Towing in overdrive

[funny farmer]

I was hauling some cattle in my wife's 16' avalanche horse trailer with my 88 F350 non-turbo,with 5 speed manual the other day. After a while I decided to shift into overdrive to see what it would be like. The trick did pretty good keeping up the speed but when I checked the mileage I was getting 11.5 miles to the gallon. Here's the question, would it have been easier on the truck, and would I have gotten better mileage running it in 4th at 2200 rpms? It was easier to drive in 5th at 1700, but it was a little doggy. I know the general rule is not to use overdrive if your pulling or hauling half the weight of the truck, but I've never been one to follow the rules. And I kept an eye on the water temp and it didn't go up or down either way.

 

[Diamondpilot]

I know in a auto its a definite no-no. A customer of mine has a 8,500# boat and was heading to the Lake of the Ozarks and he decided to switch to O/D. He boiled out the tranny fluid through the dip stick in 10 miles on his Dodge 3/4 ton truck with a 360 gas engine.

Look at it this way. You save 1 mpg at $2.50 per gallon. A tranny rebuild can run as much a $3500 these days so you do the math???? Keep it out of overdrive.

Chris

 

[FlaDon]

I know in a auto its a definite no-no. A customer of mine has a 8,500# boat and was heading to the Lake of the Ozarks and he decided to switch to O/D. He boiled out the tranny fluid through the dip stick in 10 miles on his Dodge 3/4 ton truck with a 360 gas engine.

Look at it this way. You save 1 mpg at $2.50 per gallon. A tranny rebuild can run as much a $3500 these days so you do the math???? Keep it out of overdrive.

Chris

Towing with mine in OD is no problem. All you have to do is put it also in Tow-Haul mode. But then mines an Allison. It's smart enough to drop into 4th if it needs to. It's also smart enough to kill the A/C compressor if it starts to overheat. But it never has. Worst it has ever done is kick in the thermostatic fan on the long 5% grade at 85°.

 

[radman1]

Towing with mine in OD is no problem. All you have to do is put it also in Tow-Haul mode. But then mines an Allison. It's smart enough to drop into 4th if it needs to. It's also smart enough to kill the A/C compressor if it starts to overheat. But it never has. Worst it has ever done is kick in the thermostatic fan on the long 5% grade at 85ｰ.

The transmissions in the newer trucks are much different than trannys of even a few years ago. Newer trucks don't have ODs like the older trannys which have a true over drive. My understanding is these older trannys lock into an overdrive gear with a small clutch. It is the frequent shifting into and out of the OD that causes a lot of heat and problems. The tow haul button on the older trannys locked it out of OD. Your allison, my 08 Ford and newer Dodge trannys have 5-6 shifts in the tranny. The tow haul mode in these trucks changes the shift points slightly and hold the rpms higher in a gear between shifts to help with towing and don't use a OD like the older units. My cousin, who new better, just burned up the tranny in his 03 Chevy 2 weeks ago pulling a load of lumber. Forgot to put in in tow haul mode. My brother in law did the same about 5 years ago with his F150 pulling an enclosed trailer. I had a mid 90's Ford Explorer that had the hot engine light come on pulling a small pop-up trailer. The radiator also helped cooled the transmission. The tranny got hot, heated up the radiator and caused the light to come on. Probably saved my tranny with the warning light.

 

[jagyzf]

I don't think heat will be an issue, if you read the 1st post the tranny is a manual. Heating is not an issue with a manual like it can be with an auto. So as long as he is not lugging the engine too much or the clutch was slipping, I don't see an issue. I do see where he might actually get better milage in 4th depending on the RPM's and if that is closer to the engines "sweet spot" than lugging it in 5th. I don't think a OD auto trans was an option in 1988 on an F-350, I don't think it was until 1990 or later but I could be wrong on that. The only 88 Diesel auto I drove had the 3 speed auto.

 

[George2615]

If you think you would have got better mileage running in 4th at 2200 RPM then run 4th gear. Using the 5th gear overdrive at 1700 RPM cut your mileage and lugged the engine.

 

[FlaDon]

The transmissions in the newer trucks are much different than trannys of even a few years ago. Newer trucks don't have ODs like the older trannys which have a true over drive. My understanding is these older trannys lock into an overdrive gear with a small clutch. It is the frequent shifting into and out of the OD that causes a lot of heat and problems. The tow haul button on the older trannys locked it out of OD. Your allison, my 08 Ford and newer Dodge trannys have 5-6 shifts in the tranny. The tow haul mode in these trucks changes the shift points slightly and hold the rpms higher in a gear between shifts to help with towing and don't use a OD like the older units. My cousin, who new better, just burned up the tranny in his 03 Chevy 2 weeks ago pulling a load of lumber. Forgot to put in in tow haul mode. My brother in law did the same about 5 years ago with his F150 pulling an enclosed trailer. I had a mid 90's Ford Explorer that had the hot engine light come on pulling a small pop-up trailer. The radiator also helped cooled the transmission. The tranny got hot, heated up the radiator and caused the light to come on. Probably saved my tranny with the warning light.

Mine is an 01. In automatics like the Allison, the OD(s) gearing is achieved thru clutch packs and bands applying on the planetary gearsets. The TC in the Allison ( pump per them ) is a lockup and the Allison can lock or unlock it in just about every gear. Shows up in tow-haul when the tranny drops into 4th from 5th at 2400 RPM and raises the RPM to 3200 RPM. If the load (torque needed ) is low enough, it locks back up and drops the RPM down to 2800. Sweet spot for torque on the big block is right at 3200. Even on the stretch with the 5% grades it still get the same MPG. Tranny temp stays the same as it does have a big cooler. Radiator temp will go up some until the fan kicks in. Then it drops back to 190.

 

[Builder]

Towing with mine in OD is no problem. All you have to do is put it also in Tow-Haul mode. But then mines an Allison. It's smart enough to drop into 4th if it needs to. It's also smart enough to kill the A/C compressor if it starts to overheat. But it never has. Worst it has ever done is kick in the thermostatic fan on the long 5% grade at 85ｰ.

Aren't they great? Mine's never seen more than 190* on the hottest days.

Other than DP's GM that everything broke on, just about everyone else that owns & operates an Ally loves them. Mine feels like a tank. I wish my 4800 had an Ally.

I was hauling some cattle in my wife's 16' avalanche horse trailer with my 88 F350 non-turbo,with 5 speed manual the other day. After a while I decided to shift into overdrive to see what it would be like. The trick did pretty good keeping up the speed but when I checked the mileage I was getting 11.5 miles to the gallon. Here's the question, would it have been easier on the truck, and would I have gotten better mileage running it in 4th at 2200 rpms? It was easier to drive in 5th at 1700, but it was a little doggy. I know the general rule is not to use overdrive if your pulling or hauling half the weight of the truck, but I've never been one to follow the rules. And I kept an eye on the water temp and it didn't go up or down either way.

​

I'm assuming your's is a ZF-5 manual. They have a .77 O/D on the close ratio and .76 on the wide ratio transmissions. In 4th, you're running 1 to 1.

My question is-did you check the fuel economy when you were in 4th gear?

 

[wushaw]

My 03 3500 DMAX/Allison saw 230 going down hill and 230 on both tranny and eng going back up the same hill in Colorado...it was a big hill. The Ally is the best automatic tranny I have ever had the pleasure to use but it aint bullet proof...yet.

 

[patrick_g]

The water temp gauge is good to monitor BUT... a heavy load pulling up a hill and you could damage a diesel engine before the radiator temp would rise enough to alarm you especially if you aren't exactly stock.

You get a much better indication that responds more quickly by using an exhaust gas temperature (EGT) gauge, a pyrometer installed in the exhaust.

I could seriously overheat and potentially melt the top out of a piston under certain conditions if I ignore the pyro and rely on the water temp indicator.

Pat