Torque converter shudder

RLJL0582

MEMBER
2008 DODGE MAGNUM
2.7L
6 CYL
2WD
AUTOMATIC
119,000 MILES

I have done much research into the issue, but would like to get some input as my symptoms are similar, but not the same as others I have read thusfar. I own the car listed above with the 42rle transmission. I have owned the car for about two months and have only had to replace the typical worn out suspension parts due to clunking. The recent issue that has just shown up over the last week or so is a shudder when the car is around forty mph. It happens everyday almost like clockwork. I will try to be as detailed as possible. The first startup of the day I leave my house and drive roughly two to three miles at which time I stop at the local convenience store at which time I shut the car off. A few minutes later I leave the store and get around a mile or two down the road when the shuddering begins. Like I said it is always around forty mph. The shudder lasts only a minute or two then eventually stops and does not return until the same time the following day. At first it was intermittent but does seem to be getting worse as today it began shuddering within a mile of my home between twenty five and thirty mph cruising through my neighborhood which cleared before I got to the store, but shuddered again in within a mile of leaving the store this time which again cleared a few minutes later and did not return for the remainder of the thirty mile drive. When leaving work on the reverse path home the car operates perfectly without issue everyday. I did try adding 4oz of Mopar LSD friction modifier that I read was recommended in other posts, and seemed to work for about a day although there was a shudder just much milder but reverted to the original condition the following day and has remained. Should I try adding more friction modifier? What should my next step be?

I forgot to mention I did check the transmission fluid level and it was correct and pink in color.

Will a TCM reprogram fix this? It seems that it runs fine until the EMCC is active. This is when it appears to have the shuddering issue. This is the link I found during my research that makes me think the EMCC is causing the issue: 42RLE poor performance.

2 Replies

CARADIODOC

MECHANIC
33,742 POSTS

You have the wrong transmission fluid. My 1994 Grand Voyager does this too.

All of the great clues and observations you listed are the same as for my van. Chrysler, which is famous for developing innovations since the 1950's that benefit their customers, as opposed to GM's innovations that benefit GM at the expense to their customers, invented the lock-up clutch for the torque converter starting with some 1976 models. That is designed to eliminate the slippage that allows the engine to remain running when the transmission is in gear and the car is stopped. That clutch is just there to improve fuel mileage.

All torque converter clutches engage between roughly thirty five to forty five mph, only in the higher gears, only once the engine is warmed up, and only when you are not at wide-open-throttle or applying the brakes. It is springtime, so you have to drive a shorter distance before the engine reaches the temperature at which the clutch will engage.

To prevent an uncomfortable clunk when the torque converter locks up, it engages gradually. It is supposed to slip a little around thirty five mph and it will be fully-engaged by around forty five mph. The shudder you feel is from the clutch grabbing too hard, engine torque breaks it free, then it tries to lock up again, in rapid succession. The way to prove this to yourself is when the shudder occurs, hold the accelerator pedal and road speed perfectly steady, then lightly tap the brake pedal. The computer sees the brake pedal as you're planning on coming to a stop, and in preparation for that, it unlocks the clutch so the engine does not get snubbed off. The shudder will stop occurring, then start again two or three seconds after you release the brake pedal.

Do not waste your money on additives in a can. If it was that simple, we would all be doing that. You need to have a standard, simple transmission drain and fill with a filter change. That will replace about half of the fluid which is enough to replenish the required additives. If you have this done by a Chrysler dealership, they will know the correct fluid to use. If you have this done at an independent shop, be sure to tell them it is the shudder that needs to be addressed. Most will know the correct fluid to use, but there are still a few people out there who are not aware of this.