For a 5 speed conversion? I believe the reasons would be that it allows for a higher top speed and provides a lower first gear.
"Other rig". No Land Cruiser gets 28 mpg, especially a 40!
MPG difference with 2F engine between 4 speed and h55f 5 speed (1 Viewer)
- Thread starter cvan1971man
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
mattressking
10 digits to freedom
No, don't assume the transmission will improve fuel economy. It's only better for driveability and reduction of rpm at freeway speeds. Note that it is essentially an overdrive, you don't have much oomph in 5th.
Great for folks on the freeway, otherwise the lower 1st is nice on-trail. I think one should weigh the true benefits as many times the H55 isn't needed for many. H42 with 33s (and 35s) is decent tradeoff. I love(d) mine cruising on the interstate very long distance (10+ hour stretches)....but I've done those same stretches with H42 and it did just fine.
Great for folks on the freeway, otherwise the lower 1st is nice on-trail. I think one should weigh the true benefits as many times the H55 isn't needed for many. H42 with 33s (and 35s) is decent tradeoff. I love(d) mine cruising on the interstate very long distance (10+ hour stretches)....but I've done those same stretches with H42 and it did just fine.
Last edited:
- Thread starter
- #23
Right forgot about the 2.8. Was thinking you had a magical 2F
The other rig is a 2.4L 4-cylinder.
With 31" tires, 3.70 gears and a H55, the gearing calculator says I'm at 2050rpm in 5th gear at 60mph. Which sounds close enough to reality
My 2F was anemic at best, I'd get 11-13mpg typically.
With the Chinese cummins I get between 20-21 no matter how I drive.
.
A 40 series is a lost cause for milage. You're just plowing through the air.
My 2F was anemic at best, I'd get 11-13mpg typically.
With the Chinese cummins I get between 20-21 no matter how I drive.
.
A 40 series is a lost cause for milage. You're just plowing through the air.
- Thread starter
- #26
Hold on a second... Chinese Cummins???
Mark W
Yep, I really don't really care that much I guess.
As mentioned earlier in the responses, lugging too low while cruising will drop you below the efficiency range of the engine and eliminate any fuel savings. BUT... since the stock engine makes peak torque at 1800 rpm, you'd be hard pressed to be keeping your rpm below that on the highway. Unless maybe you were just taking a nap on the shoulder? 
The biggest fuel mileage gain I have personally seen was with a customer years ago who drove like an old lady and was meticulous about logging his fuel fills/mileage and everything else. After a "power build" which included a compression bump, headers, intake and small 4bbl carb AND most importantly a longer duration/higher lift camshaft, he saw his highway fuel consumption for his (stock geared on stock tires FJ60) drop from 13mpg to just over 16mpg. A 25% gain!
I attribute that primarily to the change in camshaft. The factory camshaft is well beyond it's efficiency range when cruising at North American highway speeds. The camshaft bumped the efficiency range upward into a more appropriate area for how the rigs gets used here. Mr Toyoda and friends expected the old F engines to spend their lives creeping around back roads, fields and village streets in the third world, not running down multilane highways in the US. To the best of my knowledge they never changed the camshaft specs over the years. If they did it was still not enough.
To your original question... around town You will almost certainly not see any improvement. For pure highway runs if you drive gentle, just relaxing in the right hand lane, I would hopefully expect to see about 10% or so gains in the long term. In flat country. In the hills and mountains, all bets are off. If you push the rig in terms of speed/acceleration/"sportiness", you will never see any difference with the 5 speed.
Mark...
The biggest fuel mileage gain I have personally seen was with a customer years ago who drove like an old lady and was meticulous about logging his fuel fills/mileage and everything else. After a "power build" which included a compression bump, headers, intake and small 4bbl carb AND most importantly a longer duration/higher lift camshaft, he saw his highway fuel consumption for his (stock geared on stock tires FJ60) drop from 13mpg to just over 16mpg. A 25% gain!
I attribute that primarily to the change in camshaft. The factory camshaft is well beyond it's efficiency range when cruising at North American highway speeds. The camshaft bumped the efficiency range upward into a more appropriate area for how the rigs gets used here. Mr Toyoda and friends expected the old F engines to spend their lives creeping around back roads, fields and village streets in the third world, not running down multilane highways in the US. To the best of my knowledge they never changed the camshaft specs over the years. If they did it was still not enough.
To your original question... around town You will almost certainly not see any improvement. For pure highway runs if you drive gentle, just relaxing in the right hand lane, I would hopefully expect to see about 10% or so gains in the long term. In flat country. In the hills and mountains, all bets are off. If you push the rig in terms of speed/acceleration/"sportiness", you will never see any difference with the 5 speed.
Mark...
Last edited:
POPO AGIE
SILVER Star
I did along time ago and replaced with a 155F that free.
POPO AGIE
SILVER Star
The blocks are made and bored in China then sent to Indiana and finished machining and assembly. They install service sleeves so it is not the same 2.8 sold in the Asian market. The 4bt, 5.9 or 6.7 do not have service sleeves. The 2.8 was used in F250s in Latin America.
Check out the Ultimate Adventure videos they had several rigs powered by the R2.8 and no failures. Look up Dirt Every day video where Fred installed the R2.8 in his Tube Sock jeep and drove under water twice. Big tire garage has a square back Wagoneer with wrangler front clip that has video in Moab.
Last edited:
Consensus appears to be that an FJ40 is not an economy vehicle. As for cool, it’s over the top
Breadbox on wheels!
16 mpg once or twice at 60 - 65 mph with fuel injected vortec 350 in front of an NV4500 and narrow 33" Toyo M-55s. 1975 4.11s
Usually 13-14, and 12 mpg in town.
- Thread starter
- #34
My son is driving it back and forth from college in Central Texas and it's quite flat. The highest thing we have here is an overpassAs mentioned earlier in the responses, lugging to low while cruising will drop you below the efficiency range of the engine and eliminate an furl savings. BUT... since the stock engine makes peak torque at 1800 rpm, you'd be hard pressed to be keeping your rpm below that on the highway. Unless maybe you were just taking a nap on the shoulder?
The biggest fuel mileage gain I have personally seen was years ago with a customer years ago who drove like an old lady and was meticulous about logging his fuel fills/mileage and everything else. After "power build" which included a compression bump, headers, intake and small 4bbl carb AND most importantly a longer duration/higher lift camshaft, he saw his highway fuel consumption for his (stock geared on stock tires FJ60) drop from 13mpg to just over 16mpg. A 25% gain!
I attribute that primarily to the change in camshaft. The factory camshaft is well beyond it's efficiency range when cruising at North American highway speeds. The camshaft bumped the efficiency range upward into a more appropriate area for how the rigs gets used here. Mr Toyoda and friends expected the old F engines to spend their lives creeping around backroads, fields and village streets in the third world, not running down multilane highways in the US. To the best of my knowledge they never changed the camshaft specs over the years. if they did it was still not enough.
To your original question... around town You will almost certainly not see any improvement. For pure highway runs if you drive gentle, just relaxing in the right hand lane, I would hopefully expect to see about 10% or so gains in the long term. In flat country. In the hills and mountains, all bets are off. If you push the rig in terms of speed/acceleration/"sportiness", you will never see any difference with the 5 speed.
Mark...
brian
SILVER Star
Best I've seen was 16 after a head rebuild.
14 is the norm.
14 is the norm.
- Thread starter
- #36
4 cyl diesel?
Cummins R2.8. I call it the ChiCommins
Dual-spark ignited gasoline 4 cylinder, Datsun / Nissan Z24 with a 32/36 Weber. Any of the efficiency that I observed is likely because I'm making more NOx, as the factory set-up used retarded spark timing to make gains with the exhaust. My O2-sensor suggests that I'm really lean when I'm running EGR, like beyond the gauge-range. I'm lazy and I run the engine with vacuum controls instead of the computer, as I can't figure out how to fix the computer-controlled carb with enrichment solenoid.
The thing that I like about my Datsun is it has a 5-speed, and it has awesome compression-braking. The 40 with 4.11s, 215/75/R15s, H42 is essentially slowing down with the brake pedal, combined with some down-shifting, but, I can really dial-in the Datsun without using friction brakes, as the brakes get hot (smoke), driving at altitude in the mountains.
Knowing what I know now, I'd go another direction. It's fine. But it wouldn't be my first choice.
FJBen
SILVER Star
Even diesels won’t give you much of an economy bump. They are just tractors with awful aerodynamics and like to rev low. You will never see mpg money back on a 5spd swap and for sure never on a diesel swap u less you get the stuff very very cheap.
I’ve got a 1988 BJ74, (like a “modern” FJ40) 4cyl turbo diesel, H55f and I’ve averaged 20mpg for over 5 years of tracking and 60k miles. Best almost all highway was 24mpg. That’s city/hwy winter summer etc. most of the time it’s 44-60mph and back roads. That’s 6-8mpg better than a 40 on average with the added cost of diesel.
Cheapest way to improve your mpg? Buy a Corolla
.
I’ve got a 1988 BJ74, (like a “modern” FJ40) 4cyl turbo diesel, H55f and I’ve averaged 20mpg for over 5 years of tracking and 60k miles. Best almost all highway was 24mpg. That’s city/hwy winter summer etc. most of the time it’s 44-60mph and back roads. That’s 6-8mpg better than a 40 on average with the added cost of diesel.
Cheapest way to improve your mpg? Buy a Corolla
.Similar threads
