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40" tires with 4.88 gears on fullsize chevy???

K

K20Chevrolet

1/2 ton status
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Feb 1, 2013
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Pittsfield, ME
Hi everyone,

my new axles have 4.88 gears and I´m in for some new tires. Initially I was thinking 37", hence the 4.88 gears. I´m now also concidering 40" tires but I´m unsure that the 4.88 will work ok with the 40´s. They might be too tall...

I also have to say I ahve a V8 with around 500HP and a 6 speed manaul with overdrive.

Does anybody have any experience with 4.88 and 40s? Any info will be helpful, Thanks!
 
TheBeast_88K5 said:
I think at 500 horse, it don't matter much....
Click to expand...


Well, it is not the power I´m concerned about, more the stress on everything drivetrain wise and somewhat about the performance/millage thing. It is used as a street driven truck that is also the offroad toy for the weekends. So it needs to still work on the street and really shine offroad. I know the 4.88s are great with the 37" tires...
 
I used to run that setup on my 3/4 ton. I had a SM465 W/ a mildly built 350. Ran great on the highway.
 
I have 37'' BFG MT with my 4.88 gears and 350/350 combo, no overdrive :(. I cannot go much faster than about 60MPH, but you having overdrive likely would be just fine having any 37-40'' tire you wanted.
 
fallguy said:
I used to run that setup on my 3/4 ton. I had a SM465 W/ a mildly built 350. Ran great on the highway.
Click to expand...

was it OK offroad too, or a little tall??

2BLAZERS said:
I have 37'' BFG MT with my 4.88 gears and 350/350 combo, no overdrive :(. I cannot go much faster than about 60MPH, but you having overdrive likely would be just fine having any 37-40'' tire you wanted.
Click to expand...

that is what I originally planned, 4.88s and 37"... but as things go you can always go bigger, so I thought about 40´s but won´t regear the brand new axles. So if 40´s work, great, if they don´t I´ll stick with 37´s.

Thanks for your input!
 
What RPM is the torque peak at?

The closer you are to that value at your preferred highway speed, the better.



-G
 
I think it will be fine and definitely not a big enough difference to spend the time and money to do another set of gears. People put too much emphasis on axle gears and the difference between minor changes. You already have 4.88, so assuming you have a 14FF rear the lowest you can go is 5.38 and it's not that big of a difference.

I will also say that axle gearing should primarily be used to optimize the pavement performance (i.e. 2wd high range). Low range in the transfer case gives you the gearing for off-road performance and makes a much bigger difference than anything you could ever do with axle gears. In my years of trailriding I have never seen anybody get stopped at an obstacle and say "if I only had 5.13 gears instead of 4.88 I would have made it". My last statement is I have a friend that has wheeled hard for years in a truck with 4.10 gears and 42" tires, along with a C6/205 combo, that provides a very "poor on paper" crawl ratio but it does good. It has a big-block but it's down in the 350 HP range and has plenty of power.
 
4.88 gears will be fine with 40s.

And as was said above if you are worried about off road performance than some sort of transfer case mods will do substantially more than going from 4.88s to 5.38s. Its only a 10% change.

Shoot I ran 42s with 4.56s no overdrive and a stock motor and my rig was perfectly fine at 70 mph
 
As said I have a setup like that
39.5" tsl's on 4.88s with a th400. I cruise comfortably at 60-70. And without making thins obnoxious can get up around 75. But after that it starts getting a bit much. But it's more vibration of unbalanced bias plys than the engine running out of juice
My engine is just a stock gm crate 350 with an undisclosed amount of miles on it.

As far as on road I have no problems. I can spin em no sweat and put it in 4 low and it crawls decent enough. I'm sure with more power you'll have no problems.
Plus you have way better gear spread than my 3 speed.
I have a semi float 14 bolt out back and a Dana 60 and so far offroad I've not damaged anything. But I've only done some mild wheeling this far
 
Deuling said:
Smokinthehippies here has that setup
Click to expand...

Thanks for the info...

Greg72 said:
What RPM is the torque peak at?


The closer you are to that value at your preferred highway speed, the better.


-G
Click to expand...

With minor ups and downs I pretty ,uch have 99% of the peak torque from 3500 to 4500 RPM

6.2Blazer said:
I think it will be fine and definitely not a big enough difference to spend the time and money to do another set of gears. People put too much emphasis on axle gears and the difference between minor changes. You already have 4.88, so assuming you have a 14FF rear the lowest you can go is 5.38 and it's not that big of a difference.

I will also say that axle gearing should primarily be used to optimize the pavement performance (i.e. 2wd high range). Low range in the transfer case gives you the gearing for off-road performance and makes a much bigger difference than anything you could ever do with axle gears. In my years of trailriding I have never seen anybody get stopped at an obstacle and say "if I only had 5.13 gears instead of 4.88 I would have made it". My last statement is I have a friend that has wheeled hard for years in a truck with 4.10 gears and 42" tires, along with a C6/205 combo, that provides a very "poor on paper" crawl ratio but it does good. It has a big-block but it's down in the 350 HP range and has plenty of power.
Click to expand...

Thanks, well I do have a 4.3 Atlas II, so my low range is quite low enough I would say. Plus the first gear in the 6 speed is 5.8:1 roughly...and I have a 14FF

blazinzuk said:
4.88 gears will be fine with 40s.

And as was said above if you are worried about off road performance than some sort of transfer case mods will do substantially more than going from 4.88s to 5.38s. Its only a 10% change.

Shoot I ran 42s with 4.56s no overdrive and a stock motor and my rig was perfectly fine at 70 mph
Click to expand...

Smokinthehippies said:
As said I have a setup like that
39.5" tsl's on 4.88s with a th400. I cruise comfortably at 60-70. And without making thins obnoxious can get up around 75. But after that it starts getting a bit much. But it's more vibration of unbalanced bias plys than the engine running out of juice
My engine is just a stock gm crate 350 with an undisclosed amount of miles on it.

As far as on road I have no problems. I can spin em no sweat and put it in 4 low and it crawls decent enough. I'm sure with more power you'll have no problems.
Plus you have way better gear spread than my 3 speed.
I have a semi float 14 bolt out back and a Dana 60 and so far offroad I've not damaged anything. But I've only done some mild wheeling this far
Click to expand...

Thanks for all the info..this was helpful! I do have a 14FF and D60 up front. So after hearing all of this, I guess I should be fine with 40´s on my set up. Thanks guys!
 
I think the only weak link you're gonna find is ujoints and the locking hubs up front. But if you drive smart it'll be good stuff
 
The 1410's will be fine but the Warn hubs are known to be weak.
 
one question I might ask first is, do I really need the 40´s or are 37´s large enough....

Truck is still street legal, needs to pass inspection, it is used on the street, used to tow and haul stuff and also serves as a weekend offroad fun toy. So it kind of needs to do everything well....
 
The Dynatrac's are stronger in both material and design. They are a copy of the Spicer hub design.
 
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