The right 4 speed tranny for my FJ40??? SM420?? (1 Viewer)

[Ojungle]

HI guys, here is a question for you. I have a 1973 FJ40, I love that thing, right now it has a 3 speed tranny behind a 305 chevy motor. So here is my question:
I want to install a 4 speed tranny, is it easier for me to just put a 4 speed chevy tranny than a 4 speed 74- up FJ40???
If it is easier, is it the SM420 the one I need?? and If I use a SM420, what adaptors do I need? I know I will not need a adaptor for the motor, but do I need one for the transfer case??
Thank you for your knowledge guys!
God bless!
Jorge

 

[green40]

You'll need an adapter plate to go between the 420 and 3 speed case.
Not sure if you'll have to change driveshaft lengths or not.
There are write-ups on this in the tech section.

 

[Bigmoose]

Why not use a sm465 4 speed, they are easier to find and stronger. Either tranny you'll need a chevy bellhousing, clutch fork, throw out bearing and chevy tranny to toyota transfer case adapter, just make sure the replacement tranny is an 10 spline output shaft. BIGMOOSE

 

[cyclocrossen]

If you are interested I have a sm 420 tranny with bell housing, shift fork, new centerforce clutch, 4speed transfercase and aa adapter to mate the two. I bought it off here from orange_45 for 600 but would take 500 plus shipping if desired. If you are interested I will send some pics.

 

[JasonH]

Why do you want the 4 speed? A 420/465 will get you a great granny gear for off-road, but you'll still drive it on the street like a three speed.
If you're looking for driveability, get a Cruiser 4 speed.

 

[Shawn Russell]

I would do the swap for the added strength of the 420/465.

Shawn

 

[Ojungle]

Hey Jason, thank you so much for your response, so here is another question, some one has bee helping a lot and this person mentioned to me the problem about the toyota 4 speed tranny is to fit behing the 305 V8, is that true? if is not hard, what do I need to be able to use a Toyota 4 spped tranny?. I really want to be able to get rid off that 3rd gear noise ( is is too noise).
God bless!
Jorge

 

[Ojungle]

to be honest, I do off road stuff but not enough, this fj40 is my driving car so I do want more driveability with the 4 apeed, so, is the 420 better for me for that purpose or the TOYOTA 4 speed?
God bless all!
Ojungle- Jorge

 

[Cruiserdrew]

Why do you want the 4 speed? A 420/465 will get you a great granny gear for off-road, but you'll still drive it on the street like a three speed.
If you're looking for driveability, get a Cruiser 4 speed.

This is true, but....

I have 8 years of experience driving an FJ40 with an SM420. It is indeed a 3 speed plus a granny first. If you do any 4 wheeling at all, this tranny will improve your capabilities more than anything else you can do for the same $$. I also have a 465 partially torn down in the garage for comparison.

The basics:
SM420 1st gear 7:1
SM465 1st gear 6.55:1
H42 (Common USA LC 4 speed) 1st gear 3.5:1
H41 (Uncommon in US) 1st gear 5:1

A couple of comments:

The SM420 second gear, is about the same as an H42 first gear, so starting from a stop on the street, is no big deal. Both 420 and 465 are not syncronized in 1st gear, so you must be at a complete stop to shift into 1st.

There is a wide spread in SM420 between 3rd and 4th, which in a Land Cruiser, with the narrow rev range of the motor, can at times be a pain. With that said, I've traveled all over the Sierras in mine. Some of the long grades I do at 35 MPH in 3rd.

Both the SM420 and SM465 are better built and far stronger than Land Cruiser 4 speeds. Both were used in up to 2 1/2 ton trucks. The gears are huge in comparison to the H42. The price you pay for all that massive gearing is that it is heavy and shifts slowly.

THe advantages of the SM420 are that it's shorter(2 inches) and lighter(125lbs vs 175 lbs) than an SM465. It still is significantly heavier than Cruiser 4 speed(75 pounds roughly). It's true you will need a Chevy bellhousing but these are a dime a dozen in a yard. If you go with SM420 you need the older style with the smaller hole for the front bearing retainer.

SM420s almost all came with the 10 spline output, which is what you need to adapt to Cruiser 3 speed transfer. Only a small minority of 465s come with a 10 spline output, and many of those are boogered up-for some reason the 10 spline outputs get damaged in routine use, so check carefully before you buy or just get a new main shaft. Most SM465s will have a 35 spline shaft. Now I believe I saw that AA had an adapter for SM465 35 spline to Land Cruiser 19 spline split case. That would not be a bad combo.

The SM465 does appear to be even heavier duty than the SM420, but it weighs 50 pounds more. I can't pick it up by myself. It seriously was Gm at it's best. Not a big deal, just remember it's a beast and don't hurt your back fawking with it.

On balance, I believe the SM465 is a slightly better choice for 1 reason: it doesn't have the reverse hump in the way of your front drive output, but the SM420 is a fine choice that works great with the bonus of an even lower 1st gear. Get which ever one is most available.

If this is going in an FJ40, I strongly recommend you use a "plate style" adapter. The Advanced adapter unit adds significant length, which is OK in a wagon but in a SWB 40 you don't have much room to play with it.

So if you want to keep your existing transfer case, either the 420 or 465 is a great choice. If your truck is mostly a pavement pounder, stick with a Cruiser 4 speed. For a while OrangeFJ45 had an H41 + split case that was prepped and ready to go at a good price. That's almost the best of both worlds with the 5:1 low and the strength of the split case. It would be a bit more money, and you might need a different bellhousing/adapter but it would be awesome. If you have a bit of available cash, call Georg at Valley Hybrids and grab that unit before I do.

Good luck, there are really no "bad" choices here. How much do you want to spend?

 

[cruiser enthuiser]

Wow, that's some great information Drew ^^^ thanks for sharing. I'm pondering options to replace the stock 3spd trans and tc that's behind my SBC 350. Actually have a sm465 sitting in the garage but I think I'd rather mate it to a 4 speed transfer case as I'm not a big fan of the vacuum shift 3spd.

Anyway, thanks again, hijack over.

Ed

 

[Cruiserdrew]

I don't believe the SM465 is 175lbs... more than likely 140ish at worst. An NV4500 is 195lbs and a SM465 isn't close. I had an easier time throwing around a SM465 than NV4500

:

You're just stronger than you think:

Quoted from some Offroad Mag:
(Unfortunately the table thing didn't come through but you get the idea



SM465 vs. SM420
If it's a toss-up between running an SM420 or an SM465 in your truck, you may want to consider going for the easier-to-find-and-get-parts-for SM465 if it will physically fit.


SM465
SM420

Length(in.)
12.0
10.4

Height (in.)
18.0
17.0

Weight (lbs.)
175
135

Input Shaft
1 1/8-in., 10-spline or
1 1/2-in., 10-spline
1 1/8-in., 10-spline

Output Shaft
10-spline (early 4WD),
35-spline (2WD)
32-spline (late 4WD)
10-spline

BearingRetainer Diameter (in.)
5.125
4.686

GearRatios



1st
6.55:1
7.06:1

2nd
3.58:1
3.58:1

3rd
1.7:1
1.71:1

4th
1.1:1
1.1:1

Reverse
6.09:1
6.78:1

 

[JasonH]

I have 8 years of experience driving an FJ40 with an SM420.

As do I. For what I use my Cruiser for, it's perfect and I don't mind the way it drives on the road at all. And for the record I agree with everything you guys have said so far. A lot of very good information.

Based on Jorge's desires for a more streetable and quieter transmission, I still think the Cruiser 4 speed is the way to go. As far as strength, I doubt his 305 is going to stress that tranny too much. I've never seen anyone break a Cruiser tranny (although I'm sure it's happened), and I'm on my 4th SM420.

Good luck either way!

 

[pb4ugo]

My only recommedation is if you go w/a sm420 get the bellhousing and throw out bearing fork too.
As mentionrd b4. The Toyota 4 speed shift easy and you can basically slap gears. You have to be more percise in your shifting w/the 420/465. I used to run the AA bellhousing for the SBC/toy 4 speed trans w/ no problems. I'm not familar w/adapting a 3 sp case to anything . The only thing I do know is the 3 speed case has a lower gear ratio than the 4 speed case which would be a good thing especially if you run the toy trans.

Cruiserdrew your ratios are out of wack

SM420 7.05/3.58/1.71/1 :1
SM465 6.55/3.58/1.57/1 :1

If there is an issue w/the 420 it would be the spred between 2nd and 3rd.

 

[Cruiserdrew]

My only recommedation is if you go w/a sm420 get the bellhousing and throw out bearing fork too.
As mentionrd b4. The Toyota 4 speed shift easy and you can basically slap gears. You have to be more percise in your shifting w/the 420/465. I used to run the AA bellhousing for the SBC/toy 4 speed trans w/ no problems. I'm not familar w/adapting a 3 sp case to anything . The only thing I do know is the 3 speed case has a lower gear ratio than the 4 speed case which would be a good thing especially if you run the toy trans.

Cruiserdrew your ratios are out of wack

SM420 7.05/3.58/1.71/1 :1
SM465 6.55/3.58/1.57/1 :1

If there is an issue w/the 420 it would be the spred between 2nd and 3rd.

Behind a tired 2F, it's the spread between4th and 3rd that's the problem, trust me.

 

[pb4ugo]

Behind a tired 2F, it's the spread between4th and 3rd that's the problem, trust me.

I believe you, I've heard the same thing from many. Thank you for the correction. The comment "of out of wack" was on the gear ratios you posted for the 465 & 420.

 

[craptabulous]

personally im big on at least a 6:1 first gear , i never use 4 low with my 420 .

i was pretty pissed off when i stalled it in the mud in second gear the other day . that 7:1 sure is nice . i have never had a problem with my 420 once i fixed the clutch .

420 or 465 will both work great .

if you don't take it offroad then just get the cruiser 4-speed , im not a fan of them since i have one sitting in my backyard with half the output splines gone . but if its a road cruiser and your not sinking it to the floor in mud on 37's then you should be just fine .

 

[shelfboy1]

ive sank mine in mud with 38s for many years ,about 30 years with the same 4 speed and it still works fine ,also plow snow with it and have front and rear lockers.it was my dd until 2 years ago until i bought a one ton chevy to tow with instead of the fj 40 .good luck on what ever choice you make

 

[Ojungle]

wow, thank you so much to everyone!. I am learning so much! So what you guys are saying is that a 4 speed Toyota is more for street but the sm42 is more powerful for off road, right? I will not mind to have the best of both worlds, So if to leave it the way it is is the best, then I will do that.
The things is that my Tranny is really noise in 3 gear.
God bless!
Jorge

 

[Ojungle]

thanks Lil'John! so it has lower grae, what about street, will it make tranny noise better?, are this SM420 or SM465 4 speed ot they are still 3 speed like my current tranny?
Thanks and God bless guys!
Jorge

 

[marks69cruiser]

Love my 420! Here is a link to some cool info:
Novak Jeep Conversions - Home
Good luck!!