Transmission shifting issues when climbing mountain passes

FarmerMT · 05-29-2011, 10:56 PM

My tow vehicle is a 06 Dodge Ram 2500 Hemi. I ran into some major issues towing my camper up a large mountain pass. The vehicle kept up shifting and downshifting (automatic tranny in tow/haul mode) for several miles around 40 to 50 mph. It got so bad that I pulled behind a semi going 30 and just held that speed in 2nd gear until I crested the hill. The rest of the trip was fine. There is no problems climbing small hills. I have a Bully dog tuner and can adjust my shift points. Has anyone else done this? Do you know what RPM's you set your shift points at?

**KyDan** · 05-30-2011, 06:39 AM

I don't have your truck so this might not help but when I'm on long haul mountain
roads I drive in a lower gear.
I always tow in 3 rather than OD. I've found that tow haul in my truck makes tranny shift
down too soon and it stays in the lower gears too long for my taste.
I don't use tow haul much.
If the hill is really long and steep it's not unusual for me to run in 2nd.
I mean my shift lever is in 2.
I can run at 45 mph and around 3500 rpm and I can do that all day if necessary
without seeing the temp gauge move up any.

What RPM are you turning in 2nd at say 40/45 mph?

crocus · 05-30-2011, 07:42 AM

If I get into the situation where my tranny doesn't know what gear it wants to run in, I manually downshift. Saves those tranny clutches!

Glenn5995 · 05-30-2011, 07:53 AM

Which gears was it shifting between? It sounds like you were able to hold it in 2nd gear which is not unusual for pulling a grade. I tow for miles in 2nd gear on mountain grades.

If it was shifting between 3rd and 4th, then you need to lock out the OD gears. 4th and 5th gears are both OD gears on the 545RFE. You say you were in Tow/Haul mode, that changes the shift parameters and locks out 5th gear, but still permits 4th gear. If you push the button on the end of the transmission gear selector once, it goes into "Tow/Haul Mode". Push the button a second time and the transmission will go into "OD Off" mode. This retains the Tow/Haul shift parameters and locks out 4th and 5th gear ODs, so the transmission will not shift beyond 3rd (Drive). You may then use the transmission selector lever to hold it in 2nd or 1st as needed.

SaskCampers · 05-30-2011, 08:26 AM

Quote:

Originally Posted by Glenn5995

Which gears was it shifting between? It sounds like you were able to hold it in 2nd gear which is not unusual for pulling a grade. I tow for miles in 2nd gear on mountain grades.

If it was shifting between 3rd and 4th, then you need to lock out the OD gears. 4th and 5th gears are both OD gears on the 545RFE. You say you were in Tow/Haul mode, that changes the shift parameters and locks out 5th gear, but still permits 4th gear. If you push the button on the end of the transmission gear selector once, it goes into "Tow/Haul Mode". Push the button a second time and the transmission will go into "OD Off" mode. This retains the Tow/Haul shift parameters and locks out 4th and 5th gear ODs, so the transmission will not shift beyond 3rd (Drive). You may then use the transmission selector lever to hold it in 2nd or 1st as needed.

Ditto,

I was however unsure what year they made the change that you had OD lockout as our 04 only had T/H and normal but our 08 has T/H and OD Off.

Glenn5995 · 05-30-2011, 08:30 AM

2006 was the change.

M109Rrider · 05-30-2011, 12:04 PM

Yep, gotta love the 545re. The gear ratio's are all wrong for towing. 99% of the trucks on the road have never pulled a trailer or carried a heavy load so manufactures build them for fuel economy vice towing/hauling. Hemi's love RPM, that's where they make all their torque so don't be scared to let it rip. Had a '04 1500 HEMI with 3.92's before the cummins. I ended up putting 4.56's in which made a day and night difference when towing. I could only lock out 5th but the new gears stopped most of the hunting.

backin15 · 05-30-2011, 12:22 PM

I have a '04 with the 3.73's and also can only lock out 5th. I have been looking at switching to 4.56's to keep it from hunting between 3rd and 4th on the highway. I wish there was a way to retrofit to the post '06 setup so I could lock it into 3rd. I don't suppose your Bully Dog tuner would do this?
I only did a steep pull at altitude once and could not get it to downshift. I had the foot to the floor and the rpm's werre so low the speed was dropping. I made it to the crest before I had to manually drop it into first though but I have always wondered why it didn't automatically downshift.

flyrotor · 05-30-2011, 02:12 PM

Shifting like you describe is tough on the trucks, my suggestion is just let off the throttle to a comfortable RPM in the lower gear just like you stated you did, let the engine work but slow it down so the transmission doesn't take the abuse

Glenn5995 · 05-30-2011, 02:42 PM

Quote:

Originally Posted by backin15

....I only did a steep pull at altitude once and could not get it to downshift. I had the foot to the floor and the rpm's werre so low the speed was dropping. I made it to the crest before I had to manually drop it into first though but I have always wondered why it didn't automatically downshift.

Like M109Rider said "gotta love the 545RFE". Fortunately Power Wagons have 4.56s gears OEM, so that helps quite a bit and with mine being a 2006, I can hold it in any gear, which is a huge benefit. The 2005s and earlier had no way to keep it from shifting between 3rd and 4th.

The problem you had was because of the wide spacing between 2nd Prime and 1st. The 545RFE is marketed as a 5-speed because it functions in that manner, but it actually has 6 forward gears. Because of the wide spacing between gear ratios there is an alternate 2nd gear for downshifts which is higher than the 2nd gear used for upshifts. As a result when it downshifts from third, it is a gear ratio that is closer to 3rd and a LOOOOOONG way from 1st. The result is the transmission can't downshift into first until the speed has dropped enough to permit the downshift without over revving the engine. The result is exactly as you described, you keep pushing on the gas pedal, but the speed and RPMs keep dropping until they are low enough to allow a downshift.

I have learned to cheat it if I'm in an area I am familiar with and can anticipate the grade. Before the grade, I will slow enough to manually pull it into first gear and then put the selector into 2nd and allow it to UPSHIFT into 2nd (the lower 2nd gear) and stay there. By not allowing it into 3rd, it won't DOWNSHIFT into 2nd prime. By doing this grades that otherwise would have forced me to slow and drop into 1st, I am able to maintain a higher speed and stay in 2nd.

SaskCampers · 05-30-2011, 02:49 PM

Quote:

Originally Posted by Glenn5995

Like M109Rider said "gotta love the 545RFE". Fortunately Power Wagons have 4.56s gears OEM, so that helps quite a bit and with mine being a 2006, I can hold it in any gear, which is a huge benefit. The 2005s and earlier had no way to keep it from shifting between 3rd and 4th.

The problem you had was because of the wide spacing between 2nd Prime and 1st. The 545RFE is marketed as a 5-speed because it functions in that manner, but it actually has 6 forward gears. Because of the wide spacing between gear ratios there is an alternate 2nd gear for downshifts which is higher than the 2nd gear used for upshifts. As a result when it downshifts from third, it is a gear ratio that is closer to 3rd and a LOOOOOONG way from 1st. The result is the transmission can't downshift into first until the speed has dropped enough to permit the downshift without over revving the engine. The result is exactly as you described, you keep pushing on the gas pedal, but the speed and RPMs keep dropping until they are low enough to allow a downshift.

I have learned to cheat it if I'm in an area I am familiar with and can anticipate the grade. Before the grade, I will slow enough to manually pull it into first gear and then put the selector into 2nd and allow it to UPSHIFT into 2nd (the lower 2nd gear) and stay there. By not allowing it into 3rd, it won't DOWNSHIFT into 2nd prime. By doing this grades that otherwise would have forced me to slow and drop into 1st, I am able to maintain a higher speed and stay in 2nd.

Great idea Glenn.

M109Rrider · 05-30-2011, 03:06 PM

Right on Glenn. 2nd prime is also a weak link in the 545. It uses a weaker band (the reverse band I believe) with less holding power and is prone to burning up, particularly in modified trucks.

sherdep · 05-30-2011, 04:19 PM

I have the Superchips programmer with the shift point options but I am running 35" tires with 3.92 gears.
Mine doesnt hunt gears as bad but it lags before it finally down shifts.

you will most lilkely need to change your tune for the shift points.

When I was a Beta tester we had a Xcel spread sheet with a graph that allowed you to see your shift points but I never got the hang of it cause it was a pita to keep changing and tuning and changing and tuning

I know on Dodgetalk.com there was a big discussion on the shift points when superchips came out with the programming for it - as a matter of fact my truck was a beta tester for the shift points for a 3rd Gen Ram.

**KyDan** · 05-31-2011, 06:36 AM

Dang, kinda makes me long for the old days when trucks were
manual tranny and we were all gear jammers on the hills.
(I actually drove milk/dairy trucks that had manual trannys that did
not have synchronizers so you had to double clutch to change gears.
They had 2 speed rear ends too.)

FarmerMT · 06-03-2011, 08:29 AM

Thanks for all of the information. My truck does have both the tow/haul and O/D shut off options. I did not try the O/D off. My Bully Dog does allow me to change shift points. I need to research some towing shift points for it and set what RPM it will shift at for each gear. I will only travel this type of pass twice a year (thank goodness) I had no problems at all on long steep grades just this one pass that went very steep over a short distance.

08flagvlite · 06-03-2011, 10:26 AM

Not to change the subject, but on the 545 RFE, have any of you heard of using DextronIII, and then using an "additive" to convert it to ATF+4? This is exactly what AAMCO is doing because the ATF+4 is a fully synthetic fluid, and about 2.50 a bottle more than Dex 3. That way they keep down their cost of a trans fluid and filter service. Makes me wonder if it is okay to do that! The dealer of course says to use ATF+4, as stated on the stick, spec.9602.
My son's 95 Dodge Ram 1500 5.2 has a 46 RH tranny that we just yesterday rebuilt and re-installed in his truck. t says on the stick Chrysler spec.7176 fluid, OR Dextron 2.
Why are Dodge trannys so confusing!! I put ATF+4 spec 7176 on the bottle from Oreilly's at 5.69 per bottle synthetic, just to be safe. 60.00 worth of fluid by itself! Works good though. Randy

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