Tire Size/Gearing

[corbinwalp]

I bought my truck with 255/85/16 mud tires and 4.75 custom pegged GBR diffs & arb air lockers, I run at 3200-3300rpm at 70mph. I know this is high, so what are my options? I need new tires anyway, do I get the same size I have now and not worry about the rpm? Or can I go a bit bigger and decrease rpm some (is this correct?). Also, if I did go larger, would gear strength, etc. become an issue?
Thanks

 

[ZG]

Go bigger tires and you'll have a lower RPM at 70. Do you have stock axle shafts? How much lift? 4.75 is really high on a D2, should be running 35s at least.

 

[corbinwalp]

Ive got tom woods driveshafts, the u-joint conversion, and a 2" lift. With the 33"s that I have now I don't have any rubbing but there isn't a lot of room either. Im thinking that I'd need spacers or a body lift to fit 35's

 

[Howski]

That's a hell of a lot of gear for 33's. I ran 33's w/o issue on my D2 with stock gearing. You could possibly go to a 1:1 transfer case (opposed to the factory 1.2:1) which would keep the excellent low range ratio and with a reduced high range for lower highway rpm. Regardless of your decision, it will probably cost you some coin in the form of 3"+ suspension to fit larger tyres, transfer case gearing or differential gearing.

 

[ZG]

4.11s is what I run on 33s, it's pretty ideal. You'll either need different gears(even 4.37s would help) or bigger tires. Or you can swap out the t-case but that might be more of an ordeal and $$$

 

[Howski]

4.11s is what I run on 33s, it's pretty ideal. You'll either need different gears(even 4.37s would help) or bigger tires. Or you can swap out the t-case but that might be more of an ordeal and $$$

Guess it really depends on the abilities of the OP. If he'll be taking it to a shop swapping diffs or swapping the t-case may be close to a wash depending on parts availability and cost for t-case gearing.

Another option is look for someone who has a set of 3rds with 4.11's who may be willing to trade or purchase those then sell yours. If you can turn a wrench this may be the easiest option.

 

[ZG]

Ahh never mind, I was thinking it'd be hard to find just the gear sets for the LT230. Thought GBR only had reduction gears, looks like Ashcroft has a great selection.

http://www.ashcroft-transmissions.co.uk/lt230-ratio-changes.html


I'd go that route.

 

[corbinwalp]

Guess it really depends on the abilities of the OP. If he'll be taking it to a shop swapping diffs or swapping the t-case may be close to a wash depending on parts availability and cost for t-case gearing.

Another option is look for someone who has a set of 3rds with 4.11's who may be willing to trade or purchase those then sell yours. If you can turn a wrench this may be the easiest option.

So 4.11 gears would be ~$500, transfer case gears set is ~225 euros, and I don't think I want to deal with a suspension lift and larger tires. I'm not too confident in my mechanical skills but which would require least skill to install?

 

[sedat]

a T case would be easier to regear.

Why run 4.75s to begin with? thats a LOT of gearing for 33s.

personally? I'd throw 35s on it and some spring spacers. You already have most of the weakspots of the axles eliminated.

Edit: Your 5.0 would turn 33s no problem on stock gears.

 

[Howski]

So 4.11 gears would be ~$500, transfer case gears set is ~225 euros, and I don't think I want to deal with a suspension lift and larger tires. I'm not too confident in my mechanical skills but which would require least skill to install?

If you're not confident in your mechanical skills at all I'd suggest having a shop do the work (differential or transfer case re-gear). If not set up correctly the new gears can cause major issues down the road. If you can find complete third members complete with 4.11 (or lower) gearing and ARB's installed this would make the task easier

 

[tacr2man]

If you go on Ashcrofts site , they have a ratio calculator that you can run different permutations on . the bigger your tyres the more stress gets put up the driveline. JMHO

 

[corbinwalp]

a T case would be easier to regear.

Why run 4.75s to begin with? thats a LOT of gearing for 33s.

personally? I'd throw 35s on it and some spring spacers. You already have most of the weakspots of the axles eliminated.

Edit: Your 5.0 would turn 33s no problem on stock gears.

Truck had 4.75 installed when I got it...otherwise I'd have put in 4.11

Do you think spacers and 35s is okay as far as extra stress?

 

[sedat]

Next weakest link is the halfshaft/c/v if they're still stock. Seeing as how the diffs already pinned with ARBs I wouldnt worry too much.

 

[Drover]

It's not just as simple as 35's and spacers. Well I guess it is if you don't care about the way it drives.
If goin 35's , and adding more lift (which you'll need) , then your castor will be off. You'll have to send you arms in to get cut and cranked. And then you'll have to go to a woods double double front shaft. Or you'll smoke the u-joints quick. This is all stuff I speak from experience.


That's 6" of lift and 35's, and it will still rub. I had to cut the rear frame mount on my arms and move it forward 1 3/4"
Or you'll have to cut your fender wells. I think cutting the fender wells is half assed , so I opted for moving forward the mounts.

There's not many guys runnin 35's on disco's correctly. A lot of roached out trail rigs , not daily drivers. I've seen your truck before, too nice to half *ss it.

Oh, and for 35's you want to be at 4.37's

 

[corbinwalp]

It's not just as simple as 35's and spacers. Well I guess it is if you don't care about the way it drives.
If goin 35's , and adding more lift (which you'll need) , then your castor will be off. You'll have to send you arms in to get cut and cranked. And then you'll have to go to a woods double double front shaft. Or you'll smoke the u-joints quick. This is all stuff I speak from experience.
View attachment 222766

That's 6" of lift and 35's, and it will still rub. I had to cut the rear frame mount on my arms and move it forward 1 3/4"
Or you'll have to cut your fender wells. I think cutting the fender wells is half assed , so I opted for moving forward the mounts.

There's not many guys runnin 35's on disco's correctly. A lot of roached out trail rigs , not daily drivers. I've seen your truck before, too nice to half *ss it.

Oh, and for 35's you want to be at 4.37's

You're right, so it looks like I'll be doing transfer case gears. What ratio is best? 1.410, 1.667, 1.222 (isn't this stock?)