-only, so a full-time 4WD Wrangler 392 or AWD Grand Cherokee can't strap to it for pulls. That doesn't matter for Stage 1 - it's a proven flash, not a dyno session. For custom work on these platforms we verify with street data-logging instead, which honestly tells us more about how a 5,000-plus-pound Jeep actually drives.
Does the tune mess with 4-Lo or off-road drivability?
No. Low-range throttle mapping and crawl manners stay stock, because the last thing you want on a rock ledge is a hair-trigger pedal. The sharper response lives in the street calibration, and everything Rubicon about your 392 stays Rubicon.
Book your Jeep Wrangler 392 & SRT tune.
Drop it off in the morning, drive it home tuned by end of day. 1035 3rd Ave S, Nashville, TN 37210 · Mon–Fri 8 to 5.