4.56 vs 4.10 Gears

[Recovry4x4]

I have an opportunity to select either gear ratio for my contact converted M1008. I would normally advise folks to just stay with the 4.56 but there are other factors pulling me towards the swap. At 2800rpm, I would gain 6 MPH. My concern is losing acceleration and towing capacity. Has anyone else done this swap? I know folks that have done the 3.73 swap and noticed a significant reduction in pulling power and acceleration. My main draw for this is swapping for a cab and chassis axle. I plan on either a 700R4 swap or an SM465 swap in conjunction with a Ranger Torque Splitter overdrive sometime in the future.. The 700 has 30% OD and the splitter has 27%.

 

[AECS]

The 700 has a lower first gear, so you will be getting some of your low end back from the 4.10 gears, the difference should be negligible, unless you are towing 10,000 up a mountain, that seems like a great combination, the 4.10 and 700...

 

[Lonnie]

The 700R4 has a large drop in OD, so the 4.56 will work out to a decent cruise ratio in OD.
I used to run my Chevy truck with 35" tires & a built 427 with a 700R4 & it was a good combination.

Tire size has a lot to do with gearing also, but the overdrive allows you to have the best of both worlds.
Also remember the 700R4 has a much deeper first gear than the TH400... 3.06 vs. 2.48, to help out your low end.

 

[kblazer87]

All things considered, if you don't mind shifting gears manually I believe the SM465 would be the way to go.
If you look at the gear ratios for the manual, they are much better than the autos and when you factor in the Ranger overdrive it would rival the NV4500.

Ratios for the SM465:
First Gear - 6.55:1Second Gear - 3.58:1
Third Gear - 1.70:1
Fourth Gear - 1.00:1
Reverse - 6.09:1
With those ratios you could drop to 3.73s and still have good acceleration and pulling power so 4.10s would be even better. Automatics are nice and a lot of people don't like rowing gears manually, but I guess I am a throwback.

 

[wheelspinner]

My ton axles I have for my 1009 have 4:10s. Watching this to see where it goes.

 

[hndrsonj]

I'd go 4:10.

 

[patracy]

I think you'd be fine. I had a 700R4 behind a 350 feeding 4:10 gears in a suburban on 33's, seemed perfect to me.

 

[61sleepercab]

I ran 3.73 gears in a re powered Jeep pickup and hauled 3+ tons of gravel with no problems. I have a Chevy 1 ton with 4 speed and 4.10 gears are too slow for Interstate speeds. I would suggest for balance of empty/ hauling to go with 3.73 Mark

 

[Chaski]

What size tires do you plan on running?

I had a 700r4 with stock tires and 4.10 gears. I thought it was perfect.

If you go with 33-37" tires I'd go 4.56.

Stock tires, 4.10 gears 4l80e 60 mph 2068rpm, 75 mph 2585rpm.
Stock tires, 4.10 gears 700r4 60 mph 1930rpm, 75 mph 2412rpm

Add 10% engine speed for 4.56 gears. Subtract for larger tires, numbers were figured with 30" tires.

 

[Castle Bravo]

I had a '94 Suburban with a 4.10 rearend and a 4L80 with a 6.5 turbo engine, and it seemed like it wasn't really suited for highway speeds. It seems like it was over 2500 RPM to go 75 MPH. It had 245/75R16 tires.

 

[Recovry4x4]

Tire initially will be 235/85R16 but later will be 255/85R16. I've crunched the numbers on the swap. I'm only concerned about the loss of pulling power with my beloved but anemic 6.2. I think I am going to try it. If it isn't what I thought, I'll swap everything to the flatbed project.

 

[Westech]

I have 3.08's in my M1008 and she still has a TON of low end. Also I am able to run 65+ MPH with ez.
Now I do have the stock TH400. With a OD trans the 3.08's would be too tall until 80 MPH and at that speed that 6.2 will be running out of juice.
Spedman has a TH700R4 in his truck with 4.56 gears and loves it. I have rode in it a few times and it seams VERY drivable.
For the hassle I would just keep the 4.56 gears.
Side note... 4.56 gears with sustained 70 MPH + may cause a overheating of the axles and Transfer case. I would add axle cooler covers (finned) and use DexV in the transfer case.

 

[Recovry4x4]

The main reason I am drawn to this is to get the cab/chassis rear end. It's already 4.56 and I know what I have. I have also owned an M1009. Power and acceleration between the 3.08 and 4.56 can't be compared.

 

[Westech]

Point being: I dont think you will notice a difference between 4.10 and 4.56. It will drop the RPM's a little and thats it.
Cost effectiveness: Not worth it.
You would need to do a drastic change like I did on my M1008 with the gears to make a difference.
I would not change to 3.08's if you are towing 5000+ pounds or loaded with equipment.

Are you adding the hub spacers to the front axle to make it a true dually if you are going to use the dual rear end?
I have seen dually conversions with stock front axles and it does work and look fine to me.

 

[Chaski]

Tire initially will be 235/85R16 but later will be 255/85R16. I've crunched the numbers on the swap. I'm only concerned about the loss of pulling power with my beloved but anemic 6.2. I think I am going to try it. If it isn't what I thought, I'll swap everything to the flatbed project.

Good choice.
I have 4.88's with 37" tires, it is almost the same as 4.10's with 31" tires. With the 700r4 it almost makes that 6.2 snappy off the line. Also seems to be "right" when pulling mountain grades at highway and freeway speeds.

 

[wcuhillbilly]

Point being: I dont think you will notice a difference between 4.10 and 4.56. It will drop the RPM's a little and thats it.
Cost effectiveness: Not worth it.
Agreed.....

You would need to do a drastic change like I did on my M1008 with the gears to make a difference.
I would not change to 3.08's if you are towing 5000+ pounds or loaded with equipment.

Are you adding the hub spacers to the front axle to make it a true dually if you are going to use the dual rear end?
I have seen dually conversions with stock front axles and it does work and look fine to me.

You would love my daily driver......
85 Crew cab 4x4 dually Cab and Chassis........ Previous Driveline was---- 6.2 (turbo'd) Ranger Torque splitter, SM465, NP205, Cab/Chassis dually 14b with 3:73 gears. Tires,,, 235/85/16.

I had 4:56 in that same rear but swapped to 373 for a highway leg, as I had a gasser with the same trans ratio and 4:10s and knew it would put the 6.2 out of its power range while running highway speeds. THus I swapped in 3:73 when I built this one. I put about 35k on this driveline before swapping in the Cummins/4500/205 in my sig.

I loved and hated the previous driveline. The 6.2 was slow and didnt like the weight of the truck with the 3/73. Once I turbo'd it there was a night and day differance. It was chugging up hills empty in 3rd gear at 25mph where now I could hold 55 or 60 unloaded. Still the 4th gear limited me to a top end. Later I put the Ranger in and another world opened up. I could hit 80 on the open highway and was getting mid 20s for fuel milage,,, yes no joke. I left Moorecroft WY and swapped tanks (20gal) a little south of Fort Collins Co. after running 65/70mph all the way. (at that time the weight of the truck was just under 7K.)
My final decision for swapping the 6.2 for a Cummins was hauling a 1970 K20 on a flat bed out of Glenwood Springs Co up and over Vale/Eisenhaer pass and back to Golden, My pyro hit 1250 and temp hit 250 and strange things were happening with power loss as it got hotter, I was in 2nd gear Ranger high, as we slowly climbed up to the tunnel.....

I loved the ranger coupled to the 465, giving me 8 forward gears and 2 reverse speeds, making backing up to trailers nice, If you need even more creep, put a 2 stick on a 205 and you will have the ultimate reverse. slow enough to start it back and get out and check once in a while...

There is nothing special about the cab/chassis (C/C) rear,,, the differance is in the hubs,,, thus if you really want the space differance, rob the hubs/backing plates off a C/C axle... We tubbed the bed of my box to fit the duals, and everyone asks me if it came that way from the factory, duels under the bed and no hips... I just smile and say, "Yup, its cheaper when you go up to the factory and say,,, pick it up yourself"

Turbo,,, I advise the GM-3 found pre 94 on 6.5 trucks, this turbo was mechanical and controled by a can on the side of the mount,,, this can has a big spring in it... just carefully cut the can away and save the spring , now thread the end of the rod and reinstall the spring with a washer and a nut, this will alow you to vary the boost up to the safe point of 12-14psi.. next turn the fuel screw counter clockwise in the injection pump (little 3/16 or 1/4 allen)(its been 11 years ago).

With the turbo'd 6.2 the ranger/465/205 with 3:73 gears that I was running the 6.2 stayed happy at around 2400rpm at 65-70mph. and made a great daily driver with great milage, and plenty of power for light to moderate loads. just wouldnt advise any high mountain passes carrying any K20s

If you or anyone needs to ask questions about this or anything I may have mentioned before, Feel free to PM or give me a call, as I dont mind helping out fellow gear heads.
Joe S. 307-282-0773

 

[amgeneral72]

I also have a cab & chassis rear end with a 4.10 set-up. I was going to swap it in to the M1031. The problem was the inside tire would hit the box. I guess I could cut the box.

Any thoughts?

 

[wcuhillbilly]

I also have a cab & chassis rear end with a 4.10 set-up. I was going to swap it in to the M1031. The problem was the inside tire would hit the box. I guess I could cut the box.

Any thoughts?

I just edited my post,,, as I usually time out while responding and thus loose all my work,, so I post it then go back and edit it a couple times to stay withing the time constraint, thus you probably didnt see that mine is tubbed some, and folks always ask how I got those duals to fit.. Tubbing is easy, just cut the well down the middle and move it inbord some and add about 4" to the middle... once youve done one the other is simple.

 

[Recovry4x4]

Thanks guys, much great info. I am aware of the similarities of the chassis cab rear. One of my options is to relocate the backing plate mounts and use the CC hubs. If I do this 4.10 swap, I will swap entire axle assemblies with a friend. Costs will be minimal unless I find issues in the axles. I will also keep my Detroit NoSpin. If I were to redo it with CC hubs I would just swap out front rotors. I do have an extra set of those.
As a matter of fact I have a 205 with brand new twin stick rails and a cable shifter.

Drew, my body has a frame rail in the way as well. I'm going to mod it a bit and add an add a leaf.

Remember, I just did this CC swap.

 

[Recovry4x4]

OK, the deal was struck. In a few weeks my M1008 with the Dodge contact bed with have duals with a cab/chassis 14 bolt.