Engine/Transmission (1994 - 1998) Flexplate going south?

[Hummin Cummins]

I have devoloped a serious rattle / vibration as of late. It only shows up when the truck is running and in gear, only when stopped or idling along slowly. It does it in both forward and reverse gears. It almost sounds like a knock, and can be felt in the floorboards. If I put truck into neutral it goes away, pull it into drive and it starts seems like it gets worse if I manually pull it into 1st. (done while sitting still) I had the inspection plate off and saw no metal filings around the t/c area and checked the torque on the t/c bolts and all were good. Could it be my flexplate is cracked and ready to fly apart? It smooths right out once up to speed. I put the truck on jackstands and with it running in neutral the rear wheels turn, is that normal?



Hope someone can help me find it. Pulling the camper to Kentucky Speedway next weekend.



Chris

 

[Hummin Cummins]

Bumpity bump

 

[GAmes]

When mine went bad on my 92 it only made noise for about 5 to 10 minutes, then the center broke out :{ . Fortunately I was still in warranty and only about 5 miles from a Dodge dealer. It is the only one I have ever seen break, but I would think that if yours is cracked then it wouldn't be long till total failure. One more thing on edit. It made noise in nuetral too.

 

[Hummin Cummins]

Thats what has me baffled. Mine only makes noise in gear and thats the location we have chased the noise to. Been like this for a few weeks now. I thought something would have left go by now.

 

[Hummin Cummins]

Well after further checking, it seems that the knock/growl/grind whatever the heck it is gets louder if I manualy pull the gear selector down into low 1. I notice it sometimes too when shifting from park. If I pull shifter out of park slowly it seems to do it then too. Gonna check the shifter linkage adjustment. Any other ideas? I really dont want to take a ride on a wrecker on my trip to KY. and dont want to pull the transmission to look at flexplate, if I go in that far I'm gonna replace it while I'm there.

 

[Hummin Cummins]

Well, it's definately in the flexplate / torque converter area. I unhooked the shift linkage, blocked the wheels and shifted it from underneath. I still see no metal filings anywhere, but there is noticable wobble in the flexplate. Should there be enough movement there to see with the naked eye while the engine is running? How much of my transmission is this going to hurt until I can get a flexplate shipped (everything has to break on a holiday... lol)

 

[Joe G.]

I had a flex plate fail. It had no warning sound. It broke and then it made a lot of racket. There should be no observable motion at all that you can see when it's running. When mine failed it also took out the transmission pump. If it fails, a wrecker is the only way you will get it to move. I don't think you will see any filings. It's more of a metal fatigue kind of thing that causes it to crack away from the hub. You could remove the screws that fasten the flex plate to the torque convertor. Inspect the holes with a mirror to see if they are round or misshaped or have cracks around them. If you can make any forward or backward motion with your fingers on the flex plate after all the screws are removed then it's shot and has to be replaced. You should be able to rotate the engine with a large screw driver in the ring gear with no trouble. If there are any cracking sounds when you try that it's in bad shape. If it's bad don't drive the truck.

 

[Hummin Cummins]

Thanks Joe.

Talked to my brother in law this morning (certified cat mechanic) He's sayin its the flex plate. Said hes not sure about the lil cummins engines but with the bigger cats extended idling can cause the cracking due to harmonics. I have at least 1/8" of movement (wobble) when idling and a little more when in gear. Gonna call Piers and get one overnighted hopefully can have it in before my KY trip.



Chris

 

[Joe G.]

You should avoid starting it until you replace the flex plate. That wobble is transferred to the TC. That's hard on the front seal and the pump bushing.

 

[Hummin Cummins]

Ok I wont drive it, got too much in this transmission to ruin it.

Thanks again. Any seals easily replaced up front while I have it out?

 

[Joe G.]

The front seal is easy to replace with the TC out. You probably should replace it. If you have a service manual it has all you need to know. The pump bushing is a PITA to replace. If it were me I would replace it, but I will not advise you to do that unless you or someone you know has experience with the transmission. It may be ok.