68RFE 6-5-6 Gear Hunt

[jdross440]

After changing the gearing in my 2007.5 from 3.73 to 4.10's the transmission sometimes will shift from 6 to 5 and back again 2 times or more if the throttle is pushed even in the least (like going up a slight grade to maintain speed) or when speeding back up on the freeway after slowing some for traffic in your lane. Example: driving 50 mph and start up a slight hill. Or going 70 on freeway and slowing to 60-65 then pulling out to go around and speed back up to 70 (with or without cruise) it does this. Never did it before changing the gears. Also never did it when pulling my 5th wheel trailer. Do I need to take it to a transmission shop and have them run the "quick learn" on it?

 

[jdross440]

Drove it tonight and had more hills locally on a main highway (60 mph speed limit). It seems to be getting worse. I hope it's not something major in the transmission as this truck is starting to be a money pit this year with only 165K miles. First all driveshaft u-joints, then ECM-dealer charged $3850 for it. Ball joints and front axle u-joints are now needing replaced. Ball joints, axle u-joints and tie rods were replaced at 97K miles with MOOG parts and greased at every oil change. 2 months ago we had fluid and filters changed as at that time we were towing our 5th wheel the temp ran around 165 all the way until we got off the interstate and apparently when we got into traffic it went into limp mode and started heating up. Took me awhile to figure out what was going on as I finally tried to manually downshift and it was in 4th and wouldn't go any lower. By the time I could pull off out of traffic temp hit 245. As soon as I stopped I turned the key off and restarted truck and it would go into all the gears but had already got hot. Took it to a transmission shop the next day and they couldn't duplicate it but said the oil was burned. He took the pan off and said there was nothing in the pan-clean.Had code for overtemp. He did pull the factory cooler and checked it and said it was mostly stopped up-he put 100 psi in one end and almost nothing out other. Ended up buying a new factory cooler and also an aftermarket one put in line. No more problems until now. And with the cost of the gearing change then this we are about fed up.

 

[transe]

Did they tell you what the code was when it went into limp-in mode?
When cruising in 6th gear, if you tap the (-) switch on the shift lever once, does it show "5" or "6" in the dash display? (It should show "6").
Now tap it back to "D". Then, when it downshifts 6-5, tap the (-) switch again (once). This time, do you get "5", or still "6"? If you get "5", that confirms that the trans is downshifting. If you get "6", then the trans is not downshifting, and in that case I suspect your Torque Converter Clutch (TCC) is unlocking.

 

[jdross440]

When cruising it does show 6. When it downshifts it usually doesn't stay long enough to check, it goes down and up within 1-2 seconds and may do it up to 4 times (as I usually let off throttle by then). I have manually shifted to 5 and the rpm is the same as when it does it. I will try again later today as it is in front end shop today for the ball joints, axle u-joints. But it is possible the converter is unlocking and relocking. On the paperwork from the trans shop all it says is "trans overheated causing trans temp and OD pressure switch rationality codes". I have put about 2K miles on it since the trans shop.

 

[jdross440]

Added note: We have only towed the 5th wheel about 600 miles total. 300 to bring it home and then 300 round-trip to go camping. Before that we had a 33 ft bumper pull that weighed about 9500# loaded. It was pulled maybe 1000 miles. Other than that the truck has been used as a family driver.

 

[jdross440]

I tested it today on the way home from getting the ball joints, etc installed. It is staying in 6th and just the TC is unlocking and locking. As it relocks, the rpm comes down but not rapidly. It sounds like it is slipping a little as it re-locks.

 

[transe]

OK, then next step would be to have a tech with a scan tool ride with you to see what's going on. If the TCC is unlocking and relocking, you need to see if the TCC Status (on the scan tool) is changing accordingly. If the TCC Status is staying at Full Lock (Full EMCC) but the TCC is actually unlocking and relocking, then you probably have a bad converter (and I would expect it to set a P0740 "TCC Out of Range" fault). On the other hand, if the TCC Status is changing from Full EMCC to Partial EMCC or Open (Unlocked), then the trans / converter is simply doing what the TCM is commanding it to do. Since you apparently don't have a P0740 fault, this is what I suspect you'll find. If so, then I would check the throttle signal to see if you're getting a flaky throttle position reading. That might cause the TCM to fluctuate between different TCC states.

 

[jdross440]

Could there be something in the Smarty software that could cause this? It started about 2 weeks after re-installing it with the latest delete software? When the ECM died I reinstalled all the deleted items as the local dealer was having heartburn with the deletes.
Another thing I have noticed lately is when I put it in gear (forward or reverse) I am getting a vibration that wasn't there before. Almost feels like the engine is missing on one cylinder some. The rpm goes down a little, as I would expect with it going into gear.
Now to find a dealer that I trust. The local dealer I don't like. There is one 40 miles away I have had good luck with. I wonder if any of the transmission shops would have the scan tool to check this.

 

[transe]

I have no idea what your Smarty affects, but you could try going back to stock software and see if that "fixes" it.

 

[jdross440]

It is not supposed to affect anything except the engine parameters (turns off deleted items so they don't throw codes and changes fueling and timing for power increases). Setting 1 is a 30 hp increase (which is the lowest setting). When I had it on the truck before the new ecm, there was no transmission affects.
Do you know if only dealers have the software or do some transmission shops have it. I would think anyone that rebuilds these transmissions would have the software to troubleshoot. I will call some today.
I have to take the truck to the 4 wheel drive shop today for a severe vibration they are trying to find in the front axle-showed up after they put new gears in it.

 

[transe]

Trans shops should have scan tools to monitor the trans inputs and operational states.

 

[sag2]

Not sure if the sales code for 4.10 gears might need to be added to the truck and 3.73 removed. Having never done a gear swap I don't know if it has the same effect as it does on the passenger cars and Jeeps when the vehicle configuration is goofed up.

 

[Bob4x4]

I have discussed the re-gear/recongigure with our fleet tech advisor,he called his engineer and was advised against doing gear swaps on 4th gens as they have had less than consistant results and had to go so far as put all back to stock to get rid of some symptoms on some

 

[jdross440]

This is a 3rd gen. This problem didn't start until after I had put abut 1000 miles on the new gears. It may have to go back to original gears anyway as the 4 wheel drive shop is having a hard time figuring out why changing gears in the front caused a severe vibration at 55 and up. They have never had that happen according to them. They sent the driveshaft out twice for balance. You take the driveshaft out and the vibration doesn't show up. I have a different post on this matter.

 

[jdross440]

Before we did the gear swap we looked for a used mega cab dually or crew cab with 4.10 gears. None to be had as all had 3.73 or even worse 3.42. Why build a dually with 3.42 as they are intended for towing.

 

[Cummins12V98]

"Why build a dually with 3.42 as they are intended for towing."

With Aisin they are a GREAT gear set!!! Combined to around 28K I would go 3.42's anyday with the Aisin's lower starting gears. Tow in 5th same as 6th with 4.10.s and have the best fuel economy running solo.

 

[jdross440]

Actually with the 4.10's on the 2 300 mile each way trips I got almost 2 mpg better than with the 3.73. All the trucks we have looked at didn't have the Aisin transmission's.

 

[jdross440]

I drove it about 30 miles yesterday from 4wd shop to my home. It only did it once just before I got off freeway as it was relatively flat even though I did have to slow and speed up several times. However after I got off freeway and was going down 2 lane it would do it going up a grade. I went by transmission shop and talked to them. After I told him about the overheating episode he things maybe the torque converter is going out. He didn't have time to put his test equipment on it so have to take it back Monday for him to check it out. His equipment will also graph each gear and lockup to see what is happening. He rebuilds several of these (he has 3 in his shop now). He said they are good trannys. He said the weak links are the torque converter and reverse pall. When he changes torque converters he puts in HD billet TC's.He also said he has a friend with a 2009 that tows dozers on a 15K pound trailer and has a tuner turned way up and has no problems with his.
I called the dealer that I trust (and have had work done) that has a Certified trans tech that only works on trannys most of the time. He said changing gears won't require a computer update. He said it gets it's info off the rear end.

 

[jdross440]

The trans shop finally got to check my truck out Thursday (the holiday put them way behind as they were only open 2 days that week). He said the torque converter was gone as the lockup was slipping badly and kicking out of lockup. He also said there was a code for low line pressure which he said could be from an internal cause or a wiring issue. He said usually it is from an internal issue but has had them with a wiring problem. He is going to tear it down and rebuild it with all the updates and heavy duty parts and a billet torque converter. Anything else that is worn (valve body, etc) will be replaced too.

 

[jdross440]

Got the truck back from shop late Thursday. The guy said the forward clutches were totally melted/welded together. He didn't see how it was even moving but he had driven it of course to diagnose it and was really surprised how well it shifted other than not locking up. He put in a triple disk lower stall HD converter, at my request. We only live 3 miles from the shop city streets so didn't get to drive it at speed until late Friday afternoon. It now has a vibration/rumble when it shifts into 4th at about 35-40 mph that goes away as it up shifts (manual downshift to 4th it doesn't come back). Then at about 60 there is a vibration that gets a little worse up to 70 and stays steady up to about 80 then gets much worse. This wasn't there before overhaul. Today I jacked it up and put all 4 corners on jack stands and ran it in 2 wd and 4 wd. The vibration wasn't there as it shifted into 4th but as you neared 60 it started and by 70 it was pretty good. Worse in 4 wd. It looked like it was the right front tire so I rotated it to right rear inside. Made no difference. I even revved the engine in park up to 2500 rpm and no vibration. Tomorrow or Monday morning I am going to take front driveshaft loose at differential and rotate it 180 degrees and see if that makes a difference as I have heard on some of these Dodges it makes a difference if not put back in clocked the same (4 wd shop had balanced it with the pinion flange mounted on it before the overhaul). In 2wd there is a rumble going thru rear driveshaft (1 piece). I am also wondering if something in trans rebuild is causing this. He told me there was a vibration but he thought it was the front drive shaft. I told him it had all new u-joints in it and the balance shop said them and the centering ball were in good condition (and since it wasn't there before rebuild).