I want to lower the RPM’s in my 4spd FJ62 (1 Viewer)

[Saucerman]

I know the obvious answer is a 5 speed. That can’t happen right now. Transmission and transfer already rebuilt and installed. It runs great and I am going to enjoy it. No more stupid kick down cable.
my only concern is the new RPM range. It’s much higher. I am an the 2500 range at 50mph. So my question. Is there anything else I can do to lower the RPM’s ? This truck is not a crawler, nor is it mudder. I use it to drive to the mountains and hike. It goes down dirt roads and forest service roads and of course to work every Friday. It has stock size tires and wheels.

 

[BMValentine]

I know the obvious answer is a 5 speed. That can’t happen right now. Transmission and transfer already rebuilt and installed. It runs great and I am going to enjoy it. No more stupid kick down cable.
my only concern is the new RPM range. It’s much higher. I am an the 2500 range at 50mph. So my question. Is there anything else I can do to lower the RPM’s ? This truck is not a crawler, nor is it mudder. I use it to drive to the mountains and hike. It goes down dirt roads and forest service roads and of course to work every Friday. It has stock size tires and wheels.

Re-Gear the differentials. What size tires are you running?

 

[Silveredition]

Bigger tyres - or just drive it!

 

[FJACS]

Drive slower

 

[Saucerman]

@BMValentine tires are 235/75 15.
@FJACS what a riot, can’t drive slower around here, you’ll get run over, even in a Landcruiser. Every stooge around here has an suv they are using to practice their formula 1 skills in.

 

[BMValentine]

The FJ62 diff gear ratio is 4.10 and the FJ60 is 3.70 so you could re-gear to the stock FJ60 ratio. The other option, as someone already stated, is to get bigger tires.

how does the it drive with the 4-speed manual? I’m watching my autotrans deteriorate and like you the 5-speed is priced out of my range right now.

 

[Saucerman]

It drives great with 4speed! Very responsive. You hit the gas and go. Seriously my only concern is the higher RPM’s at what for me is normal driving speeds. The auto barely got over 2k rpm’s.

 

[BMValentine]

If you could find a couple of complete FJ60 differentials on the classifieds that might be the cheapest way to get a re-gear. You may find someone who would trade or keep your current ones for spares. New tires would probably be the best second option and go up to a 33inch tire. And then lastly I would look at re-gearing as gears themselves are cheap but getting them installed is where they get a little pricey.

 

[The Phoenician]

How much cheaper is it to regear than to just save up for the 5-speed transmission?

 

[Godwin]

Swapping in 3.70 diffs from a FJ60 will lower your rpm by about 11% (if my math is correct). If that is not enough go up to a 31" or 33" tire.

 

[Seth S]

There might be someone on here looking for some 62 diffs who is willing to trade you their 60 diffs. Otherwise consider going to 33” tires and I think you will be happy.

 

[Saucerman]

Well I am saving for the 5 speed for sure, but no need to re-do all that work just yet. I may have to live with higher RPM's for a while. The easiest way is to get taller tires or taller wheels or something of that nature. I have new tires so I probably won't even be doing that. In my case it might just be the easiest and best to just enjoy as is for a while and keep her at 2500 RPM's. I don't HAVE to go 65 mph, it would just be nice.

 

[Seth S]

The jump to a 31” tire on my 3.70 diffs made a nice improvement to revs with my 4 speed. Cost about $600 for a set of 31” tires.

 

[Gretsch]

My '84 has the stock 4Speed, stock axles, and recent 33's. The RPMs on mine @70-75 are right around 2800-3100, just for some real world info of recently going to 33's. That's down from just a touch over 3000 with 30's. The 33's did lower the RPMs, but not nearly as much as many of the claims I have seen on here said it would. I had seen estimates all the way down to 2500 with 33's, which I don't see myself. That's not to say the current setup isn't completely workable. Its fine for me at the moment. Just not as improved as I thought it might have been, and I will be seeking a 5Speed in the future. HTH.

 

[OSS]

Just get 31" tires and it'll be perfect.

 

[John Staton]

sounds about right...I jumped to the H55 and now I am just over 2500, but at highways speeds. Before that I was at 3000 headed up the interstate and it drove me crazy. Felt like Scotty...."I am giving it all I got..." in a Scottish accent. Now the only time I even get close to 3000 is when I dont shift from 1st to 2nd quick enough.

 

[Godwin]

I'm set up with H55F, 4.11s, 285/55/16 (33") tires and running at 2500 rpm my speed in 5th is right about 70 mph.

 

[Dynosoar]

33" tires with 4.11 gears is the same as (really close) 235/75 15 with 3.70 gears.

 

[Saucerman]

Shoot yeah, 33's would be awesome! Truck would look real mean then. Thanks for the suggestions folks.