Transmission Shudder

[MRay0324]

Hello,



I have a 2003 CTD SO with the 48RE transmission. When I am pulling a 3500 lb trailer and I hit approx 50 mph the transmission goes into overdrive. When it does this I feel a shudder sensation. Is this normal? It is almost like it is trying to push the truck too fast forward and can't do it. I am perplexed.



It doesn't shudder when I am not pulling anything.



Any insight would be much appreciated.



Thanks!

Mark

 

[David Muench]

Is it when it goes into overdrive, or when it locks up the torque converter in 4th? If it's the latter, and there's a large RPM drop too, it's probably just the transmission dragging the transmission down and it vibrates a bit. My 47RE does it too, even empty if it drags down far enough.

 

[MRay0324]

How do I tell difference?

David,



I am not sure of the answer to your question. I think it is when it locks up the torque converter but I don't know how to distinguish between locking up the torque converter and going into overdrive? How do I tell the difference?



Thanks!

Mark

 

[David Muench]

I can't be sure on a 48RE, I've never driven one. But on my 47RE, the sequence is normally 1-2-3-4-4locked. The 3-4 shift usually doesn't result in a large rpm drop, but once the converter locks up there is a large rpm drop at low to medium throttle, since the engine is getting pulled down.

 

[MRay0324]

What Dodge Diesel Mechanic Said!

David,



I took it to the Dodge dealer this morning and the diesel tech told me that I shouldn't't be towing in OD. He said that when I approach the 50 mph shift point I should shut off OD and only engage OD when on the highway. He said the shudder is caused by the vehicle trying to go into OD when pulling a load. He checked my transmission and everything was fine, no codes, no problem with fluid, etc.



This perplexes me as I am only towing 3500 lbs and by not using OD you are taking the diesel engine out of its peak torque range of 1400 rpm up into the 2000 rpm range. If this was a gas engine I would understand the argument - as higher rpms is better for a gas machine. I could understand the shudder if I was pulling 20000 lbs, but not 3500. My brother has a 94 with a 47RE and he never ever takes it out of overdrive and has never had a problem when he pulls 7000 lbs.



Do you leave it in overdrive or how to you drive with a load behind personally?



Any one else with viewpoints on their driving habits regarding OD would be appreciated too!



Thanks!

Mark

 

[David Muench]

You can certainly tow in overdrive, but you do have to be aware that the RPM's will drop a lot between 4th and 4-locked if you're not on the throttle pretty good.



I'll be honest, I haven't towed anything yet. Zilch. I'm sure I will be in a month or so when the weather is good and my property dries out though.



If I am at a stop and accellerate away towards a nearby steep hill, I usually preemptively hit the OD lockout button so it doesn't go into OD till I want to at a higher speed. I like the feel of the 1-2-3-3locked-push OD button at a higher speed-4-4locked shifts anyway, the truck feels much stronger. I'd do the same towing. The truck just is choosing to go into OD sooner than it should. It's exaggerated in my case because I have 3. 73's and 35" tires. I love that combination, but the transmission goes into overdrive at as low as 1100-1200 rpm with light throttle.



I would just add that if you're towing, I'd try to keep it closer to 1800-2000 rpms anyway to help prevent lugging. The engine will be happier, and the driveline will be too.

 

[Steve M]

With my '01. 5, I had to let off the throttle to get it to shift into O/D or stay in the throttle until up to 65mph (3. 55 ratio) and then it would shift to O/D on it's own. I liked it that way but enough people whined about it so a TSB was born to fix our automatic "tow mode".

My '03 is overly anxious to get into O/D. I'm starting to figure out the new program though. While towing or even running empty, if I'm accelerating and I want it to stay out of O/D a little longer, I can give it a brief heavy throttle and it'll hold out until I let off the throttle. This only works if I give it the throttle before 40mph when it locks up the TC. If I wait too long it'll lock up and I can hear the turbo's bypass diaphram phrapppp as the TC locks up.

I wouldn't mind having the old program back. Even with light acceleration, it wouldn't shift to O/D until I let off the throttle.

Our new trucks are supposed to "learn" our driving habits and shifts accordingly. Mine has a short attention span.

If all else fails, there's the O/D button to fiddle with.

 

[CPritchett]

My ho with 48re pulls my 7,000# tt fine in overdrive, shifts fine pulling too. I took it back to the dealer for them to check a vibration when it shifted at 48 mph and locked up in overdrive, it felt like an old stick shift with a tailpipe vibration. They found a tie on the transmission dip stick tying it to the heater hoses was not tight so they tightened it and that helped some, but they told me with the power of the cummins and straight through lockup it was pretty well like a stick shift and that drone or light vibration from 48 to about 65 was normal. It stops at about 65 and is fine.

 

[RobG]

It will be interesting to wait about a year to see how many people with 48REs who tow large loads regularly start having transmission problems.



My old 47RE in my '96 died a horrible death, despite a BD converter and valvebody when I went to Colorado and back (5000 miles round trip -- lots of in between driving) with my camper and car on an open trailer (roughly 18k gcwr). That's how I ended up with a 6-speed and can't see getting anything but a stick in the future, at least until DC decides to put a real transmission in the trucks, like an Allison or somesuch.



I hope the 48RE proves me wrong... I'd love to be able to go back to an automatic, but I just doubt it will happen anytime soon. The more I look at the GMs and Fords, the less I want one. Cummins all the way.



Rob

 

[CATCRACKER]

all i can say this is the first negative post i have read about the 48re. you must know how to tow w/ an auto transmission, driver error can tear one up. run the rpms up that how you tow! towing tip:when towing turn od off, slowly smash the go pedal just fast enough to keep it from shifting to about 2600 rpms then let it shift. once you have reached cruising speed (65mph +) hit the od button again let it eat.



doing this alows the motor and transmission to share equally in the work. Thats where you want to be. This will help keep your transmission temps down and extend the TC's life.



of course this is my opinion.

 

[Prairie Dog]

Your Dodge mechanic is wrong. Dodge's official position is that it's fine to tow in O. D.

His comment could be true of some of their gassers but not the CTD.