Resolved!!! 68rfe 6th Gear Shutter after Valvebody Rebuild

[Wvmountaineer87]

Just finished installing the BD protect68 kit and ATS accumulator pistons in my 2020 Ram 3500 mega. Install was easy/straightforward. I used the BD gasket plate and a set of billet accumulators from ATS, along with the overdrive shim (washer) from Sonnax, added a BD Diesel deep sump pan and filled with Castrol ATF+4. I’m running in “race mode” +150hp. Trans tuning to allow up to 250 psi trans pressure.
THE PROBLEM!!!
Everything is great while I’m running through the gears, and even downshifting feels fine… but… while cruising in 6th gear little to no throttle, the truck will surge or jump or sputter or hesitate… whatever you wanna call it. It only does this in 6th gear no throttle or barely on the throttle. If I get into it it stops. Happens at any speed in sixth but is most noticeable around 70mph and 1500 rpm. Digital gauge shows converter is locked and not slipping.

****The truck doesn’t do it on “street mode”
+120hp and 160-170 max trans line pressure. I’m seeing about 100psi trans pressure cruising with this setup, and with the new setup I’m seeing 200. New setup also has LBF.

Truck is leveled with coils and I’m running 37x13.50x18 tires.
The only other modifications are an AFE intake and a pusher intake elbow.

Thoughts???

 

[Dwilly]

Mine on 37s does this also. It's like a rapid on-off feeling that you can really feel. Seems to only do it after I crest a small hill and start downwards. Just for a few stutters. Mine is a stock transmission. I always figured it was the truck protesting heavy rims and 37 MTs.

 

[Wvmountaineer87]

Mine on 37s does this also. It's like a rapid on-off feeling that you can really feel. Seems to only do it after I crest a small hill and start downwards. Just for a few stutters. Mine is a stock transmission. I always figured it was the truck protesting heavy rims and 37 MTs.

I’ve ran 37s for about 25k miles and haven’t experienced this until the new trans parts were installed and I added the power and trans pressure.

 

[Brewbud]

Mine on 37s does this also. It's like a rapid on-off feeling that you can really feel. Seems to only do it after I crest a small hill and start downwards. Just for a few stutters. Mine is a stock transmission. I always figured it was the truck protesting heavy rims and 37 MTs.

I don't have this with 37s on the stock 68RFE transmission.

 

[H3LZSN1P3R]

Have you run the tune prior to the trans work? I would not be surprised if its just a bad tune

 

[Wvmountaineer87]

Have you run the tune prior to the trans work? I would not be surprised if its just a bad tune

Same tuner for the previous street tune, new race tune was flashed when I installed the trans parts and that's when I noticed the issue. I switched back to the street tune and it doesn't do it anymore. Tuner is thinking its a rail pressure issue.

 

[Wvmountaineer87]

Actual fuel rail pressure is anywhere from 700-1000 psi higher than desired pressure when it happens

 

[Wvmountaineer87]

After data logging it looks like the shutter occurs when the trans pressure drops abruptly from 240ish down below 200 and immediately goes right back up. It will jump back and forth the entire time coasting in 6th gear.

 

[Wvmountaineer87]

Still no resolve. I’ve changed the pressure sensor, pulled the Valvebody and installed new filters and the surging is getting worse every time I drive the truck.

 

[Wvmountaineer87]

Resolved!!!!!!
After hours and hours of trial and error, my issue is resolved!!!
It was in fact a tuning issue. The underdrive was pulsing on and off. This is a known issue on 2019+ trucks. Be very selective on who you choose for tuning, especially 68rfe tuning! New trans tune fixed all my issues and I decided to trade it in! I hope whoever buys it enjoys the fruits of my labor hahaha!