Auto transmission shudder while towing

[bedroc]

Deleted from turbo back to stock muffler along with EGR junk, did leave the cooler on but blocked. I am having trouble with the back 2 flange bolts, will get that later. Programmed with Smarty Jr ME on level 2. I do like the added power and quicker throttle responses. Ran this way for a couple weeks to make sure it was all good.

Went on vacation pulling our Jayco 32" bumper pull 7000# camper. Truck did great and fuel mileage was up a mpg or so. The only issue we had was this. While on cruise control running about 65 mph in the gentle rolling hills of Kansas pulling up hill just before the transmission would shift from 6th to 5th it would shudder. RPM's would slowly drop to 1100 before the shudder began. Truck was in tow/haul mod as well. The shudder will not go away unless I intervened ie:

1. step into the skinny pedal so to force downshifting

2. kick the cruise off

3. manually select 5th



On our way back home I changed the tune to level 1. The shudder was not as bad or so I thought, DW had other comments.



I talked to the folks over at Rollin Smoke and was told this happens because the cruise control is trying to maintain 6th gear. I thought since I was in tow haul mode it should know to downshift sooner to maintain rpm's in the power curve.



Of course I could run the hills with cruise off and avoid the issue altogether. My question is will pressure booster or ATS co-pilot cure my problem. Keep in mind I am not out to increase the trucks power level beyond what Smarty Jr can do.



Thanks

 

[Wiredawg]

For Smarty Programs (not sure if the same for Jr), you need to run only odd numbered levels... even numbered levels eliminates ECM timing... odd numbers keeps it. Check online and instructions that came with your programmer. I thought tow/haul would not allow to shift to 6th... It prevents 6th shift on the Aisins. Others can comment on the transmission end on the 68RFE.

Wiredawg

 

[RustyJC]

Tow/haul does NOT disable 6th gear on the 68RFE.

Although neither bombed nor deleted, my truck has never pulled down to 1100 RPM before a downshift when towing with the cruise control activated and tow/haul in use.

Rusty

 

[Wiredawg]

Rusty/All,

I believe I would drop it down to 5th then. I realize there's lots of diff between my 4500 C&C, but when we towed our 17K lb 5er out to Canada last year, I started with it in double overdrive. I had Smarty on level-5 (90HP) and it woud shudder on down shifts and upshifts going through grades. I changed to tow/haul, which changes shifts and omits 6th. I got better performance and mileage running 70mph at approx 2400 rpm than at 2100 rpm. Although different programming, I believe you will see similar imrovements.

Ron

 

[mpaulson]

I never allow the cruise control to have a shift, I can't stand the slow lock up after the shift to fifth. The clutch material trying to slow down all that HP while at full power and towing. The T/C will not last long doing that. If I forsee a shift coming up when I approach a climb, I cancel the cruise and control the power my self and if I need to down shift, then I paddle shift it and back off on the throttle till the T/C is locked up then get back on it. The slow lock up in fifth is very annoying since you loose more speed waiting for it to lock up. I can't stand the way the truck shifts while using cruise control, way to slow and/or harsh for me. The 1100 rpm's is odd and not normal and would be why you are getting the shudder. Since you are your own warrenty station now, manually control the truck while towing around hills and keep the rpms above 15-1600 minimum in my opinion.
If you are heavy and have the 3. 73 gears, run in 5th gear all the time. This is what I did before I did a gear switchout. This had me at 2300rpm at 70mph, not lugging, not screeming and not bogging down on medium hills so fast.

 

[bedroc]

Truck has just under 60k on it. Should have mentioned that I became my own warranty station on 14 Apr 12 when a tornado did just enough body damage for the insurance to total it, bought the truck back. Sure drives alot nicer with no payments

Even when rpm's were down to 1100 it did not feel/sound like the engine was lugging. I'll try running the hills next time in 5th gear.

Thanks for all the tips.

 

[AH64ID]

For Smarty Programs (not sure if the same for Jr), you need to run only odd numbered levels... even numbered levels eliminates ECM timing... odd numbers keeps it. Check online and instructions that came with your programmer. I thought tow/haul would not allow to shift to 6th... It prevents 6th shift on the Aisins. Others can comment on the transmission end on the 68RFE.

Wiredawg

All 3 levels of the JR have added timing, unless TM1 is selected.

 

[Matt_L]

Smarty is having troubles right now with surging/shuddering for both the JR and SR for the 4th Gen tuners. Unfortunately you will have to wait for them to release an update to stop the surging. At the rate they release updates these days, you might have to wait a while

 

[JDinNY]

With the increased torque from the Smarty, the trans line pressure isn't high enough at 1100 rpms to keep the converter clutches from slipping under acceleration. I do as another member selected and drop down a gear manually to prevent this. I found this out early on towing my skater, only 1600 lbs with cruise on in rolling upstate NY hills. The power would come on way too aggressive at low rpms. I did add a BD pressure lock, but really don't think they do much if anything at all. Keep your rpms up over 1500 and you should be ok.

 

[LNaugle]

I think this problem is why H&S has tc control upgrade... .

 

[bedroc]

I decided to try H&S Mini Maxx to see if different programming would make a difference. So to make is a true test, made the same trip as in the first post. Ran the same roads with same trailer.



On the way out MM was set to level 1. With cruise set @ 65mph the truck pulled the hills maintaining speed shifting smoothly up and down the hills. RPMs never dropped below 1500. No sign of the previous shudder what so ever. A few times I did use the paddle shifter to see if I could make the shudder happen as before, I could not.



On the way home I tried MM on level 2 for a short while to see if it made a difference in how the transmission shifted. It was still smooth even with the increased power level, but it felt a little 2 aggressive. I reverted back to level 1 after 50 miles so as to cause to much stress on the drive train.



Over all the truck sounds and runs smoother with MM than it did on Smarty Jr. I liked it so much I'm thinking of springing for the Overdrive tune.



We were about an hour from home and got EVIC message "Exhaust systems service required see dealer now" The message would display every 10 min along with a very annoying ding ding ding. There where no codes. The message went away on its own or at least it hasn't been back the last 2 days. I haven't added an external waste gate yet. Could that message be caused by high drive pressure with ECM thinking the EGR cooling is plugging up?

 

[cornstalk1]

Deleted from turbo back to stock muffler along with EGR junk, did leave the cooler on but blocked. I am having trouble with the back 2 flange bolts, will get that later. Programmed with Smarty Jr ME on level 2. I do like the added power and quicker throttle responses. Ran this way for a couple weeks to make sure it was all good.
Went on vacation pulling our Jayco 32" bumper pull 7000# camper. Truck did great and fuel mileage was up a mpg or so. The only issue we had was this. While on cruise control running about 65 mph in the gentle rolling hills of Kansas pulling up hill just before the transmission would shift from 6th to 5th it would shudder. RPM's would slowly drop to 1100 before the shudder began. Truck was in tow/haul mod as well. The shudder will not go away unless I intervened ie:

1. step into the skinny pedal so to force downshifting
2. kick the cruise off
3. manually select 5th

On our way back home I changed the tune to level 1. The shudder was not as bad or so I thought, DW had other comments.

I talked to the folks over at Rollin Smoke and was told this happens because the cruise control is trying to maintain 6th gear. I thought since I was in tow haul mode it should know to downshift sooner to maintain rpm's in the power curve.

Of course I could run the hills with cruise off and avoid the issue altogether. My question is will pressure booster or ATS co-pilot cure my problem. Keep in mind I am not out to increase the trucks power level beyond what Smarty Jr can do.

Thanks

I had the exact same problem with mine and I was also dealing with Rolling Smoke. This weekend I changed my tune to Standard on the Smarty Jr. and I didn't get any shudder while towing this time. I talked to a trans shop and they said the torque converters in these trans cant handle any extra torque and that is why I was getting a shudder.