Overdrive advice please

[kenmyfam]

Well I have the new to me tow vehicle after the Windstar fried it's transmission last trip.
I now have the following tow vehicle.
1999 GMC Jimmy SLS
Towing around the 2,000 lb mark.
Planning a trip friday for the long weekend camping and boating (and drinking after the boating is done for the day)
My question is, trip is around 200 miles each way.
Should I be towing in overdrive or not ????
I am running a little scared after my recent Windstar experience when i fried the tranny at the 140,000 km mark !!!!
Thanks for any and all input.

 

[evilratgirl]

Re: Overdrive advice please

First, that Windstar has nowhere the towing capability of the Jimmy.

You don't mention if the Jimmy is 2x or 4x which will effect the towing slightly. With towing 2K you should hardly feel the boat except on hills. Personnaly I don't ever care for towing in overdrive. But there are exceptions. A light load on fairly flat ground being one.

The owners manual states that when towing and it hunts between gears to take it out of overdrive. That to me is the real bottomline. As I mentioned, you don't want it in overdrive if towing in hills.

 

[kenmyfam]

Re: Overdrive advice please

It is a 4 X 4 but I would rather tow it in 2WD if possible.

 

[Silvertip]

Re: Overdrive advice please

You cannot tow in 4WD HI unless you have the automatic 4WD system. The manual systems do not have a differential in the transfer case and you will break things on dry roads. The reason you were asked if it was 4WD or 2WD is the gearing on the two vehicles is different and because of the added weight of the 4WD system, the tow ratings are slightly different but that doesn't affect you in this case. What does affect you however is the axle ratio. I'm guessing, but the standard ratio in most of those vehicles. 3.54:1. 3.73:1 and 4.10:1 axles were available as options. If you have the 3.73 ratio you can indeed tow in overdrive with exception being if the torque converter unlocks frequently, you best run in direct. I would not tow in direct (3rd) if you have the 3.54 axle. My fishing buddy and I both have S10 Crew Cabs and we both tow identical boats. His has the 3.54 gears, mine has the 3.73. He cannot tow in OD and I can. You will not hurt anything towing in direct, but you might in OD if the gearing is wrong. The only way to know is try it and pay attention to the torque converter. If you don't know what that feels like, drive at a steady 50 mph and while holding the gas pedal steady, GENTLY touch the brake pedal with your left foot. Watch the tach. You will see rpms increase. Release the brake and the tach will drop again. With the trailer on, that would feel like a gear shift but it's not.

 

[kenmyfam]

Re: Overdrive advice please

You cannot tow in 4WD HI unless you have the automatic 4WD system. The manual systems do not have a differential in the transfer case and you will break things on dry roads. The reason you were asked if it was 4WD or 2WD is the gearing on the two vehicles is different and because of the added weight of the 4WD system, the tow ratings are slightly different but that doesn't affect you in this case. What does affect you however is the axle ratio. I'm guessing, but the standard ratio in most of those vehicles. 3.54:1. 3.73:1 and 4.10:1 axles were available as options. If you have the 3.73 ratio you can indeed tow in overdrive with exception being if the torque converter unlocks frequently, you best run in direct. I would not tow in direct (3rd) if you have the 3.54 axle. My fishing buddy and I both have S10 Crew Cabs and we both tow identical boats. His has the 3.54 gears, mine has the 3.73. He cannot tow in OD and I can. You will not hurt anything towing in direct, but you might in OD if the gearing is wrong. The only way to know is try it and pay attention to the torque converter. If you don't know what that feels like, drive at a steady 50 mph and while holding the gas pedal steady, GENTLY touch the brake pedal with your left foot. Watch the tach. You will see rpms increase. Release the brake and the tach will drop again. With the trailer on, that would feel like a gear shift but it's not.

Thanks for that. I will try to check out the axle ratio but if I can not find it then I think i should tow in direct to be certain. Does that sound like a good idea ????

 

[tashasdaddy]

Re: Overdrive advice please

if you are in hilly country, definately direct. in the flats of Florida we use the OD, and it will come out sometimes on the interstate overpasses, but thats it. went to North Carolina, had to use direct.

 

[Ralphy]

Re: Overdrive advice please

I have an 04 Blazer 4x and owners manual says do not tow in OD. Put in 3rd as it will raise your RPM's a couple of 100 and in doing so more flow through the transmission which helps keep the tranny cool.

 

[Mike V]

Re: Overdrive advice please

using overdrive while towing is a bad thing (the heat it generates is actually the bad thing) direct is the way to go if you plan on having a healthy transmission. as it locks the torque converter in position instead of jumping gears often and causing alot of wear and tear.
Have an excellent trip!
MV

 

[KM2]

Re: Overdrive advice please

Read your owners manual first! My vehicles both say its ok to tow in OD unless the transmission shifts frequently.

Now with a light load and low wind resistance, 3.73 or lower gears that truck should pull OD on flat ground no problem. Some good advise was given in early posts about detecting the converter unlocking/locking.

With a light load using overdrive will help MPG, on heavier loads the difference is very small in my experience.


Kevin

 

[mrfixitman40]

Re: Overdrive advice please

the best way to know wil be try and see if the converter is locking and unlocking if it is staying locked you won't have a problem in od I personally tow in od all the time but i am towing with a v8 not a v6 the converter is what produces the heat nothing else and if you notice it is in and out of lock then pull down to direct and it should allow lockup due to the rpm and pressure . Is this a factory tow package or add on if it is an add on i would recommend a trans cooler be installed also.

 

[kenmyfam]

Re: Overdrive advice please

Got a hold of the owners handbook from the guy I bought it from today and it recommends towing in "3" and not overdrive. So i guess that is what i will be doing. Thanks to all for the info and advice. I can put up with a higher fuel use if i know I am going to get where I am going (and back again)
If anyone has any other opinions or advice please let me know.
Thank You,
Ken

 

[demsvmejm]

Re: Overdrive advice please

If you have a Tow/Haul mode for the transmission then it is acceptable and recommended to tow in overdrive. Otherwise, regardless of what the owners manual says, any good tranny shop will tell you to keep it out of overdrive. As for the axle ratio, you can either check what are called the "RPO" codes or Regular Production Option codes. You will need to have access to a code list. Or you can take the VIN and call the dealership parts department. They should be able to tell you what axle ratio, ring gear diameter and axle model you have. Have fun and a safe trip.

 

[kenmyfam]

Re: Overdrive advice please

If you have a Tow/Haul mode for the transmission then it is acceptable and recommended to tow in overdrive. Otherwise, regardless of what the owners manual says, any good tranny shop will tell you to keep it out of overdrive. As for the axle ratio, you can either check what are called the "RPO" codes or Regular Production Option codes. You will need to have access to a code list. Or you can take the VIN and call the dealership parts department. They should be able to tell you what axle ratio, ring gear diameter and axle model you have. Have fun and a safe trip.

Thanks for that. It does not have a tow/haul mode so I will be keeping out of overdrive. I will also check for the axle ratio with your advice.

 

[jtexas]

Re: Overdrive advice please

Wonder if mythbusters would take on this question.................

 

[DaveM]

Re: Overdrive advice please

Got a hold of the owners handbook from the guy I bought it from today and it recommends towing in "3" and not overdrive. So i guess that is what i will be doing.

Me thinks you found your answer. My manual for my 1994 GMC K1500 clearly stated to not tow in OD. It was in perfect running order and all origianal after 12 years and 150,000 miles, even though those in the know said those trucks where built with a weak transmissions. I never had a problem, but I did keep up with fluid changes. My new truck manual says it is OK to tow in OD, but that Allison is much stronger.

On a side note, I wonder out loud how much of an improvement in mileage would one get by towing in overdrive. Considering that any given tow vehicle gets crappy mileage running empty, then add several thousand pounds (or kilo's) of dead weight. Curious minds...

 

[ktmrider]

Re: Overdrive advice please

just get a diesel and be done with it....

 

[kenmyfam]

Re: Overdrive advice please

Well, i am heading for Conestogo Lake tomorrow afternoon. I will be towing in "3" as stated in the manual and will report back late Monday or Tuesday. I weill also be checking the mileage I get as the fuel gauge is a little dodgy !!!!!

 

[kenmyfam]

Re: Overdrive advice please

Fuel gauge read half this morning and I filled it up with 65 litres in a 72 litre tank !!!! Will be checking the miles per gallon for future reference !!!!! so as not to run out !!!!

 

[Silvertip]

Re: Overdrive advice please

You will see about 2 - 3 MPG difference if you can tow in OD. Depends on whether or not you have the A/C on and whether you are running into a headwind, have a tail wind, hilly or flat roads, etc.

 

[kenmyfam]

Re: Overdrive advice please

You will see about 2 - 3 MPG difference if you can tow in OD. Depends on whether or not you have the A/C on and whether you are running into a headwind, have a tail wind, hilly or flat roads, etc.

Personally I do not care how much it uses !!!! as long as it gets me there (and back) !!!!! but I will report back how I go on. We are all loaded and ready for the long weekend with approximately 2,000 lb to be hauled (camping gear etc) some gear in the back of the Jimmy and some heavier stuff in the Grand Prix. (Yes we are taking 2 vehicles as we have 5 children plus significant others) maybe 3 or 4 vehicles !!!!!
Looking forward to a great weekend with the family and plenty of tubing and ski-ing !!!! a lot of beer and a memorable camping experience !!!!