Piston Slap: Mechanical and Chemical Solutions for Transmission Slippage

“Ed” from Ohio writes:

Sanjeev (I kid, I kid!), I was recently given a 186,000-mile 1997 Dodge Ram 1500 with a 5.9-liter Magnum V-8. Its transmission is slipping a little when reverse is engaged. The ATF is low, though it appears clean on the stick. This might be the reason for the slippage, but it also suggests a leak. (So far I have yet to see any drops of the floor from anywhere under the transmission—perhaps it’s that low).

I have a few questions: Where to start? Should I add new fluid in the hopes it solves the slip and shows me where any potential leaks might be?

I’ve read online that these transmissions have bands that can be adjusted to eliminate slip. I’m pretty technically inclined but have avoided work on automatic transmissions because, well, frankly I don’t understand how they operate. Can I do this job myself? Would it be better to take the truck to a transmission shop and have them perform a full flush?

Or is this a case of step one above, then two, then three? Thanks for any help you can provide!

Sajeev answers:

Apparently Ed is a bit of a busy bee, as he dug into the Dodge’s 46RE gearbox just a few days later:

“I delved into the automatic yesterday, replacing the filter and the shift governor solenoid. I carefully tightened the rear band adjustment bolt down, and then backed it off as directed. The problem is that the bolt you’re supposed to torque is an 8mm square bolt, and a regular socket won’t do. I can’t say I got proper torque on it, but it does not slip anymore, but on the opposite end of the spectrum, it also doesn’t grab too hard when shifting into reverse.

I’ll have a shop check my work, and that should help further flush things anyway. But now I have a truck shifts appropriately into gear, and after a brief drive everything appears to work as intended.”

Whelp, sounds like you did the adjustment correctly! Apparently over-tightening the bands can make the transmission feel like it’s dragging or binding, but let’s hope that isn’t the case. That your drive went well should answer all your questions.

At that mileage, your truck might already have a rebuilt transmission, or perhaps that’s the original unit and it had an easy life with a lot of highway miles. No matter the backstory, you likely extended its life by adjusting the bands and doing a fluid service.

But at that mileage, if it hasn’t been subject to appropriate service intervals, sometimes fresh fluid is worse than the stuff that came out of it. Friction material from clutch packs often finds itself inside old ATF (automatic transmission fluid) and is literally the glue that holds a gearbox together. If this happens and your gearbox is officially on borrowed time, well, I have a potential solution for you. Or at least a decent band-aid to squeeze a few more miles out of it.

Consider adding a bottle of Lubegard red if the Dodge is still shifting a little funny. (Remove ATF if needed, as you never want to overfill a gearbox.) If you think anything sold in a bottle is nothing more than snake oil, well, I used to feel that way too. Put another way, I am a decades-long Lubegard customer and they’ve never given me a dime in compensation for doing so.

I only learned about this additive when the Internet told me it was the solution mentioned in a Ford technical service bulletin for harsh transmission engagements. Whatever Ford put in there back in 2006 certainly worked, to the point I used Lubeguard Red in other Fords when they started misbehaving.

Over the summer I added Lubegard Red to my uncomfortably beloved 1989 Lincoln Continental with its awful tragically flawed AXOD transaxle. This was a last-ditch effort to address the 1-2 upshift shudder and harsh reverse/drive engagement that’s so common in these wretched little gearboxes. After 100 miles of circulation within relatively new ATF (and a new filter), gear engagement is now buttery smooth and silent. The 1-2 shudder happened just once, which is significantly better.

But nothing’s truly perfect: Lubegard products seem impressive for gearboxes with minor issues that have yet to turn into fatal flaws. Just make sure to use the right product for your gearbox, especially if you have a CVT. But thanks to their “red” formulation, I no longer “shudder” to think about my transmission issues. (Famous last words, am I right?)

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