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Discussion Starter #1
Hi Folks

I writing this because I am at wits end with a problem with the Auto Transmission on my

2010 RT. I have had the car for about a year and love it but recently something has happened

with the drivability of the tranny. The car is my daily driver and I live in the NYC metro area

so I deal with a lot of traffic and stop and go driving. I never had a problem with how the car felt

while upshifting and downshifting until I changed the exhaust. I put in a Solo system about 6 weeks

ago and now I can feel and hear every shift. Now here is the problem, the tranny seems to be

constantly searching to be in the correct gear, upshifts are unpredictable and the downshifts

are too hard (when on the highway, if I take my foot off the gas just for a moment. the car downshifts

very hard). I went to the dealership and they reflashed the pcm/tcm with the latest updates, that did

very little. So I bought an Intune and put on the 91cai and that also did very little for the again

the drivability from the day to day ..I just puzzled if this is just the NAG-1 tranny doing its

thing or if there is an issue, I am at a point that I simply don't enjoy driving the car anymore..
 

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This is all that I could come up with:
Early NAG1 transmission valve bodies, prior to about 2010, are known to develop a leak in one of the regulating piston’s cylinders. This causes confusion in the transmission during shifting where at the shift peaks the RPM just kind of plateaus momentarily.
Also the NAG1 is extremely sensitive to fluid levels mainly due to its unique, and odd, method for determining transmission overheating. In the middle of the valve body is a little floating piston valve. As the transmission fluid heats up it expands raising the fluid level in the pan. If the fluid gets too hot and expands too much the floating piston valve rises up far enough to contact its valve seat and closes which signals the transmission controller that it’s overheating and the TCM goes into limp mode. So over full is very bad unless you like limping home.
Check to make sure that the exhaust isn't frying any of the wires going into the transmission.

Otherwise good luck as that's all that I have for you.
 

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And....
Conversely, the NAG1 hates low fluid levels and can be damaged fairly quickly if the level is too low. So under full is very bad. But you can’t just stick a dipstick into the transmission and see if you need more or less fluid. Mercedes calls for a special tool made by Miller, part number 9336A. This special dipstick is marked in millimeters and to use it you need the temperature/fill level chart from the service manual (or find it online) and you need to know the exact temperature of the transmission fluid.
 

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I would put the stock exhaust back on and see if the problem is still there, by putting on the solo exhaust you have changed velocity and back pressure. If you own an R/T without STP you have 2 1/4 pipe with 2 restrictive mufflers and resonators and the new exhaust has changed air flow, HP and torque which could relate to how your trans is acting. You could actually be losing HP and that could be affecting shift points.
 

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Discussion Starter #7
Guys thank you very much for the advice, I do have the MDS off and I have reset

the tcm adaptives with little effect. DeathStar I will go to the dealership and have

them take a look at fluid levels and check for leaks in the valve bodies. Everything

has changed the minute I put on the Solo exhaust, my next question is, with so many

people changing out the exhaust system in these cars, wouldn't more people have my

problem, driving in the city is where I really notice it, the tranny always seems

sluggish and confused and downshifting is an adventure..I can deal with it on the

highway..even then downshifting is abrupt... If changing out the stock exhaust to

more free flowing system causes this wouldn't everyone has this issue.. finally

whats everyone's opinion of a stage 2 valve body kit from speedlogix, would that

help for a daily driver with little mods
 

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09 RT Challenger auto
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And....
Conversely, the NAG1 hates low fluid levels and can be damaged fairly quickly if the level is too low. So under full is very bad. But you can’t just stick a dipstick into the transmission and see if you need more or less fluid. Mercedes calls for a special tool made by Miller, part number 9336A. This special dipstick is marked in millimeters and to use it you need the temperature/fill level chart from the service manual (or find it online) and you need to know the exact temperature of the transmission fluid.
There is a thread in here somewhere. We use a nylon zip tie and go down the what used to be the trans dip stick tube. The cap will twist off once the plastic pin is sheared during removal of the cap/

Motor and trans running temp of 190 200 its 72mm up the stick and dead cold its 20mm up the stick the stick going to the bottom of course and in Park.
I checked and marked mine once SHR built my trans and I got home. almost 3yr ago, with hundreds of passes.
Double check but the factory has it at 75mm on the stick I think it is, dont reall need "the tool"

Wierd it all went once the exhaust changed though. Good Luck
FlatTop
 
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