Reply to thread

Message: [QUOTE="Kowboy, post: 1538771, member: 29363"] I have an OBS with a ZF-5 42. The factory gears were 4.11 with 33" tires. I have owned the truck for 24 years, about 5 years ago I had 3.55 gears installed, before at 2000 RPM in OD I was at 58 MPH, now at 2000 RPM I am at 70 MPH, but I could no longer start off in second gear. I had to always use first. If I was loaded heavy 10 - 12000 lbs on the trailer and I was on a hill I had to put the transfer case in 4 low. I was not liking this at all, neither was the clutch, I was debating on going to 3.73. I started looking at options and decided to install a ZF-6. Going to the 6 speed is night and day verses the 5 speed. It has made driving the truck a joy again. Empty I can start in 2nd again and even did 3rd once when I was not paying attention. I say all this to make a comment to my experience. I was hoping to be able to cruse at a higher speed on the highway and get better MPG. I can cruse at a higher speed but there is no MPG improvement. I attribute that to the fact that I am going faster and there is more wind drag, when I am stuck having to travel at 55 - 60 I do see a gain in MPG. I am very pleased with the 3.55 gears and would do it again. But consider the primary use for your truck. I think that when I am loaded I might get better MPG with the 3.73, but I am not willing to spend the money to find out. Good luck on your decision, When you are done let us know how you like the change. [/QUOTE]

Verification

Random media

Picture_780

trucks1

Picture_175

2012-03-27_15-11-13_539

Built_Up_Motor_1

Always changing to make it a home on the road.

Hole_in_Piston_from_Top

08 door handles

psa_camo_blk

Latest posts

I must be getting old… Exhaust is too loud
- Latest: Derkperk
- 24 minutes ago
6.0 Aftermarket
T
B&W hitch and shock removal
- Latest: TexMac
- Wednesday at 2:48 PM
2017+ 6.7 Aluminum Super Duty
6
ISSUES WITH CHOATES WARRANTY
- Latest: 6.7powersmoke
- Wednesday at 2:12 PM
1999-2015 Superduty Series General
Truck slipping into 4th
- Latest: Sterling6.7
- Apr 25, 2025
6.7 Tech
Do not recommend Choate Engineering
- Latest: DEEZUZ
- Apr 23, 2025
Newly Enlisted

Members online

No members online now.

Total: 239 (members: 0, guests: 239)

Top