Transmission Question

[woyster_00z71]

Ever since I got my bigger tires put on my Tahoe, it has felt a little underpowered. I knew this would be the case with a 3.73 rear end and 315's. Anyway, I have been driving with the gear shifter in 3 until I get over 50mph just because I don't like the tranny shifting in and out of overdrive and because it is very sluggish in OD. Yesterday I tried driving around in Tow/Haul mode to see if that was any better. Although it seemed to be more responsive and less sluggish my question is, Is it OK to drive in Tow/Haul mode everyday when not towing/hauling? The only thing that bothers me is the higher rpm's in each gear before it shifts and it waits untill 60+mph before shifting into overdrive.

 

Or should I even worry about it all-together?

 

Thanks,

B.J.

[SilveradoWV]

I dont see a problem running in 3 like you had been doing! Not sure about tow/haul!

[carl722]

If it bothers you to drive in OD just drive it in 3rd gear. I do that with mine on the interstate in the city too andit does't hurt a thing. 3rd gear is what used to be Drive which is a 1 to 1 ratio all it does is potentially lower your gas mileage but if your ters lug it down so much you may get better mileage in 3rd because you are in your torque and power curve. where the engine doesn't labor as hard to speed up or have to kick out of OD to speed up. What is the aspect ratio of your 315 are they 65's or 75's. If they are 65's they are roughly 33 to 34 inch tires. I have 285/75/16 on my truck they are rougly 33 and they definetly drag on the 3.73 gears. I don't know about my mileage though I usually get 11 or 12 mpg. in town and I have got 15 on the interstate for long trips.

[Markeaux]

I run tow/haul mode most of the time in the city and stop/go traffic. Also, letting the engine get up farther in the rpm's a lot is probably good to help keep carbon buildup down in the combustion chamber and help reduce pinging).

[JayMan]

I run tow/haul mode most of the time in the city and stop/go traffic. Also, letting the engine get up farther in the rpm's a lot is probably good to help keep carbon buildup down in the combustion chamber and help reduce pinging).

 

I do the same. The owners manual and shop manual tell you there is no harm in using Tow/Haul, though the shift quality might be "objectionable."

 

What I like is the fact it's a push-button Shift Kit. There are times when I want silky-smooth shifts, so I leave Tow/Haul off. When I want to keep the RPM up, especially in hot summer A/C town driving or very cold winter town driving, Tow/Haul stays on. This way you don't have to move the column selector by hand.

 

I tried a shift kit back in 1985 in my 1984 Ford F-150 with 302 and C6 auto. With the Edelbrock 289 intake and a Holley 4 barrel, shifts were great at full loads or full throttle. Otherwise it shifted like a garbage truck. Finally got rid of the shift kit for that reason.

[gunslinger45]

It is recommended by some that it is good to lock out overdrive while driving in the city. When the tranny shifts into overdrive, the tranny will not circulate as much fluid as in the lower gears thus reducing the cooling function of the fluid. Less fluid circulating equals less heat transfer. So, as was mentioned before, if you don't mind a slight hit in gas mileage, then driving around in town with the trans locked out of overdrive (in 3rd) you will probably be easing the load slightly on tranny. There was a large post on another website where some tranny expert (personally cannot vouch for him) stated that driving around town in overdrive was one of the worst things for a big tranny mainly due to the decreased ability to remove heat from the unit.

 

As for the Tow/Haul mode, it firms up the shifts reducing the time the clutch plates slide against each other and thus reducing wear, so if you don't mind the firmer shifts, it too is a good way to take some stress away from the tranny. It won't lock out overdrive, but it will move the shift points up and I doubt you will hit overdrive during city driving with it engaged, so leaving your truck in Drive, but engaging the tow/haul mode may be the easiest way to get most benefit. Minimal overdrive during city driving allowing better cooling and firm shifts which slightly reduce wear in the tranny. Downside, little bit less gas mileage.

 

Gunslinger