H41 or the SM420

[VinSil]

I have been searching and have read various opinions on the subject...would like some solid first hand advice.

First off, specs on the rig:


72 FJ40, 2F, H41, 3 speed case, 4.56 gears, 37's.


Rig is not a daily driver, but does drive to the trails.


I came from a twin cased Runner with 4.7's in the rear case and really miss my stupid low for the rocks and technical stuff. Even though this FJ40 won't see the same rock gardens, I want some lower gears.


So, I bought a SM420 today with the AA kit and 3 speed case on it. Now....I'm having some second thoughts.


I have nice, built driveshafts I don't really care to modify. I need to pull my H41/case out now as they are both leaking and my rear main is leaking too. It's coming out either way, so I figured I would gain my stupid low with the SM420.




Is this a worthwhile swap? I keep reading about the very unfriendly road manners the SM420 has, the driveshaft mods (was thinking of selling off the AA adapter and getting a plate if I can find one), and the other small parts/fab work it will take to put it in.


I guess I need a heck yes..worthwhile or...not worth my time. And no, I do not have 2k to drop for an Orion...even though that would be my bolt in fix for lower gearing without any mods.

 

[Poser]

If you really like the smooth shifting H41 on the road, you are not going to like the three-speed functionality of the SM420 on the road.


Your best bet would be to purchase an Orion and put that behind the H41, if you want a nice shifting transmission on the road.


If you do not care that you are going to be installing an older style transmission that will likely be noisier than your H41 that has a wider spread between second, third and fourth gears compared to your H41, then it really does not matter, because you will really enjoy the 7.05:1 first gear of the 420.


If you are not really going to be pounding rocks and will be spending more time on pavement, you are likely not going to be very fond of the 420/three-speed transfer case combination.

 

[Pin_Head]

The 420 first gear is only 30% lower than the H41. Get an Orion if you want to really notice the difference.

 

[marks69cruiser]

I am stoked with my 420. With a 2f motor, and 37"s going to and from the trail I dont think you will regret the swap. I drive my light duty 5 spd heep cherokee to work and back. So I appreciate having a heavy duty tranny in my cruiser. Good luck.

 

[VinSil]

I know, it seems simple but in the end...I don't want to regret this especially since the H41 is not a very easy transmission to source.


I do enjoy my smooth shifting transmission now. (well, everything but the reverse pattern but that is easy to get used to).

I would hate to step backwards, and really didn't consider the gap of the ratios of the 420...it's not like I have huge amounts of power and torque to overcome those gaps..I do not plan to do a V8 anytime. I am considering propane and a small snail for a bit of a boost though.


Maybe I should just dump the 420/adapter and save for the orion.

 

[craptabulous]

i find the 420 can be great one day and then a total pain in the ass the next day . i also think my 420 must have issues .

shift it slow and you wont have a problem , shift it fast and it will grind .

i would sell them both and get a nv4500.

 

[Cruiserdrew]

My FJ40 is basically a trail truck only. Honestly, the SM420 rocks. 7:1 is better than 5:1.

The SM420 doesn't shift that bad and isn't that loud, but it does feel heavy duty and slow shifting. It is totally the right tranny for off-road duty.

Anyway, not a bad choice. I would not swap my SM420 for an H41, but I would at least consider swapping an H41 for an SM420.

With that said, an H41 with an Orion would be awesome, though most of the gears would be too low.

 

[VinSil]

That is my fear, being TOO low for most situations. I found that the combination of the dual cases, I had a perfect gear for everything. I don't have that luxury with this rig. That is why I was heavily considering the 420, and bought one. Figured I would deal with the issues it has, for the gain of that first gear. I'm tall geared enough now I use 1st with the H41...I think the 420 would just be too low for that sort of thing I might be putting my rig into "serious pig" status by effectively losing a gear.


Arg.



Sell both and buy a 4500? Sure...and after the adapters/cutting/mods I'd be better off just swapping the whole drivetrain out! I would love one...believe me! I just think it would cost more than a Orion in the end with all the work and money it would take to make it work.

 

[Poser]

Balance and compromise.

It all comes down to what you really want to do with your truck.

 

[FF LC FREAK]

Hey Vinsil! I think you know what my vote is. Put in the SM420 and don't look back. Besides, I know someone who would take that H41 off your hands!

 

[handcannon]

VinSil

You might consider putting a toybox or rockbox between your H41 and TC. As you already know this will increase your driveline length, requiring front and rear driveshaft mods. But, if you either flip your rear springs or use 60 series rear springs you will move the axle back about 3 1/2 inches gaining back about half of what the toybox will add to your driveline length.

Don

 

[VinSil]

Freak...oh don't I know! I will let you know soon here!



I have considered the toy box as well. I have 55 springs in the rear right now so I "think" I might have enough room to make something like that work.




Thanks for the advice all. I've got some choices to make!

 

[pjohnson]

I'm with Poser's first post....

I just switched from an SM420/Dana18 to an H41/Toybox/4spTcase.

The 420 was great for the rock gardens and it never gave me issues (after Marlin rebuilt it). BUT, it was LOUD and shifting always required being careful.

The H41 is smooth and quiet. With the 4.7 Toybox, I'll be running 94/1 for most rock crawling with the option of a stupid low of 184/1

If I had to start over... I would put an Orion behind the H41 in a heartbeat. (I have had my parts on the bench for 3 years).

my .02,
Phil

 

[VinSil]

Thank you Phil for the input.

 

[handcannon]

I have 55 springs in the rear right now so I "think" I might have enough room to make something like that work.

I would love to see how you did your 55 springs sometime. I am collecting parts to do 55's front and rear and also 60 series axles. I live just across the freeway from you. I'm the guy in the crusty ol' red 40 who stopped one evening last fall and talked to you.

Don

 

[VinSil]

Oh yes, I remember you Don.

I'm off Mon-Thursday, so your welcome to stop sometime and check out the springs.

I can also give you a few pointers on the 60 series axles (put the rear in mine, was going to put the front in but decided to keep the 40 and just do the IFS hub conversion to make it the same width without having to redo my steering links/spring mounts up front).

Let me know...just shoot a PM or something.