Posted 2005-08-11 4:16 PM (#29156) Subject: Towing in Overdrive
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Posts: 4
When driving with my gas engine automatics, I never pulled in overdrive. Recently purchased a dodge one-ton dually with a six-speed manual transmission. Other diesel drivers had been telling me that they pulled in 6th, otherwise the RPM's were closs to red-lining. I haven't tested this for myself, so do I pull in 5th or 6th?
Posted 2005-08-11 4:22 PM (#29157 - in reply to #29156) Subject: RE: Towing in Overdrive
Expert
Posts: 1416 Location: sc
6th.
i wont go into all the dynamics of autos/gas/diesel/manual, im sure someone else will. but a diesel w/manual tranny is a completly different animal, and a fine one at that.
Posted 2005-08-11 4:30 PM (#29158 - in reply to #29156) Subject: RE: Towing in Overdrive
New User
Posts: 4
I was hoping someone would say that. I just had a GM fleet salesman tell me that gas or diesel, it didn't matter, you never pulled in overdrive
Related question. Have also heard that I should be shifting without using the clutch to save on clutch wear. I have NOT tried this one either, though know it is possible, have no idea if it is particularly true. Opinions on this practice?
Posted 2005-08-11 4:34 PM (#29160 - in reply to #29157) Subject: RE: Towing in Overdrive
Extreme Veteran
Posts: 366 Location: Albany, Oregon
Originally written by chadsalt on 2005-08-11 4:22 PM
6th.
i wont go into all the dynamics of autos/gas/diesel/manual, im sure someone else will. but a diesel w/manual tranny is a completly different animal, and a fine one at that.
DITTO!
I have an auto and I pull in overdrive till I get to the steep hills then take it out. You will probably go to 5th about the same time. What is your gear ratio? 4:11's will pull better in 6th than the 3:73's.
Posted 2005-08-11 4:46 PM (#29161 - in reply to #29158) Subject: RE: Towing in Overdrive
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Posts: 2953 Location: North Carolina
Originally written by Jenkinsqh on 2005-08-11 3:30 PM
Related question. Have also heard that I should be shifting without using the clutch to save on clutch wear. I have NOT tried this one either, though know it is possible, have no idea if it is particularly true. Opinions on this practice?
Just My opinion... Unless you're very, very talented and in tune with your truck, Use the clutch. Clutch plates are cheaper by far than a tranny tear down and syncro replacement.
Again my opinion ... be careful of who you're listening to for vehicle advice. Two strikes so far.
Posted 2005-08-11 5:40 PM (#29164 - in reply to #29158) Subject: RE: Towing in Overdrive
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Posts: 1416 Location: sc
Originally written by Jenkinsqh on 2005-08-11 5:30 PM
Related question. Have also heard that I should be shifting without using the clutch to save on clutch wear. I have NOT tried this one either, though know it is possible, have no idea if it is particularly true. Opinions on this practice?
Thanks.
fact: all manual transmissions are designed to be used with the clutch.
that being said it is possible to shift a synchronized transmission without the clutch, why anyone would i dont know. you do take a substantial risk of RAPIDLY accerated wear. most clutch wear takes place from a dead stop, and IF used properly a clutch WILL last the life of the vehicle. but thats a whole other discussion.
as for how this type of stuff gets started.........big rig tractor/trailers have non-synchronized tranmissions, it is very simple to shift without using the clutch as it will NOT shift into the gear unless engine/road speed is exact. this is not recommended for these trans. either, but it is a common practice amongst the truck drivers(myself included).
Posted 2005-08-11 6:10 PM (#29167 - in reply to #29160) Subject: RE: Towing in Overdrive
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Posts: 455 Location: Ontario - east of TO
Originally written by xyzer on 2005-08-11 5:34 PM
DITTO!
I have an auto and I pull in overdrive till I get to the steep hills then take it out. You will probably go to 5th about the same time. What is your gear ratio? 4:11's will pull better in 6th than the 3:73
That's what I do too. I have a 350 Gasser/auto with the 4.10 and have found that when I did pull in OD (by mistake/habit) that the truck wasn't shifting out or changing gears so on level ground I haul in OD and shift to D for hills.
Posted 2005-08-11 7:43 PM (#29171 - in reply to #29156) Subject: RE: Towing in Overdrive
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Posts: 2689
I generally pull in the highest gear I can without LUGGING !
On downgrades I follow the truck rule of using the same gear as I would need going up. An alternative rule is the highest gear that will hold your speed down.
The Allison transmission has an algorithm built in for this, if you touch the brakes and the speed increases it will downshift, if the speed still increases it will downshift again - it has a limit built in to avoid overevving. It drops out of this mode when you press the loud pedal.
Not that I'm driving manuals much these days - I kinda miss 'em
Posted 2005-08-12 5:15 PM (#29177 - in reply to #29156) Subject: RE: Towing in Overdrive
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Posts: 326 Location: Palmdale, CA
I pull in 6th all the time, it's common practice. I always use the clutch. I downshift when the RPMs drop below 1800 and my EGTs start climbing above 1200. On a flat highway, I cruise around 65-70 in 6th, RPMs 2000, engine nice and cool. Just keep your RPMs around 1800-2200 and watch your EGTs. If trucks are redlining in 5th around 60mph, they most likely have the 4:10 rear end. Oh ya, and unless you are hauling or towing a load, start in 2nd.
With an auto, at least w/ the ones I've owned, I never tow in OD. Use 6th and don't worry about it.
Posted 2005-08-15 8:37 AM (#29210 - in reply to #29156) Subject: RE: Towing in Overdrive
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Posts: 225 Location: Kansas City
In my opinion you can tow in any gear you wish with a manual transmission as you are in control of the engine rpms, lugging, etc. You can see ahead and anticipate hills, grades, curves, etc. and a make "manual" adjustments as needed. Just as when you drive without a trailer you know when you need to shift up or down.
The reason to lock the over-drive out is to keep the auto tranny from kicking into "passing gear" as you accelerate up grades and then only to have it drop back out seconds later. This in-and-out cycle into overdrive causes much heat buildup. Pulling in overdive is really not the problem, it is the continual "auto" shifting which you have no control over.
Posted 2005-08-15 9:19 AM (#29213 - in reply to #29156) Subject: RE: Towing in Overdrive
Regular
Posts: 87 Location: Virginia
When we pull we always use OD as it states to do so in the manual, except in extreme conditions or you notice the tranny shifting in and out of OD a lot. We have a dodge dually with the cummins and an Auto Tranny with 3.55's in the rear and can usually use OD for most of our trips anywhere, until we hit the mountains then i drop it down out of OD and keep it in 3rd and she does great, creeps on the rpms but as long as i keep round 60-65 i'm okay.
First time we pulled our dually was with our gooseneck and we had the OD off and were on a straight away, wife was driving and i was reading the towing manual, i read that OD can be left on, so she clicked it back into OD and the dang rig jumped 10mph at the same rpm it was almost instantaneous. Love my truck, wouldn't trade it for nothing else, cept a Full Crew Cab Dodge.
Posted 2005-08-16 2:53 AM (#29256 - in reply to #29156) Subject: RE: Towing in Overdrive
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Posts: 189 Location: nashville, In.
OK guys. Don't beat me up if you have already answered this. I have a 2004 Duramax 2500. I think the rear end is 3:73 without having to look it up. I had a 2001 chevy 8.1 2500HD before and it only had the tow/haul option on the shift handle. I pulled with the t/h on and it out of overdrive.(showing on the gear options on the steering column). Now in my new truck it only shows Drive (D) on the steering column and 321. It has T/H on the gear shift and if held in longer the D in a circle with a slash in it. I take this to mean "not in overdrive" I hope this is right as I'm inside trying to remember how it is. Correct if I'm wrong. Nicely. Now, I have been pulling on the interstate with just the T/H on. It does not pull down nor does it shift back and forth. If and when I get into rolling and steeper hills (where I live) I do put it in the other also, (D w/circle around it with slash). I always have it in T/H but its the other I'm having trouble with figuring out.....and don't have husband or boyfriend to ask and then yell at if its wrong and something tears up!! Kidding!!! I won't blame you if I tear out my tranny..... And please explain it in simple terms, sometimes things get way to technical on here. Thanks in advance!
Posted 2005-08-16 9:23 AM (#29261 - in reply to #29256) Subject: RE: Towing in Overdrive
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Posts: 2953 Location: North Carolina
Originally written by inIndiana on 2005-08-16 1:53 AM
OK guys. Don't beat me up if you have already answered this. I have a 2004 Duramax 2500. I think the rear end is 3:73 without having to look it up. I had a 2001 chevy 8.1 2500HD before and it only had the tow/haul option on the shift handle. I pulled with the t/h on and it out of overdrive.(showing on the gear options on the steering column). Now in my new truck it only shows Drive (D) on the steering column and 321. It has T/H on the gear shift and if held in longer the D in a circle with a slash in it. I take this to mean "not in overdrive" I hope this is right as I'm inside trying to remember how it is. Correct if I'm wrong. Nicely. Now, I have been pulling on the interstate with just the T/H on. It does not pull down nor does it shift back and forth. If and when I get into rolling and steeper hills (where I live) I do put it in the other also, (D w/circle around it with slash). I always have it in T/H but its the other I'm having trouble with figuring out.....and don't have husband or boyfriend to ask and then yell at if its wrong and something tears up!! Kidding!!! I won't blame you if I tear out my tranny..... And please explain it in simple terms, sometimes things get way to technical on here. Thanks in advance!
P.S. This is an automatic.
Your Allison is a special case. It was designed to tow in overdrive (5th) Don't select another gear unless a special situation calls for it. You don't even need to select tow/haul unless your trailer is over 12,000 pounds. (75% of max)
I would recommend you put the selector in "D" and drive. Switch to T/H when the road is a hilly two lane or a lot of stop & go. The reasons are in the article below (for the techno geeks)
Tow/haul
The 1000 Series features a 12-inch torque converter equipped with an electronically controlled, hydraulically actuated, converter clutch. The (TCM) Transmission Control Module selects the gear for each drive range and engages the torque converter lockup. This is important: the TCM controls BOTH gear selection and torque converter lockup. It is NOT controlled directly by the column gear selector lever or the Tow/Haul mode button. The reason this is important is because you are not controlling single variables when you make input selections with these controls. You are changing several things at the same time. So let's look at what these inputs cause the TCM to do.
The gear selection (D, 3, 2, 1) input changes the shift point and the high gear as anyone familiar with an automatic transmission should be familiar, but it is further affected by the mode. The 1000 Series employs two modes of operation for GMC and Chevy trucks: Normal Mode When the truck is being used for normal day-to-day driving, and Tow/Haul Mode. Tow/haul mode is available for when the truck is loaded (a button on the end of the gearshift lever activates it).
The two modes are differentiated by three primary functions:
Although the second and third, Grade Braking and Shift Stabilization, interact with gear selection, these three functions comprise the difference between normal and Tow/Haul mode and so should not be confused with the gear selection alone. Let's look at the three functions:
TCC In normal mode, the TCC (torque converter clutch) is locked up in 4th and 5th gear. This provides for smoother up and downshifting when unloaded or with light loads, provides better fuel economy, and still provides for effective lockup under the higher loads of the upper gears (4 and 5). This is the best mode when the truck is at less than 75% of the GCWR.
In the Tow/Haul mode, the TCC is locked up in 2nd, 3rd, 4th, and 5th gears. Allison did this to avoid heat build up generated by a slipping TCC under heavy loads. This can occur when the vehicle and trailer are over 75% of the GCWR or under certain conditions such as frequent stop and go or steep hills.
Engine Grade Braking Engine Grade-braking helps the driver slow the vehicle and avoid excessive use of the brakes. For example, when drivers carrying heavy loads encounter a steep hill, they can manually shift into a lower gear for added engine braking to slow the truck. The 1000 Series collects operating data, including how long the driver's foot has been on the brake, vehicle speed, gear currently engaged, etc., and uses it to calculate shift parameters. At a certain threshold, the TCM of the 1000 Series will cause the transmission to downshift without the driver having to move the gear lever. Manual range selection is still available to the driver. Again, in the Normal mode, it will shift down from 5th to 4th. In the Tow / Haul mode, it will perform multiple downshifts from 5th to 4th, then from 4th to 3rd, using steadily lower gears to slow the truck.
Shift Stabilization Shift Stabilization uses the same type of advanced logic with input from the throttle position sensor, engine speed, and other factors. This feature detects and overcomes "shift busyness" that might be found in mountainous or hilly terrain. Algorithms housed in the TCM analyze the conditions, and when the parameters are satisfied it maintains the transmission in the lower gear for optimal performance. In Tow/Haul mode. the stabilizing effect this has makes driving a loaded vehicle considerably more comfortable.
As you can see, with the Tow/Haul mode, you are doing much more than telling the TCM to select a specific gear. The mode affects TCC lockup, the Engine Grade Braking program, and Shift Stabilization.
Posted 2005-08-17 2:19 AM (#29288 - in reply to #29156) Subject: RE: Towing in Overdrive
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Posts: 189 Location: nashville, In.
Hosspuller
Thanks for the explainasion. I even understood the techinal stuff! I build deisel engines and have test drove trucks with those engines in them, so I understand about torque and the grade braking.
Only thing is, just when would I need to ever use the D in a circle/slash option in the gear lever?
Posted 2005-08-18 5:27 PM (#29360 - in reply to #29288) Subject: RE: Towing in Overdrive
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Posts: 2689
Originally written by inIndiana on 2005-08-17 2:19 AM
Hosspuller
Thanks for the explainasion. I even understood the techinal stuff! I build deisel engines and have test drove trucks with those engines in them, so I understand about torque and the grade braking.
Only thing is, just when would I need to ever use the D in a circle/slash option in the gear lever?
Thanks
I VERY rarely use "overdrive lockout" on mine, sometimes if I know a long downgrade is coming up and I'm still in 4th and will want the engine braking.
I use tow/haul around town if I'm pulling anything much more than the 2 horse bumper pull trailer empty (about 3,000 lbs). When "rolling easy" I'll sometimes take it out of tow/haul just under 50 and back off the power so it shifts to 5th., then go back in tow/haul again to lock it up and keep the 5th at a speed it would normally use 4th for - the ~47 to ~55 zone.
So I guess my answer to your last question is, "When approaching a long downgrade, so it won't shift up to 5th and runaway on you." The rationale being that if your speed does start to build on that downgrade and you touch the brakes... ta dahh, you invoke another Allison "feature" if the speed increases again after the brakes have been touched.
I don't remember if HossPuller detailed this feature, but there are times when I would prefer it to not activate.
Towing in Overdrive
