Funny problem with OD transmission

transmissions

#1

I hope transman618 is reading this, but all responses are welcome. I just bought a 1999 Dodge RamVan 1500, with 318 engine and automatic transmission. When I test drove it I notice a bumping at 45 to 60 MPH range which I assumed to be a wheel balance issue, but in driving it home I discovered this bumping goes away if I turn the OD off. It also goes away above 60 MPH.



So, is this the lockup converter having a problem? Is this something likely to be fixed by a solenoid pack? Any thoughts? What should I ask to have checked? I am not a big auto transmission user, so this is foreign territory for me.


#2

Would love to know the answer to that myself. I have an 04 Grand Cherokee that does the samething. Dealer was know help at all, all the dealer can tell me is that if it’s not throwing any codes out everything is OK and they wouldn’t know where to begin looking for the problem. Someone did suggest that it could be a vacuum leak somewhere.


#3

Its very possible that it is the converter falling in and out of lockup. (Not uncommon). Does it feel like you are driving over a washboard or does it feel like a slight surging??

I would start diagnosing this one with a scanner (NOT a code reader) by monitoring the transmission functions and the lockup command from the computer.

Same thing for you, Ranger. It doesnt have to throw a code for there to be something wrong with lockup.

transman


#4

Thnaks transman. As stated in the first post, if it is the lockup converter would taking it out of OD smooth out the ride or would it still act up? I haven’t tried driving it without the OD off.


#5

It feels more like a slight stumble.


#6

No, taking it out of O/D will not cause it to stop because when you lock out O/D, the converter locks-up in 3rd gear.

transman


#7

A scan tool should give you the answer… You could try driving the vehicle with your left slightly on the brake pedal… This should signal the trans controller to release lockup. If if the noise is gone “maybe” the converter. Remember with the lockup bypassed you have less of a load on the vehicle…


#8

Lock-up torque converters often develope problems which can be successfully treated with service and additives. Change the fluid and add one of the many products which advertise improving lock-up clutch chatter problems and hope for the best or get a rebuild or drive in 3rd.


#9

On mine, it feels more like a washboard than surging. I really thought it was a wheel out of balance at first.

I’ll have to find a reliable transmission shop to have this checked out. Fortunately the service this van is going to see will be mostly around town, low speed, stuff. I was planning to have the transmission fluid and filter changed out ASAP anyway. We’ll see if that does anything.


#10

Thanks for the encouragement. I will be changing the fluid and filter soon, so will look into additives and/or possibly RedLine or other synthetic that might help.


#11

I tried the left foot(lighty) on the brake pedal cruising at 65 on the interstate today. Noticed no difference at all. Tach stayed the same. Should the RPM’s have jumped up a little?