need another gear!!!

[Banger88]

Was wondering if i could upgrade gearbox in my fj40 currently running standard 2f with four speed box, but it whines too much and too much rpm when on highway. what gearbox (5 speed) could bolt straight on? or is there other alternatives out there?

 

[Rainman]

I ran an NV4500 5 speed in my Zebranator but it's no direct bolt in. Sure gave me a great low 1st and high 5th. And I'd swear you could leave a wrench in the thing and it would eat it for lunch without a hitch.

Sorry... That wasn't much help was it?

 

[SouthBostonFJ40]

The 3 speed and the 4 speed have the same top gear ratio.

 

[brian]

3:70 rears and 33's.

 

[Banger88]

brian, when u say 3:70 rears, do you mean diff? if yes what diff would work

 

[Banger88]

I ran an NV4500 5 speed in my Zebranator but it's no direct bolt in. Sure gave me a great low 1st and high 5th. And I'd swear you could leave a wrench in the thing and it would eat it for lunch without a hitch.

Sorry... That wasn't much help was it?

hey thanks NV4500 WOULD come out of what vehicle?? chevy, gmc van? where would i get conversion kit

 

[shawnfj40]

Brian is right. If you want something that is bolt in without modifying anything change your differential gears and if your 4 speed is still whining rebuild or replace it. for a 33 or 31 inch tire a 3.70 gear is a good choice to keep decent manners on and off road.

 

[jim land]

-h55 and split case = bolt on but you lose the TC parking brake , need a crossmember and driveshaft mod
-nv4500 = adapter for stock TC , custom support-crossmember , driveshaft mod and maybe bellhousing and clutch
-3;70 or taller tire = super simple

 

[1911]

...when u say 3:70 rears, do you mean diff? if yes what diff would work

Yes; third members from a late ('79-on) 40 would drop right in. You'd want to do both front and rear of course.

 

[65swb45]

3:70 gearing is a very viable option. To find out if this will satisfy you BEFORE spending the time, energy and $$, you should try and borrow a set of tires that are approximately ten percent bigger than what you have. This will approximate both the engine RPM reduction and the increased drag of the taller gears.

Best

Mark

 

[Chungas Revenge]

Ditto on the 3.70 gear swap. I made the same decision for my 76 TLC as a hunting/bush rig. Made the swap due to the same issues I assume you are debating. At the same time I went w/taller tires on 17" rims from a late model FJC, "Marks Header" (Thanks Mark) and Plug-in electronics in order to round out my highway performance without sacrificing my trail capability. Running down a set of new 3.70 took some scrounging. But again, for my particular set of "Decision Criteria" and intended use (Read: $$+Time+ease of effort=perfect hunting rig/non invasive mod) this was IMHO a good option. W/this combo I can sustain reasonable highway speeds (65 with a good tail wind), while packed for extended trips and still climb in and out of the hunting trails. Saw a slight increase in gas mileage as well. Overall a good option for you to consider....

 

[Mace]

Swapping your 4.11 diffs for a set of 3.70 gears out of a later 40 or 60 series should be easy with as many people who want to go to a higher numerical ratio to make up for larger tires.

 

[Chungas Revenge]

I boosted the chart from the following:

https://forum.ih8mud.com/threads/fo...h-gear-size-to-use.826450/page-2#post-9489278

Good cross reference for trans/gearing/rpm/mph

 

[handcannon]

That chart that Chungas posted is interesting and appears to be quite useful (don't recall seeing it previously). But, if you want to do more playing around with gear and tire combinations check this out.

http://www.grimmjeeper.com/gears.html

Don

 

[Living in the Past]

Switching the whole diff would be the easiest option as they were used here from the 79 model thru the 87 model and fairly easy to find. OP list location as Jamaica and that may not be the case. The 3.70 gears seem to be North American gearing for gas mileage and most the rest of the world continued with 4.10 gears. Which way to go might depend on what was imported to that market. Might have 60 series with H55F five speeds and later 4X series rear axles with the hand brake.

 

[Banger88]

hey guys, thanks for input The vehicle was, the body at least is a diesel bj42 , i replaced (changing mounts) to 2F petrol. so what ratio would the diffs be ? i think the vehicle was a 1980-82?

i do however have a set of diffs from a fj40 circa 1975-8 . which would be my best bet for motorway?

 

[Chungas Revenge]

so what ratio would the diffs be

2 cents worth... If its not stamped or tagged on the housing, remove the differential cover and count the number of teeth on the gears. Count the number of teeth on the ring gear and the pinion gear. Divide the number of ring gear teeth by the number of pinion gear teeth. That number is your gear ratio.

There are several "you-Tube" vids that demonstrate a non invasive method as well. But IMHO, If you are going to swap out the diffs, I would open them up just to have a "look-see".

Good link below: http://www.crawlpedia.com/gear_tooth_calculator.htm

 

[Fast Eddy]

There are several "you-Tube" vids that demonstrate a non invasive method as well.

Jack up the rear, both tires with the tranny in neutral. Put a mark at the bottom of a tire. Crawl under and spin the driveshaft exactly four times. If the tire has not gone around quite one time, you have 4.11 gears. If it went a little more than once, you have 3.70s.

 

[Mace]

Keep in mind that both tires have to spin at the same time. If one spins faster your numbers will be off.

 

[Living in the Past]

Just leave it on the ground and roll it straight one full wheel turn. If the driveline rotates just over four times it would be 4.10 under the four turns probably 3.70.