68RFE Shift Issue?

**swanitalia** · 1 Week Ago

Hello all.

Late last year, I had my 68RFE in my 2008 Dodge RAM 2500 rebuilt.

Since then, every once in a while, the 4-5 and 5-6 shifts have done something unusual.

The weird shift feels like a miss-shift to me, especially the 5-6 shift.

The shift is so violent and feels like it locks up the rear wheels.

It has even chirped the tires and felt like I slammed on the brakes.

The transmission is still under warranty so that I will be taking the truck in.

However, I just wanted to see if anyone has seen or heard of this issue happening before.

Regarding the transmission, in 2022, I installed a Randy's Babymaker 1000 and a RevMax-tuned TCM (from Gibson Diesel).

The transmission worked great until Oct 24, when I got a P0740 code and ended up taking it to a local diesel performance shop.

They went through it, rebuilt it, and installed a twin disk converter.

The transmission felt a little weird at first, and I noticed the fluid level was low, so I topped it off.

The weird shift was also present, and one day I saw the shop owner in the store and asked him about it.

He said it was the twin disk converter locking up, and it should get better once the transmission completes its learning.

I've been at about 5k miles since the rebuild, and with the warmer weather, the weird shifts are occurring more often.

Over the weekend, it occurred when I was merging onto the highway and nearly caused an accident.

So far, I have done a quick relearn, drive relearn, and checked the fluid.

The transmission never goes over 180°F, so it's not overheating.

I may put my stock TCM back in the truck to see if it's a TCM or tune issue.

The reason I'm checking into it now is that I have a big trip in two months and want to figure out the issue before then.

Thanks for the input,
-Swanitalia

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**sootmaster** · 1 Week Ago

Hello, friend.

This description is not good!

I would suspect that if HOT, I would monitor speeds and gear applied.

I put a Trans Diag in the DRIVE TRAIN Tab here so I can see the applied chart of what clutches are applied.

In-depth so that you can know more about the 68RFE.

I suspect that there is cross-leakage in VB and the main plate.

Scan Tool to see the INPUTS and OUTPUTS, like TQ Apply% % and Loads, Gear Commanded.

If you don't know or trust the last builder, I would recommend having another shop test the unit.

When you have a Slam or chirp tire brake, the feeling could be that of two or other clutches being applied, or one that is not wanted.

Only going to get worse or break; not normal.

Stop driving and let them drive!

Or have other shops test?

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**swanitalia** · 1 Week Ago

SootMaster, yes, this only occurs when the transmission is hot.

When it's cold, it shifts perfectly.

Looking up the symptoms of a cross leakage in the VB, it sounds like that could be the issue.

I forgot to mention in my original post that sometimes the 4-5-6 shift feels like the converter slips and doesn't lock up.

I will be dropping off the truck at the shop today so they can inspect it.

I kind of regret going to this shop over another shop that is known for its Cummins work, DNR Customs.

If the shop can't make it right, I'm going to DNR.

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**sootmaster** · 1 Week Ago

Cross leakage in a VB or Main shaft sealing ring, where hydraulic pressure enters another clutch.

These are clutch-to-clutch transmissions; adding another would be suspicious.

Can be VB to Case or VB separator plate leakage and torque, main shaft, OD Input assembly cracked, and so forth.

I do not see a tune or module issue when viewed in past trans builds, but I will need to scan and pressure test with manual gauges to trace the root cause.

Stop driving and testing; it will not be cured by having truck weight, and may destroy your unit.

Can I send a message to the forum when a 68RFE is not working?

STOP STOP driving!!

Test on JACK STANDS!

Never use the weight of the truck to test.

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