My 2009 Liberty has the factory installed tow package which includes a towing mode feature. The tow mode keeps the transmission from going into overdrive. My hauling consists of an occasional trip with dad's 2700lb bass boat or 4000lb of firewood. When hauling on flat sections of the interstate, I usually turn off tow mode and let the transmission go into overdrive, but will upshift (turn tow mode on) when approaching a hill. In tow mode, I am around 3000rpm at 60mph. Am I hurting the transmission by letting it get into overdrive? Are rpms in that range over a long period of time damaging to the engine?
Jeep Liberty Tow Mode
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Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
Should be fine on flat surfaces
I think for flat surfaces you should be fine. Does your Jeep have a transmission cooler? As long as you keep the fluid in good condition I wouldn't worry about it if you don't tow very often.
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I think this is the important factor. Regularly locking and unlocking the TC is bad for everything.
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I think this is the important factor. Regularly locking and unlocking the TC is bad for everything.
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Originally Posted By: outoforder
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. If it is going in and out of overdrive when you switch out of tow mode, that will cause excessive heat and wear on the transmission. In that case, I would just leave it in tow mode when towing. The higher RPMs won't hurt the engine one bit.
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. If it is going in and out of overdrive when you switch out of tow mode, that will cause excessive heat and wear on the transmission. In that case, I would just leave it in tow mode when towing. The higher RPMs won't hurt the engine one bit.
Originally Posted By: outoforder
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. First it shifts to O/D with the convertor unlocked, then locks the convertor. If you see it repeatedly locking and unlocking, that's bad and you should just lock out O/D. Sustained higher RPM with the convertor locked is better than low RPM but constantly locking/unlocking.
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. First it shifts to O/D with the convertor unlocked, then locks the convertor. If you see it repeatedly locking and unlocking, that's bad and you should just lock out O/D. Sustained higher RPM with the convertor locked is better than low RPM but constantly locking/unlocking.
Originally Posted By: 440Magnum
Originally Posted By: outoforder
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. First it shifts to O/D with the convertor unlocked, then locks the convertor. If you see it repeatedly locking and unlocking, that's bad and you should just lock out O/D. Sustained higher RPM with the convertor locked is better than low RPM but constantly locking/unlocking.
Exactly. If you are cruising at a constant speed the rpm's should stay constant. If the converter is locking/unlocking you will see it jump and settle a couple hundred rpm every time it happens even though your speed stays the same.
Originally Posted By: outoforder
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. First it shifts to O/D with the convertor unlocked, then locks the convertor. If you see it repeatedly locking and unlocking, that's bad and you should just lock out O/D. Sustained higher RPM with the convertor locked is better than low RPM but constantly locking/unlocking.
Exactly. If you are cruising at a constant speed the rpm's should stay constant. If the converter is locking/unlocking you will see it jump and settle a couple hundred rpm every time it happens even though your speed stays the same.
Originally Posted By: jeepman3071
I think for flat surfaces you should be fine. Does your Jeep have a transmission cooler? As long as you keep the fluid in good condition I wouldn't worry about it if you don't tow very often.
Yes, it has a transmission cooler.
I think for flat surfaces you should be fine. Does your Jeep have a transmission cooler? As long as you keep the fluid in good condition I wouldn't worry about it if you don't tow very often.
Yes, it has a transmission cooler.
Originally Posted By: bepperb
Originally Posted By: 440Magnum
Originally Posted By: outoforder
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. First it shifts to O/D with the convertor unlocked, then locks the convertor. If you see it repeatedly locking and unlocking, that's bad and you should just lock out O/D. Sustained higher RPM with the convertor locked is better than low RPM but constantly locking/unlocking.
Exactly. If you are cruising at a constant speed the rpm's should stay constant. If the converter is locking/unlocking you will see it jump and settle a couple hundred rpm every time it happens even though your speed stays the same.
Ok, I understand what y'all are saying. When traveling flat at cruise control, the rpms stay constant. But if I start up the slightest incline or apply a litter pressure to the gas pedal, the torque converter unlocks and the rpms go up by a few hundred.
Originally Posted By: 440Magnum
Originally Posted By: outoforder
Originally Posted By: bepperb
Can you tell from the tach if the torque converter is locking/unlocking when you are in overdrive?
I notice that after shifting into overdrive, the rpms drop. Then after a second or two, the tach will drop another few hundred rpms. Is this what you are referring to?
Yes. First it shifts to O/D with the convertor unlocked, then locks the convertor. If you see it repeatedly locking and unlocking, that's bad and you should just lock out O/D. Sustained higher RPM with the convertor locked is better than low RPM but constantly locking/unlocking.
Exactly. If you are cruising at a constant speed the rpm's should stay constant. If the converter is locking/unlocking you will see it jump and settle a couple hundred rpm every time it happens even though your speed stays the same.
Ok, I understand what y'all are saying. When traveling flat at cruise control, the rpms stay constant. But if I start up the slightest incline or apply a litter pressure to the gas pedal, the torque converter unlocks and the rpms go up by a few hundred.
I'd use the tow haul mode. It isn't worth it taking a chance. What you're describing is telling me you're better off not using OD for towing.
what does the owners manual say about towing? plus 4k sounds like a lot for a libby.whats it rated to tow?
Originally Posted By: Chris142
what does the owners manual say about towing? plus 4k sounds like a lot for a libby.whats it rated to tow?
Its tow rating is 5,000 lbs. This is from the 2008 Liberty owners manual.
"Towing Tips-Automatic Transmission" The "D" range can be selected when towing. However if frequent shifting occurs while in this range you will want to activate the TOW/HAUL feature. Refer to "Automatic Transmission" in this section for additional information.
NOTE: Using the TOW/HAUL feature while operating the vehicle under heavy operating conditions will improve performance and extend transmission life by reducing excessive shifting and heat build up. This action also provides better engine braking. If you REGULARLY tow a trailer for more than 45 minutes of continuous operation then change the automatic transmission fluid and filter according to the interval specified for "police, taxi, fleet or frequent trailer towing" in the "Maintenance Schedule" in this manual.
HTH
what does the owners manual say about towing? plus 4k sounds like a lot for a libby.whats it rated to tow?
Its tow rating is 5,000 lbs. This is from the 2008 Liberty owners manual.
"Towing Tips-Automatic Transmission" The "D" range can be selected when towing. However if frequent shifting occurs while in this range you will want to activate the TOW/HAUL feature. Refer to "Automatic Transmission" in this section for additional information.
NOTE: Using the TOW/HAUL feature while operating the vehicle under heavy operating conditions will improve performance and extend transmission life by reducing excessive shifting and heat build up. This action also provides better engine braking. If you REGULARLY tow a trailer for more than 45 minutes of continuous operation then change the automatic transmission fluid and filter according to the interval specified for "police, taxi, fleet or frequent trailer towing" in the "Maintenance Schedule" in this manual.
HTH
Originally Posted By: eljefino
D (D3) with TCC lockup in Tow/ Haul mode sounds like the winning combo. And keep it under a mile a minute...
Yes, 60 mph seems to be the sweet spot for interstate driving. Just got back from towing about 1300 lbs for 60 miles. There was frequent shifting when the transmission was allowed to go into overdrive. In tow/haul mode at 60 mph, the tach runs about 2700 rpms and the vehicle tackled all hills/inclines without shifting. Figure the extra gas used is cheap insurance vs shortening the life of a transmission.
D (D3) with TCC lockup in Tow/ Haul mode sounds like the winning combo. And keep it under a mile a minute...
Yes, 60 mph seems to be the sweet spot for interstate driving. Just got back from towing about 1300 lbs for 60 miles. There was frequent shifting when the transmission was allowed to go into overdrive. In tow/haul mode at 60 mph, the tach runs about 2700 rpms and the vehicle tackled all hills/inclines without shifting. Figure the extra gas used is cheap insurance vs shortening the life of a transmission.
I would never tow a sizeable load in OD. Even if the TC stays locked.
There is information missing in common "car lore" about why we are supposed you avoid OD. It's not Just the TC and fluid heat and clutch wear from that shifting. It has to do with the OD gearing itself.
I take the time to write this about once a year....
In OD the final ratio for the WA580 is 0.83:1.0. the 580 is geared a bit more than most transmissions.... the 545RFE for example is 0.67:1. This means that the driven gear is effectively smaller than the driving gear--- and that smaller driven gear has a lot of force applied to its teeth, as all of that power is a) happening in higher torque/lower rpm b) limited number of teeth/surface area due to the affective size of the gear.
In a lower gear, yes there is indeed a smaller (relatively) gear driving a larger gear, however the forces are less because it is basically on the easier side of the gearing.
So in OD, all of that power is basically sent to a gear that is restricted in size. What happens? It heats up. It can become weaker via fatigue, and it heats the oil in the meshing surfaces more.
This was from a 4x4 mag decades ago. I don't recall which one, and they certainly explained it more elegantly than I can. However, I discovered what I think is verification of this in my Tundra once I put a scangauge on the trans temp. On level ground, with no shifting back and forth, and a significant tow load, the trans runs cooler when out of OD. It's a little difficult to detect unless you watch it in mine because at 180F the t-stat opens and engages the external cooler. But from what I can tell, this seems to hold true.
GRANTED, YMMV. Different trans are built differently. But as a general rule, it makes sense.
m
There is information missing in common "car lore" about why we are supposed you avoid OD. It's not Just the TC and fluid heat and clutch wear from that shifting. It has to do with the OD gearing itself.
I take the time to write this about once a year....
In OD the final ratio for the WA580 is 0.83:1.0. the 580 is geared a bit more than most transmissions.... the 545RFE for example is 0.67:1. This means that the driven gear is effectively smaller than the driving gear--- and that smaller driven gear has a lot of force applied to its teeth, as all of that power is a) happening in higher torque/lower rpm b) limited number of teeth/surface area due to the affective size of the gear.
In a lower gear, yes there is indeed a smaller (relatively) gear driving a larger gear, however the forces are less because it is basically on the easier side of the gearing.
So in OD, all of that power is basically sent to a gear that is restricted in size. What happens? It heats up. It can become weaker via fatigue, and it heats the oil in the meshing surfaces more.
This was from a 4x4 mag decades ago. I don't recall which one, and they certainly explained it more elegantly than I can. However, I discovered what I think is verification of this in my Tundra once I put a scangauge on the trans temp. On level ground, with no shifting back and forth, and a significant tow load, the trans runs cooler when out of OD. It's a little difficult to detect unless you watch it in mine because at 180F the t-stat opens and engages the external cooler. But from what I can tell, this seems to hold true.
GRANTED, YMMV. Different trans are built differently. But as a general rule, it makes sense.
m
Ahem, it would be a NAG1, which is essentially the same as a WA580 Mercedes trans but built in Indiana.
Note the NAG1 features variable lock up. The TC lockup is infinitely variable in every gear but first and reverse.
Known to be tough, but towing with it is a no brainer, no OD please...
Note the NAG1 features variable lock up. The TC lockup is infinitely variable in every gear but first and reverse.
Known to be tough, but towing with it is a no brainer, no OD please...
For the record the 09 Liberty doesn't use the NAG1 tranny, it uses the older 4 speed OD transmission. The NAG1 is a way better transmission IMO, and even then I wouldn't tow anything even remotely heavy in OD.
sorry-- I should have clarified--- I just pulled the 580/NAG as an example and the 545 as another strictly for gear ratio. Doesn't matter the unit--- the principle remains the same.
... and ... I am a huge NAG1 fan. it was probably the best part of the 08 WK I used to own. Fantastic trans.
... and ... I am a huge NAG1 fan. it was probably the best part of the 08 WK I used to own. Fantastic trans.
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