View Full Version : 15+ MPG in a Rock Stock '74 FJ40
06-08-2013, 09:17 PM
I did it! When I got my truck I was getting 11 mpg. After getting it thoroughly dialed in (including and primarily due to jetting to the nines with a wideband), my last half dozen tanks have averaged just over 15 mpg. There are a few simple things I could do that would net me a few more including:
-fix the grindy input shaft bearing in my 3-speed transmission OR
-install a decent 4-speed transmission
-remove the air pump setup (reduced losses)
-intake (not sure if there's anything out there for this)/exhaust header
-install a vacuum advance distributor
-33" tires might help a bit, but they might hurt as well
All of these require a budget that I don't currently have, but I think 15 mpg is pretty good for an otherwise rock stock 40. Ultimately this truck will get a diesel, but I'm going to continue having fun tuning this thing as far as it can be tuned in the meantime. I honestly think 18 mpg may be in the cards.
06-08-2013, 10:52 PM
Once I get my 40 back on the road and make sure my just rebuilt transmission is good to go, you can have my old H-42 four speed one if you want. One of the bearings was just starting to make a little noise, but otherwise it ran fine. You might be able to swap out the bearing without going inside, depending on which bearing it is. I might even have a good used bearing that would work. How's that for a "decent" (but not perfect) 4-speed transmission? And it fits in your current budget!
06-09-2013, 02:58 PM
I found the electric dizzy from a 60 series and 35" tires netted me the biggest gains in MPG. I can get an honest 17mpg when things are really dialed in. 15mpg is more the norm. Great job, I bet a 4 speed will really help you enjoy the rig more.
06-09-2013, 03:12 PM
I may be wrong (I haven't been able to do the research yet), but I think the H42 is the tranny out of a 60-series, is that correct? When I do the diesel swap I'll be installing a NV4500 (low low first, high high 5th). The '74 (mine's early enough to still have a 3-speed) was the first year for a 4-speed, and I'm pretty sure there's one that will more or less bolt in with the proper bell housing. Shortly after I get funding for my company, I'm hoping to track down a bolt-in set up so I don't have to do a bunch of mods to the frame that will be redone in just a year or so. I really appreciate the offer though!
The 60-series distributors, I've been told, are the vacuum advance ones that will net me additional fuel savings. I ultimately intend to track down and install some 3.70 third members (mostly for the diesel) to go with the 33" tires which will counter the speedometer deviation of the tires and make it correct again while also lowering the gearing to a more appropriate range to take advantage of the diesel's extra torque. The 33" tires combined with the 3.70 R&P will be very similar to 35" tires with a 4.10 R&P. What engine (etc.) are you running that gets you 17mpg with the 25" tires?
Additionally, thinking back on the transmission piece, the 4 speed is almost a three speed with a lower first tacked below (second and third are shifted a little to even things out, but not too much), so it might be possible that the 1.5F in there currently would be able to make better use of the gearing as well...
06-09-2013, 03:28 PM
You are both correct and not correct. The H42 is the standard 4 speed and was used in both the 40 and the 60. In the later years of the 60 it got longer so that it was the same length as a 5 speed, but the one I have is the short one for a 40. I have one of each but I am only offering you for free the one that I just took out of my 40.
I also have a set complete of 3.73 diffs ready to drop in, but they would not be free, and they would not be available until after I sell my 60 so that I know I will never need them again. Down the road, when you have funds, we could talk about those.
But for now, the tranny is yours if you decide you want it. You would need to find a bell housing that would work as the 3 speed one does not match up. Wow, its a lot of work trying to give something away. I had to pay for a rebuildable transmission.
06-09-2013, 03:37 PM
Haha! I recently gave a 60-series 4-speed to Ige. They were pretty excited about it! A "FREE" ad in the classifieds had it gone in just a few days.
I definitely still have a lot to learn with the Land Cruisers.... If I can track down that bell housing for the same price, it would very likely be a winner (any idea which bearing is grindy?)! Those diffs sound like they might have my name written on them though! They're not very desirable on the whole from what I can tell (everyone with them wants the lower gearing), but it seems they tend to be just thrown out as a result making them less than a cinch to find. I would need new drive shafts to run them at the moment (also out of budget), but I'll gladly pay for them when the time comes.
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