1973 FJ40 Gear Change (1 Viewer)

[cvan1971man]

Got a 1973 FJ40, and thinking about changing the gears to get more highway friendly. I believe it has 4.10's in it and after '79 they moved to 3:73 gears for fuel efficiency. . It has a '78 Motor, 4spd transmission and t-case

Has anyone done this? What is the typical cost and who is the best source for the new ring/pinion, bearings, etc. ? Is there any negatives to it? What can I expect for the all in costs?

 

[Mark Jennings]

If you’re running a 3 speed, and have a tire much more than 31 inches, you’ll have a bit more difficulty in getting her rolling from a dead stop. The 3:73 gears work much better with a 4 speed, lower first.
Some numbers to Ponder…

31 inch tires, 4:11 gears, 1:1 transmission ratio (3rd gear 3 speed, 4th gear 4 speed)…

40 MPH…1783 RPM
50 MPH…2230 RPM
60 MPH…2675 RPM
70 MPH…3121 PPM

Same set up with 3:73 gears…

40 MPH…1618 RPM
50 MPH…2023 RPM
60 MPH…2427 RPM
70 MPH…2832 RPM

 

[cvan1971man]

If you’re running a 3 speed, and have a tire much more than 31 inches, you’ll have a bit more difficulty in getting her rolling from a dead stop. The 3:73 gears work much better with a 4 speed, lower first.
Some numbers to Ponder…

31 inch tires, 4:11 gears, 1:1 transmission ratio (3rd gear 3 speed, 4th gear 4 speed)…

40 MPH…1783 RPM
50 MPH…2230 RPM
60 MPH…2675 RPM
70 MPH…3121 PPM

Same set up with 3:73 gears…

40 MPH…1618 RPM
50 MPH…2023 RPM
60 MPH…2427 RPM
70 MPH…2832 RPM

sorry, meathead moment. it is a 4 speed. It has a '78 Motor, transmission and t-case

 

[cvan1971man]

If you’re running a 3 speed, and have a tire much more than 31 inches, you’ll have a bit more difficulty in getting her rolling from a dead stop. The 3:73 gears work much better with a 4 speed, lower first.
Some numbers to Ponder…

31 inch tires, 4:11 gears, 1:1 transmission ratio (3rd gear 3 speed, 4th gear 4 speed)…

40 MPH…1783 RPM
50 MPH…2230 RPM
60 MPH…2675 RPM
70 MPH…3121 PPM

Same set up with 3:73 gears…

40 MPH…1618 RPM
50 MPH…2023 RPM
60 MPH…2427 RPM
70 MPH…2832 RPM

I don't foresee us doing a lot of wheeling in it unfortunately. But that is where things are. Do you know what kind of a job it is to swap those out? Cost, etc.?

 

[Mark Jennings]

sorry, meathead moment. it is a 4 speed. It has a '78 Motor, transmission and t-case

OK first issue solved, ‘getting her rolling from a dead stop’. However, your 4th gear ratio is still 1:1, so the above changes in RPM can be expected.

 

[Tigerstripe40]

It's doable, but the 3.73s are the most expensive gearsets.
What does 'more highway friendly' really mean to you?
You're going to have less 'giddy up go' feeling and more overall top speed, but really, 4.11s will get your truck to 65-70mph.

Also, while you are in there, you might consider adding selectable lockers, which adds value to the rig.

With that said, I feel that an H55F, while being more expensive, will give a better driving experience overall than regearing to 3.73s.

 

[cvan1971man]

It's doable, but the 3.73s are the most expensive gearsets.
What does 'more highway friendly' really mean to you?
You're going to have less 'giddy up go' feeling and more overall top speed, but really, 4.11s will get your truck to 65-70mph.

Also, while you are in there, you might consider adding selectable lockers, which adds value to the rig.

With that said, I feel that an H55F, while being more expensive, will give a better driving experience overall than regearing to 3.73s.

Thank you, i will look into that. It is a bit pricer at $3500. Would that bolt right in? or would there need to be mods?

 

[Mark Jennings]

Cost depends on your skill set. 2 sets of ring and pinion gear sets, 2 sets of bearings and seals….if you do the work yourself, you’re probably in it a $1000. If you shop it out, double that cost. You can reuse the carrier and spiders, but if they’re worn, than add another couple hundred. There may be other costs, depending on the pinion spline, you may end up also having to purchase universal u-joint flanges.

 

[pb4ugo]

There's a couple of ways to go about it. You can find 3.70 3rd members out of a later fj60 or 40 and swap them in. You might need to buy new pinion flanges to match your driveshaft bolt pattern. Or buy ring and pinion sets and install kit and install the gears in your existing 3rd members. The latter costs more. You can find an rpm calculator and play with numbers. Be sure to measure your actual tire size when using the calculator. Compare the #s to what you have now.

 

[Tigerstripe40]

Thank you, i will look into that. It is a bit pricer at $3500. Would that bolt right in? or would there need to be mods?

It's quite a bit more than that, to be honest. You need to change out the transfer case as well, but it will bolt up to the 2F '4 speed' bellhousing. There are modifications you'd need to do to the transfer case hump, modify driveshafts. It's not really too bad of a mod.

But it would increase overall drive-ability significantly, and keep the 4.11s in case you want to go with a larger tire or possibly even decide to do some more offroading.

OEM H55F Transmission & T-Case Assembly - Fits 1958-1990 Land Cruiser With Modifications (H55FCOMBO)

Land Cruiser OEM H55F Transmission & T-Case Assembly

cruiserteq.com

 

[brian]

i sourced 3:70 3rds from another cruiser, and then just swapped the whole 3rd. put the front in the rear and vice versa. one of the single greatest things i did to mine.
fj60s have the same gearing.
i have 33s under mine and it cruisers just fine on the interstate....its a driver not a wheeler.

 

[brian]

the reduced rate of acceleration is a bit of a non issue on a 50 year old 135hp engine.

 

[CondeCruiser]

I just got some 3.70 3rds from an FJ60. Going to be swapping them in my '76 in a couple weeks. Same thing as above. Going to put the front in the rear just as @brian did.

 

[JKIII FJ40]

I did something similar, started with a stock 74 3spd and 235/85r16 tires (32in I believe). I swapped in a H42 from a FJ60 (34mm Split case) and ran the 4.11's for a while. While on the prowl for stuff I got real lucky and found the axles out of an 81 that had the 3.70's and rear axle parking brake. I still need to hook up the rear parking brake but so far I like the 3.70s with my combo. With my set up it starts off smooth and I am evenly spaced and its not screaming at 65. I can notice that I have less stomp and go but then again I am never really in a hurry. Eventually I may swap in a 5spd with a 3 to 1 transfer case.
Finding a set of pigs from a 60 is still doable and everything else can be done in a weekend or two. In the event it doesnt work out, you can always pull the pigs and sell them.
What I didnt see in the post is what size tires you are running. 31s I would say do the pig swap, 33s I would leave the 4.11s.