Pickup for my son

[Jim Culp]

I bought a 2008 Dodge 2500 4x4 with a 170,000 at a auction a few days ago for my son it has the 6.7 diesel with an automatic trans. the truck drives around just fine when you first take off with everything cold it will shift all 6 gears however when it states to warm up the truck will down shift to 4th gear only. there is no check engine light on or codes in the system. I took the truck to my local repair shop and they could not find anything wrong with it and did not know why it was not shifting right. they told me to just drive it for a little while and see if something changes. That's not my way of doing thing if something is wrong you fix. any help would be appreciated

 

[AH64ID]

The trans will limit gears based on fluid temps. I would use a scanner and monitor temps to see if they are appropriate for the conditions.

 

[Topzide]

I would do full fluid changes. There info here to help with getting all fluid out of trans and change filters for starting point; https://www.genosgarage.com/tech_info
What is the color of the trans fluid? Does it have a very dark to black look on a white paper towel? Also does it have a burnt smell?
170K isn't that big of deal on these trucks. As @AH64ID has stated, pick up an infrared thermometer to check what temps are doing. Having a good starting point with maintenance will be a big help with life of the truck. Hopefully if wasn't to abused before you picked it up. There's plenty of help on TDR. Just post up questions.

 

[Jim Culp]

The fluid look new and does not have any burnt small to it. I had another person tell me that if someone changed the fluid and filter and refilled it with something other than ATF+4 then it could have problems like this. has anyone else ever heard of this before?

 

[Ozymandias]

Go with AH64s advice.

 

[Topzide]

The fluid look new and does not have any burnt small to it. I had another person tell me that if someone changed the fluid and filter and refilled it with something other than ATF+4 then it could have problems like this. has anyone else ever heard of this before?

Another good reason to get it all out since bought from an auction. Never know what and or why things were done before the auction!

 

[Jim Culp]

I pulled the pan and there was just a little bit of black on the magnet but the fluid did look a little bit dark when I could see more than what was on the dip stick.

 

[Ozymandias]

The fluid won't make it shift only to 4th gear. Nope.

 

[sag2]

Does it only shift 1-4, or does it start in 4th? Big difference between the two.

 

[Jim Culp]

it will shift 1-4 after it gets warm but before you drive it around 5 miles or so it will shift all 6 gears

 

[AH64ID]

it will shift 1-4 after it gets warm but before you drive it around 5 miles or so it will shift all 6 gears

You really need to see what the temp sensors are reporting….

 

[Topzide]

Could the pressure transducer have failed? Seems that may be an issue after reaching temp. Again, once back together, check temps with infrared thermometer. Need to rule out what you can and with that info, others will have a better idea of what is happening. Good luck!

 

[Jim Culp]

I had to order the filters so it will be Wednesday afternoon before I can get it back together to check the temps. The only way I would have to check the Temp is a Lasor temp gun is there a special spot I should get a the best reading using this kind of equipment.

 

[Topzide]

I would check the lines, trans cooler at both inlet and outlet and trans pan. Make a chart to fill it in at different times and maybe even the miles driven. That way it could be looked at to give comparison of what is going on. The laser unit will help with get an accurate result! Looking forward to what you find.

 

[AH64ID]

I had to order the filters so it will be Wednesday afternoon before I can get it back together to check the temps. The only way I would have to check the Temp is a Lasor temp gun is there a special spot I should get a the best reading using this kind of equipment.

You need to get a scanner and see what the computer is seeing. The computer will lock out OD if the fluid is too hot or too cold, so that’s the data you need.

It’s very possible you have a temp transducer failing, which is something a laser gun won’t indicate. The laser gun can help validate temp signals, but based on what you have described it’s not the primary measurement you need.

 

[Ozymandias]

You need AlfaOBD for this, not a generic OTC Scanner.


Edit. I wonder how factory that truck still is.. to many vehicles out there by now that have been molested and tampered with.

 

[cerberusiam]

Downshift to 4th gear on a 68 is limp mode, as the fluid warms it gets thinner and then the problems start with CV indexes and it goes into protect mode. Those transmissions had so many problems it is not unusual to see that happen. IIRC, those year trucks had a separate TCM that it take special software, read that DODGE only, to read the codes. It has codes somewhere to tell you what is wrong. If you see electrical faults like high and low readings it is probably the solenoid pack, if the codes fill indexes and gear mismatches it is hardware related.

 

[Jim Culp]

I took it to a trans shop and found out that the over drive clutch pack was all but out. so I just had them do a complete rebuild on it.
thank you to everyone that give me all the help with this project.