towed my toy hauler to glamis last week [ 5 hr tow]. first long relatively flat tow. at 60-65 [ yeah i know i'm speeding] i'm right around 3k in third. the gap between 3-4 is huge, tried od but only feels right down hill. milage totally sucks, my truck has the power to pull a gear about halfway in between. looking at a gear vendor over/underdrive, kinda pricey, like the idea of a gear in between and a double od. i know it won't pay for itself, but for better towing manners and better milage with the double od when not towing think it may be worth it. any experience with these ? other options ?

 

Do you ever do any off roading? If you do, I'd say go for that underdrive. I have no experience with using them for towing applications, but for off road they rock. Don't forget that you will have to shorten or rework BOTH your front and rear drive shafts too. It get's pricey when you start adding it up.

What kind of RPM's are you looking at when towing in 3rd gear? If it's not over 3500, I'd just keep it in 3rd and let it spin, IMO.

 

What about switching to a lower gear ratio in the differentials?

 

That might end up almost as expensive as the over/underdrive.....the rear isn't that pricey but the front is CRAZY expensive to do....last time I asked I was quoted $1600 parts/labor for the front and $600 parts/labor for the back...and that was with the stock carriers, you add a Posi front and rear and you'd be at over $3100 for the gear swap

 

I may be off on prices but I think I saw the GV thing for about 2200 somewhere.

If you shop around you can find a better deal than that. Get you some gears off ebay for 400 front and back andget them installed by someone.

 

hey guys i'm back. i have a 1500hd 4x4 with 35's and 4.56 and a s.c. i'm at about 3k in third. with the s.c i feel like i can drag race in third but dogs in fourth. also with the 4.56 even with o.d at freeway speed i'd like to see lower rpms. the theory is i get the best of both worlds, a gear taller than third for towing and one above fourth for freeway, plus one between 1-2 and 1-3 three for closer ratio shifting. this is not an offroad underdrive there is no lower than 1st ratio and it does not function in 4wd, it was designed for towing and rvs, been around for years. there kit does not require front driveshaft mod or move the transfer case. it will be a month or so before they have one for my truck. when i get it in i'll let you know how it goes. p.s it's more like $3500 installed with rear driveshaft mod.