4.88's

[wingnut2u]

I just put on some Toyo MT's 37x13.50x18 and I need to re-gear. I pull a boat and do a fair amount of highway driving. Based on previous threads, I am assuming that I should change to the 4.88 gears. Comments or Suggestions?

Also, since there is a large contingency here from the DFW area, where is the best place to take my big yellow banana bus to have the work done?

How 'bout them Cowboys?! Romo for President!!!

[OrangeCrush]

Though I have 38's and 4.56's, I wish I had gone with 4.88's.
I would normally think 4.56's would be great with 37's but if you plan on doing any towing, I'd recommend 4.88's with the 37's.

HTH's,

Mark

[4rnRootsH2SUT]

I'm confused here. I also have 37 Toyo MT's on 24 inch wheels. I do a lot of highway driving. Would regearin' help me out as well?

[KONG]

so is it a good idea to change the front to 4.88 too?

[ASTAR]

Originally Posted by KONG

so is it a good idea to change the front to 4.88 too?

YOU MUST HAVE MATCHING GEARS FRONT AND REAR

[wingnut2u]

Another question is, if I switch to the 4:88's how will this effect my top end speeds, say around 70-75mph

[Captain of the Titanic]

(New Tire Size / Old Tire Size) - 1 = Increase in Tire Perimeter

in this case 37/35 = 5.7 % Increase in T.P. This means that your engine will turn 5.7% less (rpm) to go a certain speed, but it will have to push 5.7% harder at that rpm to cover the distance. This makes the truck sluggish and takes away from the "punch" when you hammer it. This will also take the truck out of the "sweet spot" where you get the best mileage on the highway.

Old Gear Size * Increase in Tire Perimeter = New Gear Size Needed.

In this case 4.10 * 1.057 = 4.33. This means that to get the same performance you need at least a 4.33 gear to get back to normal.

Now this is where it gets interesting. While your in there doing it... You have to think about what kind of performance you really want. The higher the gear the more "punch" you have with the accellerator. The higher the gear, the lower the top speed. And of course, you no longer operate in the "sweet spot" mentioned earlier.

Personally, if I was swiching gears, which I will do eventually, I would go with the 4.88, screw the MPG and MPH, and enjoy the "punch". Passing cars will be a breeze and offroad will be a blast.

You will, however need to get your computers reset for the change in tires and gears.

I previously did a great deal of changes to my 99 Tahoe, and it cause my ABS to no longer function. I don't believe this is a problem with the H2s though.

I would also address putting some serious lockers in as well.

If you changed to a 4.88, you would have the following change

4.88 / 4.33 = 12.7% net change in performance. If your truck ran at 2000 RPMs at 60 mph, it would run at 2234 RPMs. If the top speed was 135, it would be 119.

It would also go like a scalded dawg...