SoCalDesertRider
SanDiego, CA, USA
Senior Member
Joined: 12/14/2003
View Profile
|
I swapped the gears in my F350 from 3.55 to 4.56. It has 33" tires (285/75-16E). It also has a C6 auto trans that doesn't have an overdrive gear and the torque converter does not lock. The 4.56's were a HUGE improvement in towing and hill climbing performance, like night and day. It felt like I had swapped out the 351 engine for a 460.
The towing mileage improved. Local around town mileage close the same or slightly better. Unloaded freeway cruising mileage went down, but that's mainly because I don't have an overdrive gear.
My truck is 4wd and the gear change cost $2000, including $300 for a Powertrax Lock-Right locking differential for the rear axle. The work was done at a local axle and driveline specialty shop. Gears I used were Precision Gear for the rear axle and Dana Spicer for the front axle.
The gear change was very well worth the cost, made it a completely different truck, very happy with the gearing and still happy with it today. It's been about 5 or 6 years now since I did it, if I remember right. I would do it all over again if given the chance, but I would want to go a little more than 4.56.
If I had an overdrive gear, I would have gone with 4.88 instead of 4.56. With overdrive, there is still plenty of rpm range left in the engine to go 65 mph on the freeway with 4.88's and 33's and get descent mileage and 75 mph is still ok with the engine rpms, albeit at the loss of some fuel mileage.
92F350 CrewCab 4x4 351/C6
LoadNGo service body
69Bronco ATC250R CR500
20' BigTex flatbed carhauler
B&W TurnoverBall g-neck Curt Magnum rr DrawTite ft
HD springs Rancho9000s Bilsteins poly sway bushings
285/75-16E BFG AT on 16x8 Stocktons
4.56's & Lock-Rite rear
|
Carl_722
Warminster, PA
Senior Member
Joined: 02/01/2005
View Profile
Good Sam RV Club
 Offline
|
Would you do a 4.88 with the 245 or 265 tire?
2004 Chevy 2500 LT Crew Cab 6.0L, 4.10 gears 8600 GVWR 16000 lbs GCWR 10300 lbs tow rating.
2006 Crossroads Cruiser CF32BL 34'11" 3 slides.
Active Duty Navy
AWF1
NRA Member
Mosin Nagant M1891/30
|
LIKE2BUILD
Mt. Zion, IL
Senior Member
Joined: 09/30/2004
View Profile
Good Sam RV Club
Offline
|
I'm a believer in gears making a huge difference. However, GM did really choke these 6.0L engines with the torque management algorithm in the PCM. I have not personally used a custom tuned PCM, but there are several shops out there that can make these to nearly eliminate the torque management. You truck with 4.10 gears makes a good bit of torque in the 3800 RPM range. If you limit torque management you should be able to get nearly all of this to wheels and feel the truck pulling stronger.
KJ
2002 Jayco Qwest 324G
2004 Chevy 2500HD CrewCab |6.0L|2X4|4.10:1 | Eaton Posi-Trac
Curt MagnumV receiver
Eaz-Lift Hitch with Reese Dual Cam
1981 Seastar 18' Runabout
1996 Polaris SLT780 Waverunner
3 Wonderful Sons (10, 4, & 2)
1 forgiving wife!!!
|
Carl_722
Warminster, PA
Senior Member
Joined: 02/01/2005
View Profile
Good Sam RV Club
Offline
|
I am going to get a Wheatley tune most likely. He is on the Chevy Truck World Forum. I am currently using a hypertech tuner set for premium and it does make a large difference but I don't think it pulls back any TM. I think Diablo is the only tuner that does that.
|
SoCalDesertRider
SanDiego, CA, USA
Senior Member
Joined: 12/14/2003
View Profile
|
Carl_722 wrote:Would you do a 4.88 with the 245 or 265 tire? For my engine, I would not go 4.88 with 245's or 265's, but my engine has a much lower rpm operating range than your engine. My engine's peak torque rpm is 2800 and peak hp rpm is 4200.
Your engine operates 1000 rpms or more higher than mine. I would be willing to go 4.88 with 265's with your engine. Probly go 4.56 with 245's.
|
|
|
Carl_722
Warminster, PA
Senior Member
Joined: 02/01/2005
View Profile
Good Sam RV Club
Offline
|
I think I will need tires in the spring and I want to go up to 265/75/15 E in the Firestone Transforce HT I just took off the Transforce AT and didn't like them. I put my last set of tires Pep Boys tires Definity Dakota AT. I am done with AT tires. I don't have 4x4 and the AT's wear too fast pulling a camper. I am going back to a highway all season tire. Anyhow with that said I guess I would like the 265's because they look better and have a heavier payload rating also.
I am also thinking about the single 4" exhaust dynomax ultraflow. I found a comp cam that significantly increases the torque. I am researching what the best options for a cam right now. The gears I want now. The tires in the spring and the rest as soon as I can buy the parts and get busy. I have to do it when the weather is good so I can use the motorcycle during the down time.
|
Carl_722
Warminster, PA
Senior Member
Joined: 02/01/2005
View Profile
Good Sam RV Club
Offline
|
I found a precision gear set 9.5" ring gear for a 14 bolt 9.5 in a 4.56 gear for $189. I found a truck shop to do the work for $300. I just need to get the seals and shims. I think I am going to do it the beginning of December so it will be ready for my trip from PA to TN.
|
SoCalDesertRider
SanDiego, CA, USA
Senior Member
Joined: 12/14/2003
View Profile
|
Your truck should have a 10.5" 14-bolt rear axle if it is the heavy duty 3/4-ton. The 9.5" is not a full-float axle and was used in light duty 3/4-tons. It is basicaly a 1/2-ton axle with 8 lugs.
|
Carl_722
Warminster, PA
Senior Member
Joined: 02/01/2005
View Profile
Good Sam RV Club
Offline
|
I have the light duty 2500. I priced an axle from a junk yard for the 10.5 FF and they wanted $900 to $1,600 depending on use and the more expensive were rebuilt. But none had the 4.56 only the 4.10 and 3.73. If I could find a FF axle and leafs with the 4.56 gear for under a grand I would get it rather than change gears.
|
Carl_722
Warminster, PA
Senior Member
Joined: 02/01/2005
View Profile
Good Sam RV Club
Offline
|
The 9.5 14 bolt axle has only 80 lbs lighter GAWR than the 14 bolt 10.5. It is a SF but it has a higher GAWR than the 1500 axle which is only 8.5 10 bolt.
|
|
|
