Changing Tires 38.5" to 44"... How Much Effect?

[krek]

I bought my truck used, I have no idea of the gear ratios. All things being equal, if I switch from a 38.5 inch tall tire to a 44 inch tall tire... how much is this going to affect acceleration, etc?

[never_2_high]

alot your going to need to put a bigger and what i mean by bigger is a low gear like a 4.56 or some thing of that effect what are you trying to use the truck for if you just looking for the get up power you could go all the way to a 6.17 gear but if you want top speed your going to need a way smaller gear like a 4.10 or 4.56

[BRUTUS]

Think of it this way... doing that switch... the 44" tire travels 17.25" further per revolution than the 38.5" tire. Speed comes at the expense of torque. And you are talking about a 14% increase in speed so that would correspond to a 14% decrease in torque. I am putting 4.56" in my truck for 38.5" tires and I consider them to be "fast" gears for a 38.5" tire.

Depending on what you want from your truck... read through this chart and determine what gears you want. It is pretty self explanatory.

http://www.4lo.com/calc/geartable.htm

[krek]

That chart is fantastic, thanks!

This truck is used exclusively for mud pits... what gets one through a pit? Speed? Torque? Skill? Luck?

[BRUTUS]

Mud = Speed... momentum etc. Torque is only needed to get the tires up to speed... hopefully the tires are self cleaning (fun to watch).

Have you run the J10 yet? Doesn't it run on methanol or something SBC? What are your impressions of it at this point? Are you going to leave the cab brow-castrated? Have you taken it boggin' yet? Get some video to post ASAP!

[krek]

The engine seems to like pump gas just fine. I bought some 115 octane unleaded just to be safe and we're going to try it out on Saturday at a nearby "4x4 farm". (www.bricks4x4farm.com)

I'll have photos and video afterward.

The little bit I've driven it around our property (and one excursion down the road) have told me:
1. It seems to have a relatively high stall converter in it.
2. It had a HUGE turning radius with the front hubs unlocked.
3. It's worse with the front hubs locked.
4. The engine seems pretty strong.

[BRUTUS]

That is definately a mudder... high stall converter would be fun in the mud.

There isn't much turning in the mud anyways.

Strong small block chevy... just like the ad said...

DEFINATELY A MUDDER!

[robselina]

What axles do you have in that thing?

You'll want to find that out 'cause even if someone swapped in a D60/GM14FF combo you're pushing your luck with 44" tires....

[krek]

I think I have a Dana 44HD front and Dana 60 rear. Everyone who looks at them has a different opinion.

That's a good point on the 44s. The trade is off anyway as the 44s were considerably more worn than advertised.

[Brad W.]

look for a number cast on the housing near the pinion or one of the gusset ribs. there will be a 44 or 60 cast into it. The dana 60 looks like the 44 except its much larger.

[Stuka]

The diameter of the tire isnt the only thing, its also the mass difference. A 44" tire which is generaly 19.50 wide is going to weigh a whole lot more than a 38x12.0 or 38.14.50 tire. Your engine has to deal with that rotational mass. So generally when going up in tire size to keep the same accelleration feeling you go one step farther for gearing.

[maximum destruction]

look for a number cast on the housing near the pinion or one of the gusset ribs. there will be a 44 or 60 cast into it. The dana 60 looks like the 44 except its much larger.

HI KREK. what BRADW mentioned is the correct way to identify what axle u have. the only problem is that dana axles are the only axles that use this method of identification. depending on the year of the chevy chassis, u may have a corporate 10 bolt front which won't have any markings. the easiest way for me to identify an axle is simply look to see if it uses ball joints or kingpins at the knuckles. kingpins & u have a 60. balljoints & u have either a dana 44 or a 10 bolt. neither of the 1/2 fronts will live long under 44s & hard use. the secret to keeping a 60 alive is not to raise he77 on it with the wheels turned. the axle joints are the weakest link.