v8 4l60e 35s Gearing Question

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Feb 28, 2008
Like the title said I'm trying to decide on gearing. I have a 5.7tbi 4l60e split case and stock gears soa on 35s. The 3.73s honestly don't even bother me but I know it would be better with at least 4:10s or 4:56. Calculating it out it seems ideally to get stock gearing like a suburban I would want the 4.10s
a 2wd burb came with 3.43 and 29 inch tires. a 4wd came with 31' tires and 3.73 so 35s and 4.10s keeps the rpms almost the same as a stock burban.

The cruiser weighs 1000 lbs less.

My questions is for those with a v8 and 4l60e split case specifically what is your real world rpms with your gears.

Mainly 4.56 , 4.10 and 4.88.

My main concern is to get a good highway ratio with the ability to tow 5k. With the auto offroad gearing between 4.10s and 4.56 doesn't concern me. for what I do 3.73s in low range is fine.
honestly 3.73s 35s and 5 k around town is a non issue but I know 5k with 3.73s would suck in the hills. Plus there is defiantly a difference in an open and enclosed trailer. 3.73s unloaded get great mileage so I don't really want to go any higher than I have to. I get 16-17 on the highway. tbi motors make their peak torque and hp pretty low for a gas motor as well.

My 24ft enclosed trailer is 3500 lbs empty my rail weighs 1200lbs max and the rest of the bikes and cargo will never be over 800lbs. brakes on all 4.

While I'm at it. Limited slip vs a full locker for mainly sand use?
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Remember it's important to stop too... You are going to need to upgrade your braking system in my opinion if you want to tow that much weight.

I would go 4.56 or 4.88s.
I had that set up 3.7 gears and 33's after 2.5 years of travels with my trailer the tranny gave out... (dont know if it had anything to do with it). I now run 4.11 and a beefed up 4L60E. I would suggest going to at least 4.11 or lower.. your RPM will go up and your mileage will go slightly down..but keeping the speeds up on grades will be a lot easier on your tranny.
I would suggest going around talking to transmission peeps... I was told bigger tires and low gears kills the life of your tranny by almost half. when I got me tranny rebuilt with upgraded gears and servos I was also asked the weight of my rig and the size of tires I would be running....
I dont know much about transmissions but I can tell yah Im happy with the way mine runs on 35's and 4.11's.

Good luck...
Stopping isn't to much of an issue. The trailer itself will stop my 2500hd fully loaded which is around 10k when I use my truck to pull it if I crank the brake controller up.

Manuchao so you went 35s and 4.11s at the same time and that setup did feel better than the 3.73 and 33s?
I had the trans beefed up when built as well. It shifts pretty firm which I wanted when I had it built just in case it ever
You can usually go a ratio taller with an auto than you would with a manual. My vote would be 4:10s. Easy to get, you don't have to grind anything to make them fit in the carrier and taller ratios are stronger due to the higher amount of gear interface.
mine is 5.3 4L60E 35 Krawlers and my 4.10's are OK empty ... BUT suck flat towin my 40 so I'm tossing in 4.56's ... as stated my powerslot rotors and V6 calipers stop better with 35's then the stock stuff with 33 :) ... trailer brakes only do so much my 60 with 33 trailer brakes and the truggy ...was scary
Cool. I think I'll probably stick with te 4.10s since its a tbi. A tbi makes its max hp at 4k and is max torque at 2800 rpms as apposed to 5200 rpms and 4000 rpms for the newer vortec. 4.10s and 35s should get me about 3200 rpms out of overdrive.

I know my 6.0 has a lot of power at 3500 rpms and a ton of power at 4500 rpms. I think 4.56 will fit that 5.3 quite well. In fact when I tow up to the mountains I'll drop to 70-75 and see close to 5k on the tack but it will rip up the hill with 8k behind it. The 5.3s seem pretty similar from the ones I have driven.

I'll defiantly give the trailer a good shake down run empty to check everything out. Its a 08 haulmark 24' with 5200lb tandem torsion axles and brakes on all four. I use a prodigy controller and i'm pretty happy with that setup. At 9-10k weight i notice almost no additional effort to stop the 2500hd. It'l only be half that weight behind the cruiser.
When I re gear i might as well throw those rotors and the four runner calipers in while i'm at it. sounds like its a worthwhile upgrade. The rest of the brake system is new. Completely new drums shoes wheel cylinders, new master, 4 runner booster, and fresh fluid.
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Yes I did that all simultaneous..... It holds "3rd" gear a lot longer.
Good you should not have any issues with yah tranny then. Prodigy controllers are awesome.
I also run a tranny cooler with an auxiliary fan for good measure...at the very front of the rad...

Post pics...!!!!
For the record, with a little tweaking (or maybe a lot) the TBI will blow the doors of any Vortec 350 or any 5.3 without sacrificing any fuel mileage or driveability.
Yea the sad thing is your tbi makes more hp and torque than my 2006 6.0 in my truck. 6.0s do have a lot of potential though.
Part of the low economy problem with late model engines isn't the fault of the engine at all. It's the fault of the EPA forcing emissions levels so low that in order to meet them the OE's actually have to put in enough extra fuel to fully combust the engine's by-products in the catalytic converter. Like with these occasionally fire-spewing late model diesels needing to do the same thing for the same reason.

My approach to re-gearing my engine swap was to look at what RPM's the donor vehicle's tire size and axle ratio produced at 65, 70, and 75 MPH. Then I substituted my chosen tire size and worked backwards to find a ratio that most closely gave the same RPM's at those speeds.
to get to a reasonable relationship between tire size and R&P ratio it appears to me that:

4.11 gears with 33 tires
4.88 gears with 35 tires

I know automatics benefit from the torque converter a great deal so 4.56 might be a good ratio with 35 tires.
With a calc it seems like a 2wd suburban going from 28.7 inch tires to 35s would require 4.11, a 4wd burb with the 3.73s to start and slightly bigger tires would need somehing like 4.26 to be equivalent. I do think 4.56 would be nice for strictly towing and off road but its a little high for the highway.

At this point it seems like for the price 4.11s can't be beat. Its cheaper to add 100hp to a tbi with $250 vortec heads 300$ intake adjust fip regulator, cam and chip than go to 4.56 for me with two the availability of 62 diffs to drop in.
Yea the sad thing is your tbi makes more hp and torque than my 2006 6.0 in my truck. 6.0s do have a lot of potential though.

I would love to build a really pissed off 6.0. The basic architecture of the motor will support a ridiculous amount of power. Supercharging comes to mind. Maybe one of my kids will get insanely rich and give me the funds for that. :)
Yea just a little work and there 450hp NA . I would turbo it if it was me though, doesn't make the bad mileage worse and is a little easier on the motor. That motor will handle 550 hp to the rear wheel for 100k miles. A guy here in AZ was selling a kit for 2800$ that did just that and was bolt on with the tune. In my truck though I really just didn't need it.

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