3.92 Downshift stumble?

mrmagoo_83 · Feb 22, 2017

Previously drove an 06 Hemi, just recently bought a new 16 hemi 4x4 Sport with a 3.92, so I'm not sure if it's me adjusting to the new truck or something wrong. I had a loaner the last two weeks that had a 3.21 and I saw none of the same behavior that my truck is having.

I've noticed taking off is sluggish unless getting on it good. But what really is bothering me is when I'm coasting. It seems as I slow to around 20mph and the tranny downshifts, I assume to second, the truck feels like I just tapped the breaks. It's enough to move you in the seat a little. At first it scare me enough I thought it was about to stall or something and the person behind me was a little too close and nearly rear ended me due to the sudden deceleration.

Hoping this is normal and I just am not used to the new truck or someone knows what it is.

chopperman1 · Feb 22, 2017

Definitely lots of unneeded (in my opinion) downshifts that happen with the 8-speeds. The one I hate the worse is when you are doing a nice slow stop and it decides to downshift and push the truck forward a bit. When I get a chance I am going to bring by my dealership and see if there are any software updates for the shifting issues I see.

mrmagoo_83 · Feb 22, 2017

OK, I'll have mine take a look as well. I just forced them to give mine back today after having it nearly two weeks to fix some minor items from my initial walk around. I still have to take it back to get the work finished while I'm out of town, so I'll add it to the list.

I've only got 2300 miles on it, so worried it was an issue that might cause damage long term.

TRCM · Feb 23, 2017

Remember, higher gearing will make the engine braking effect of the downshift feel harsher......3.92 vs 3.21 on a downshift would require the engine to be spinning 22% FASTER to not feel the braking

dRAMbuie · Feb 23, 2017

mrmagoo_83 said:
I've noticed taking off is sluggish unless getting on it good.

Definite problem here. A Hemi with 3:92's is not sluggish at all.
On wet roads I actually have to feather the gas pedal to avoid spinning the tires from a dead stop. The thing's a rocket off the line.

Did you buy the truck new or used?
And has it been hooked up to a tuner at some point?

mrmagoo_83 said:
But what really is bothering me is when I'm coasting. It seems as I slow to around 20mph and the tranny downshifts, I assume to second, the truck feels like I just tapped the breaks. It's enough to move you in the seat a little. At first it scare me enough I thought it was about to stall or something and the person behind me was a little too close and nearly rear ended me due to the sudden deceleration.

Hoping this is normal and I just am not used to the new truck or someone knows what it is

The more significant downshift during deceleration is normal for that truck (and it's actually a good thing for a lot of reasons), but what you're describing sounds extreme.
Either you're exaggerating just a tiny bit, or your truck sounds like it has some issues.

Might not be a bad idea to take it in and have the dealer check it out.

mrmagoo_83 · Feb 23, 2017

Brand new from the dealer, had about 700 miles on it.

I have to have the little things finished so I'll have them run diagnostics on the tranny while it's the. Thanks for the response.

EJR_3 · Feb 23, 2017

mrmagoo_83 said:
Brand new from the dealer, had about 700 miles on it.

I have to have the little things finished so I'll have them run diagnostics on the tranny while it's the. Thanks for the response.

700 miles seems high for a new truck. Maybe the computer adjusted to all the crazy test drives and have you get used to you. If it doesn't iron out in a few days, I would make an appointment.

Csanders1992 · Feb 23, 2017

Mine with 3.92s acted really weird at times when it was newer. Hard upshifts and hard downshifts. After the thing learned how I drive its flawless.

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dRAMbuie · Mar 15, 2017

mrmagoo_83 said:
Brand new from the dealer, had about 700 miles on it.

I have to have the little things finished so I'll have them run diagnostics on the tranny while it's the. Thanks for the response.

Just checking in to see how this worked out for you.
Did they ever nail down a problem?

mrmagoo_83 · Mar 15, 2017

dRAMbuie said:
Just checking in to see how this worked out for you.
Did they ever nail down a problem?

Actually just got it back from the dealer on Friday. They found nothing. I'll keep driving it and see if it goes away.

dRAMbuie · Mar 20, 2017

I've been told that the 8 speed comes in 2 variants. One made at Chrysler and one directly from ZF.

I'm told mine is the ZF version.

Someone else can comment on the accuracy of that, but if true, it may also lead to slightly different performance characteristics.

crazykid1994 · Mar 20, 2017

You can always pull the battery and let the computer die and let the trans relearn. My truck is a little rough on launch as it will hold first gear up to 2500 rpms when cold. Otherwise the downshifting is normal as far as I've seen. I test drove a truck with the 3:21 gears before I bought mine with 3.92 and it's definitely noticeable with the downshifts. Especially second and first gear. You get a lot of engine braking.

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mohemipar · Mar 20, 2017

My 8 speed will downshift at similar times as described but it always does it very smoothly. The only way I know is because I can feel the engine braking itself and hear the back pressure in the cat back. It never seems to over do this though, and always seems to do it when I would like it too. I very rarely feel the transmission do something it shouldnt. For the OP it could very well be the transmission still learning.

dRAMbuie · Mar 21, 2017

dRAMbuie said:
I've been told that the 8 speed comes in 2 variants. One made at Chrysler and one directly from ZF.

I'm told mine is the ZF version.

Someone else can comment on the accuracy of that, but if true, it may also lead to slightly different performance characteristics.

Just wanted to follow up on this comment for curiosity's sake.
I've since looked into it, and from what I can tell it's only the V6 Rams that have different variants of the 8psd tranny.
Namely the 8HP45 (ZF version) and the 845RE (Chrysler version).

mrmagoo_83 · Mar 21, 2017

Might have found it, but I'm getting on a plane so it'll have to wait till I get back.
The trailer brake keeps defaulting to 4.5 when I start the truck. Even though I have no trailer connected. I force it back to 0 and it seems to run like I think it should. Bit I just discovered it on the way to the airport, so not a lot of testing time.

1quick1 · Mar 21, 2017

chopperman1 said:
Definitely lots of unneeded (in my opinion) downshifts that happen with the 8-speeds. The one I hate the worse is when you are doing a nice slow stop and it decides to downshift and push the truck forward a bit. When I get a chance I am going to bring by my dealership and see if there are any software updates for the shifting issues I see.

I had a v 62014 Grand Cherokee with this exact issue that they "reprogrammed" the flash on the 8spd 3x and I still had this issue. It would disappear for a couple hundred miles then come back after it "relearns"

Thankfully my 2017 Ram w/3.21's hasn't displayed this behavior.

rocketman1083 · Apr 20, 2017

I just had my truck in for the exact same issue. 2015 Hemi with the 3.92 gears and it would feel like someone bumped me from the rear when I was at about 8-10 mph on a slow stop. I also has a CEL on for the fuel vent and they told me the two were correlated and it was supposedly the cause of my issue. The CEL was fixed but the issue didn't resolve itself and still continues. Mine didn't start until about 29k miles and was always smooth as glass before this happened. I have some replacement parts on order and have an appt with the service mgr to go for a ride to see if we can find out what's going on. Definitely a little frustrating.

Bob

RamCares · Apr 21, 2017

rocketman1083 said:
I just had my truck in for the exact same issue. 2015 Hemi with the 3.92 gears and it would feel like someone bumped me from the rear when I was at about 8-10 mph on a slow stop. I also has a CEL on for the fuel vent and they told me the two were correlated and it was supposedly the cause of my issue. The CEL was fixed but the issue didn't resolve itself and still continues. Mine didn't start until about 29k miles and was always smooth as glass before this happened. I have some replacement parts on order and have an appt with the service mgr to go for a ride to see if we can find out what's going on. Definitely a little frustrating.

Bob

Hi Bob,

Feel free to keep me updated on how your repairs and test drive goes with your dealership's service manager. I'd be happy to assist if needed, just PM our page with your VIN and let me know!

Andrea
Ram Social Care Specialist

3.92 Downshift stumble?

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