Gear ratio help, FJ60......

[KennyNole]

Have a 1982 FJ 60, currently on 35' tires with 488 front and back gear ratio's (running super high RPMs). I would like to swap out, at least the rear, for better fuel economy. I guess my questions are as follows..
1. What gears do you guys feel would be best to make this an every day driver on flat land, with some interstate use)?
2. Where should I look for the parts?
3. How difficult is this going to be?
4. Is there an after market for my 488 gears?

 

[doug720]

First, you need to change both front and rear at the same time, or never use 4 wheel drive.

Option is increase tire size, as this has the same affect as lower rpms at speed.

Gears can be expensive to buy and install. Option is to buy used 60 axles - 3:70's, or 62 axles - 4:10's

35" tires with 4:10's would be a good highway option.

 

[kling-on]

I have 456's with 35 with both my 2F and V8 love em... too bad your not closer I have some 4.10 drop out' (in a truck) I'd trade you for the 488's

 

[PortFJ62]

Seems a shame to spend the money on swapping those out but I believe that 4:56 would work or just go back to 4:11's.
Contact Just Differentials or Nitro Gear.
You probably will need a shop to set those up unless you want to pull the front end apart and rear axles.

 

[cruisermatt]

I'm in Orlando and might be willing to trade you my 4.11's... have to run some numbers through a calculator though.

 

[KennyNole]

First, you need to change both front and rear at the same time, or never use 4 wheel drive.

Option is increase tire size, as this has the same affect as lower rpms at speed.

Gears can be expensive to buy and install. Option is to buy used 60 axles - 3:70's, or 62 axles - 4:10's

35" tires with 4:10's would be a good highway option.

I'm in Orlando and might be willing to trade you my 4.11's... have to run some numbers through a calculator though.

Sounds good, let me know

 

[KennyNole]

Sounds good, let me know

Doug, sorry, posted wrong response in wrong comment. Thank you for your help

 

[bhk]

35"/4:56 will give you effective gearing that's comparable to the stock setup of 28"/3:70.

35"/4:11 will give you effective gearing that's comparable to stock gearing and 32" tires (what I have now). With the H42, it's a sluggish combo in the mountains but should be fine on flat highway.

 

[Cruiserdrew]

I would go a different way and leave what you have alone.4.88/35 is about right. What you need is a 5 speed. That will give you much better gearing overall, and by the time you trade to 4.56 gears in this one, you'd be half way to an H55f brand new.

So it's more money but much better. Anything you do is going to be expensive, so either live with it (what I recommend), or if you want highway gearing, run a different transmission.

 

[SteveH]

A 5 speed would be a cool fix for this.

Are your current gears too low for highway use? What RPM do you see at 60 mph? (you might need a GPS to accurately measure 60 mph, unless your speedometer has been corrected.

 

[Elbert]

yes...what transmission is in play is key or can be depending on your view. If you have stock 4 speed manual and you don't want to change that then you have a delima. The other question is ....is the engine stock? because if you have the stock engine and stock manual 4 speed, I don't think you can decrease your R&P gear set numerically and still have much effective torque running 35's. If you have stock engine and stock transmission and you don't want to change any of that...then it seems 4.56 would be a reasonable choice, while otherwise nothing else changes. 2f just not a powerhouse to push larger tires without gear set mods and of curse if transmission is stock you only have a 4 speeds.

what is rpm range on the hwy now...at say 65mph?

 

[KennyNole]

yes...what transmission is in play is key or can be depending on your view. If you have stock 4 speed manual and you don't want to change that then you have a delima. The other question is ....is the engine stock? because if you have the stock engine and stock manual 4 speed, I don't think you can decrease your R&P gear set numerically and still have much effective torque running 35's. If you have stock engine and stock transmission and you don't want to change any of that...then it seems 4.56 would be a reasonable choice, while otherwise nothing else changes. 2f just not a powerhouse to push larger tires without gear set mods and of curse if transmission is stock you only have a 4 speeds.

what is rpm range on the hwy now...at say 65mph?

it is a stock 2f. The rpm guage is not working currently, but I am estimating 3500+ at 65. Feels like it wants to shift at around 45mph

 

[too tall]

I would be hesitant to trade your 4.88's for 4.11's . 4.11's Are a factory ratio and they are relatively easy to find. Not the case with your 4.88's . I would be more inclined to sell the 4.88's and buy a set of 4.11's. It should be cheaper for you. Everyone has an opinion, I like to drive with traffic on the highway. 4.11's would probably be the most affordable way to go. If price wasn't a concern, I would go with an h55 and 4.56's. I do have a turboed/intercooled bj60 with 4.88's and an h55 but I run 37's. The power is slightly less than a 2f.

 

[Cruiserdrew]

The real problem with the 35 inch tires and 4.11 gearing and the stock H42 transmission is the first gear is too high. It makes it a pain to get going at a light and if there is even a hint of uphill, it's that much worse. Once rolling 4.11 and 35 will be ok on the highway, but you will find you have to shift to 3rd or even second with the slightest hill.

Bottom line, your gears are not your problem. Your transmission is the problem.

Another way to solve this same problem is to get an H41 transmission. Same dimensions as the normal USA H42, but with a nearly 5:1 low gear. Then you could consider 4.11s to take advantage of the rubber overdrive. But then you're swapping transmission and gears, which is a big project. Do it right and do it once. An H55f 5 speed is the right way to set things right, and gives you a much more driver friendly truck.