FJ40 speed/ RPM

[Tommy Shumpert]

So I was wondering if this is the typical for everyone running this setup.
I have never driven a 40 before or owned one before the current one I have, so really don’t have any reference.

F2 sniper, 3.70 gears, 4th gear 2400 RPM @ 65 MPH. On 33” tires.
So when your taking long road trips 65, and sit back and chill?

Also, if going to a 5 speed, would that make a much bigger difference?

Thanks!

 

[fireflyr]

Sounds correct. The H55 5 speed is .845 - 1 ratio and I believe the 4 speed is 1.0 to 1.

 

[CruiserInProgress]

Not your setup, but offered as a point of reference, my desmogged, but otherwise stock 79 with 2F, 4-speed, 3.70 diff on 31" tires, I run 2500 rpms for hours at 62mph. Seems fine, with no overheating.
I occasionally, bump it to over 70+ for passing, which probably surprises some folks, me included!

 

[JohnnyC]

F2 sniper, 3.70 gears, 4th gear 2400 RPM @ 65 MPH. On 33” tires.
So when your taking long road trips 65, and sit back and chill?

Also, if going to a 5 speed, would that make a much bigger difference?

If you kept everything else same and went from a 4 to a 5 speed the difference would be an increase of 10mph at 2400rpm

Your 4 speed 65mph at 2400
If go 5 speed 75mph at 2400

I did a looksie over here:

Gear Ratio Calculator

@JKIII FJ40 got me into using that site and now it’s my go to for mind numbing tranny and diff senerios lol

 

[JKIII FJ40]

If you kept everything else same and went from a 4 to a 5 speed the difference would be an increase of 10mph at 2400rpm

Your 4 speed 65mph at 2400
If go 5 speed 75mph at 2400

I did a looksie over here:

Gear Ratio Calculator

@JKIII FJ40 got me into using that site and now it’s my go to for mind numbing tranny and diff senerios lol

you can spend hours on that site for various combinations of drivetrain options

 

[Chamba]

I'm a big fan of the H55. Especially for your setup. I assume you've got the H42 4 speed, so the H55 gives you the lower 1st gear of the H41 PLUS a 15% overdrive.

With the 4.10 axles and an H55 you'll rarely use 1st gear (it's really a granny low). But with the 3.73, you'll use it like any other 1st gear.

With your 33" rubber, the H42 will feel a little boggy at times in first gear on hills, etc. The H55 will solve that and give a very nice cruising rpm. Rather than look at it as giving you another 10 mph, look at it as giving you a quieter ride at the same speed. At 65 mph, you'll be turning 2050 RPM, which truly is the sweet spot for the 2F.

 

[ceylonfj40nut]

I'm a big fan of the H55. Especially for your setup. I assume you've got the H42 4 speed, so the H55 gives you the lower 1st gear of the H41 PLUS a 15% overdrive.

With the 4.10 axles and an H55 you'll rarely use 1st gear (it's really a granny low). But with the 3.73, you'll use it like any other 1st gear.

With your 33" rubber, the H42 will feel a little boggy at times in first gear on hills, etc. The H55 will solve that and give a very nice cruising rpm. Rather than look at it as giving you another 10 mph, look at it as giving you a quieter ride at the same speed. At 65 mph, you'll be turning 2050 RPM, which truly is the sweet spot for the 2F.

FJ40s at 65mph/75mph will never be quiet. Recently did 2000 miles from Dallas to Ouray and back. 2F/4spd/33” tires/4.11. A healthy engine can take 2500 rpm+ all day. The 5spd gains are minimal with rubber overdrive IMO. Just settle in on the 4spd and flog it. It’s meant to be flogged.

 

[brian]

85 mph all day long

 

[JohnnyC]

85 mph all day long

In foam seat comfort

 

[brian]

In foam seat comfort

9 forward, 3 reverse gear combinations

 

[greenbeasty]

Y’all‘s 40s must steer and stop better than mine, if you got the balls to do 85 miles an hour down the road!!

 

[Tommy Shumpert]

So at this point, sounds like spending 5k for 5 speed isn’t really worth it. If I had it laying around….

 

[1911]

3.70 gears, 4th gear 2400 RPM @ 65 MPH. On 33” tires.
So when your taking long road trips 65, and sit back and chill?

My set up also; the answer is “yes”, that is exactly what I do.

It will go 75 or a little more if I have to, but on highway trips I try to stay on secondary roads where 65 mph is easy and not a bother to other drivers.

 

[JohnnyC]

Y’all‘s 40s must steer and stop better than mine, if you got the balls to do 85 miles an hour down the road!!

My steering has been good and bad at times… my brakes had been good when I went disc 29 years ago … I had my 40 up to low 80’s before

Funny thing is my 74’ owners manual says maximum cruising speed is 63 mph

Sooo somebody is lying

Can definitely cruise faster than 63 and 85 mph all day long … hmmmm … I wouldn’t lol

Edit: picture from my owners manual

 

[1911]

Y’all‘s 40s must steer and stop better than mine, if you got the balls to do 85 miles an hour down the road!!

Four-wheel disc brakes and caster corrected with shims helps a lot. But yeah, the short wheel base and no sway bars does not bode well for modern freeway speeds.

 

[sogncab]

Also, if going to a 5 speed, would that make a much bigger difference?

About 600rpm.

 

[Living in the Past]

85 mph all day long

Most viewing this thread this wouldn't realize this wasn't a 2F but rather the powerful F135 with a one barrel carburetor. Can't expect the 2F to match those numbers.

 

[Living in the Past]

In foam seat comfort

Don't want to post that video here. Enough people are already dumping their 2F and putting in a F135. Getting hard enough finding F135s. This will just make it worse.

Disclaimer: do your own research before pulling your 2F in favor of the F135.

 

[brian]

Don't want to post that video here. Enough people are already dumping their 2F and putting in a F135. Getting hard enough finding F135s. This will just make it worse.

Ive got 2 on stands in the garage...call them my nest eggs.

 

[desmocruiser]

It is nice but isn’t as necessary in a 79’ and later FJ40 and FJ60 due to the friendlier highway gearing where a solid example will still cruise in the high 60’s and occasional Low 70‘s with the 4 speed.

I have an H55 both in my 87’ FJ60, which has gearing similar to a 79’+ FJ40 (I owned one of those for 7+ years) and my 78’ FJ40 with stock 4:11 gearing. I can already see the lower geared 40 stays in 5th far more often than the FJ60, it is nice in the 60, but most hills require a dip back to 4th gear in my part of the world, but few 2F’s are hill friendly!

To address the earlier top speed question, a Built 2F and H55 5 Speed in earlier late model 40’s is a great combo for the highway, “If” the rest of the truck is set up to comfortably cruise in the 70-75 MPH range and reach 80+ if needed, but you do feel each one of those MPH’s!

Plus, the H55 not only provides an OD highway gear, but the first 3 gears are lower, helping acceleration, overall beneficial, almost like a regular car.

I am very happy with mine, but alot went into getting it there and it’s the combination of motor, trans, and gearing that makes it all work well together.