Hey guys,

Back with another question. Figured I'd ask it over here since the SD forums have not been much help as of late.

Here is the problem, 2002 CCLB Dually 7.3 SD with a 4r100, recently developed a shift issue between 2nd and third. No stored shift codes currently. Friends truck.

Its pretty hard to explain, but when cruising around 35-40mph on the country roads the truck will shift from 3rd to second, and back to third a few times rather quickly (within 8 seconds). Its not load induced, or if the accelerator is pressed or depressed. It definitely is almost like a slip in the trans or an issue of it not knowing what gear to be in. The common answer would be press the pedal to stay in the downshift, pick up speed and then let off...its not one of those situations. Its worse when cold too.


Here is the odd part, press the OD button to off, it goes away. Accelerate hard through the gears it will not happen. Not being a truck I drive everyday I could notice the issue as well. He said it just had started recently.

Is this a torque converter lockup issue? Line pressure? Internal leak that is preventing full pressure at this odd speed? Trans diode? Solenoid pack? I am not a transmission guy by any means. I put them in and take them out and try to understand as much as I can down at the trans shop when we chat on the workbench. I thought I'd bring it up to you guys.

He bought the truck around 200k it has 310 on it now. I do not imagine this was an original trans based upon the Banks package on it and evidence it was a hard towing truck.

Anyways I was wondering what all of your thoughts are? Mark Kovalski want to chime in? Before we take it to a trans shop and they say pull it, it would be nice to hear a few other opinions.

We use a very reputable trans shop, they are pretty incredible in turn around time and quality. If we can't figure it out, off it goes to them.

 

It could be any of those, except the trans diode. I think you're referring to the Mechanical Diode, and that was only in the first half of the 2001 model year. No 2002 had one.

The only way to find out what it is would be to use a scan tool that can look at live data. Is the PCM commanding the shift? Is the input from one or more sensors out of whack? Without this data all anyone can do is guess.

 

Thanks Mark and understood. Thanks for the correction on the 2001/2002 year as well. I did not know that.

Autoenginuity is not going to cut it for live data to the trans. Looks like it may be going to the shop then... see if they can give us an Idea of what may be going on....

 

I know this may sound elementry, but what's the fluid like in it? I just solved some issues I was having with my trans by just by changing fluid. It was doing weird shifting and some slipping as well. It only had 12k on the fluid but it was very dark. And smelled burned. Since the change its gone back to normal. Im just buying time I know, but any more I can get out of it is better than not.

 

Agreed. Fluid is not bad. been changed twice in about 80k. He is going to take it in to the trans shop and leave it with them and see what they diagnose.

Sometimes it works, but I know a lot of dudes who had slipping issues and wasted 300$ on a synthetic flush.... right before rebuilding it after it blew up :-)

 

Yeah this is defiantly a stop gap measure. I'm nervous being it trashed the fluid in only 12k miles. Its never gotten hot on the gauge, but there's defiantly signs its not new. I'm just trying to prolong it as best I can. Lol.

Hopefully the shop finds Somthing that doesn't involve spending thousands of dollars.

 

subscibe...

 

There hasn't been a post in this thread in five years. Don't expect many more.