I think I Need Higher Gears w/o Changing Ring and Pinion.

[cruisermatt]

as others have said get some good numbers on your ratios and RPMs. If you still really think its an issue another option that is only slightly cheaper then a 5 speed transmission is a split-case with a 4:1 gear kit also gives you 10% under-drive in high range. I have a core I can build/machine for you if interested.

Underdrive high-range would be lower gearing, not taller like he asked about.

 

[cruisermatt]

I put a R2.8, H55 with split transfer case that has a 3:1 low range in my 78 FJ40. I also have 4:11 gears. According to Cummins with 35" tires at 80 mph I should be turning 2650 rpms.
It is not road ready so can not verify if that is correct. With the 2F and 4 speed it was wound pretty tight starting at 55 but would top out at 80 mph.

You don’t need to drive it to “verify” this. It’s just math.

 

[TheBussman]

Underdrive high-range would be lower gearing, not taller like he asked about.

sorry thinking backwards for a second.

 

[POPO AGIE]

You don’t need to drive it to “verify” this. It’s just math.

You are correct but I make a living looking and measurements and doing the math. Trust but verify.

 

[archie73]

Pretty much everything in Wyoming is few and far between. But there *might* be a few Cruiser enthusiasts or even some sort of off road vehicle club in your area. Even if they are not actual experts... they will physically be in the same place as you and your rig. Big plus. especially if you can buy them beer, mow their lawn of something to give them motivation.

I’m not in Wy, but I’m just over the boarder East Idaho. If you’re close shoot me a DM

 

[sogncab]

You are correct but I make a living looking and measurements and doing the math. Trust but verify.

Agreed. Adding the Cummins gearing calculator was within 20rpm for my vehicle because as Matt said, it's just math.

A 1% error can come from anywhere. Tire pressure, tach accuracy, speedometer accuracy.

But we're not talking 1% here. Something is off and my guess is a tach. But.... 5k on what is likely a tired old engine is likely ripping and should be identifiable by ear.