H41 or H42..

splitshot · 06-03-09, 07:35 PM

I've got one or the other sitting in the shop to eventually go in the 40. Any external differences to I.D?
Also, all I got from searches is a difference in gearing, can anyone expand on it?
Third, I am missing the shifter, where would you suggest?

Poser · 06-03-09, 07:47 PM

Quote:

Originally Posted by splitshot

Any external differences to I.D?

Nope.

Put it in first gear and count the input shaft rotations compared to the output shaft rotations...

Quote:

Originally Posted by splitshot

Also, all I got from searches is a difference in gearing, can anyone expand on it?

Gearing expanded... <---- this is a link

Quote:

Originally Posted by splitshot

Third, I am missing the shifter, where would you suggest?

Shifter cane, or whole top cover?

Wanted section...

splitshot · 06-03-09, 08:01 PM

Quote:

Originally Posted by Poser

Nope.

Put it in first gear and count the input shaft rotations compared to the output shaft rotations...

Gearing expanded... <---- this is a link

Shifter cane, or whole top cover?

Wanted section...

Thank you sir

, good info as usual..

Just the shifter rod/cane. Challange is to find first gear without the shifter..

splitshot · 06-03-09, 09:27 PM

Quote:

Originally Posted by Poser

Gearing expanded... <---- this is a link

So, correct me if I'm wrong, I'm looking for 4.9/1, 5.2/1 or 3.5/1?

For 1st gear..

amaurer · 06-03-09, 09:34 PM

Quote:

Originally Posted by splitshot

So, correct me if I'm wrong, I'm looking for 4.9/1, 5.2/1 or 3.5/1?

For 1st gear..

4.9:1 for the H41
3.5:1 for the H42

There isn't much bad to say about the H41, you get a lower first which never hurts and its still plenty usable on the road - if you have one I don't know why you wouldn't use it.

splitshot · 06-03-09, 10:07 PM

My 3 speed is even lower at 2.7:1..(If I read that right).
I'm going to be replacing the 'ol f with a 2f, why would I want to put a higher ratio 4 speed instead of using my exhisting gears?
Sorry, I know this has been hammered before, but couldn't find any convincing answers..

cruiser_guy · 06-04-09, 06:50 AM

Quote:

Originally Posted by splitshot

My 3 speed is even lower at 2.7:1..(If I read that right).
I'm going to be replacing the 'ol f with a 2f, why would I want to put a higher ratio 4 speed instead of using my exhisting gears?
Sorry, I know this has been hammered before, but couldn't find any convincing answers..

Wrong. You 3 speed is HIGHER. For every rotation of the crank, your three speed in first puts out 2.7 rotations. The H41 puts out nearly 5 rotations, almost twice as low!

The H41 and H42 top cover should interchange as the shifting pattern is identical.

pjohnson · 06-04-09, 09:23 AM

Quote:

Originally Posted by cruiser_guy

<snip>
The H41 and H42 top cover should interchange as the shifting pattern is identical.

The top covers will interchange, but there can be slight differences in the width of the shift forks. I could not use an H42 cover on my H41 because one of the shift forks was about 1.5mm too wide for the shift collar. The shift forks were not interchangeable on mine because the shift fork shafts were different diameters.

Also, the shifter cane is matched to the cover. The one piece cover requires a shorter shifter cane input than the two-piece cover. My H41 had the one piece top cover.

FWIW, my H41 supposedly came out of a Japanese Firetruck with a 2F.

Phil

MtnTrucker · 06-04-09, 10:52 AM

I currently have a worn out F.5 with an H42 and orion 4-1 TC behind it. I run 37's with 4.88 R&P. I'm getting ready to drop my new 2F in and am considering picking up an H41 to replace the H42 at the same time.

From my reading I'm assuming this would give me a much improved 1st gear for rock crawling in low range in conjunction with the Orion. Since the Orion is so low geared in low range, I'm thinking there may be times I will want to run in 4 high but have the lower 1st gear of the H41 in case I encounter a mild obstacle and dont want to stop and shift into low range.

Are my assumptions correct? Is there enough difference between the 41 and 42 first gear to make it worth the additional cost of buying a 41? It seems like the average price of 41's is around $650. I'm tempted to go sm420 to get a really super low 1st gear but I dont like dealing with adaptors and such. The 41 is nice because it's basically a direct bolt in.

I hope this isnt a highjack and sort of expands on the question in the original thread.

splitshot · 06-04-09, 11:03 AM

No highjack at all, Mtn. Good question.

Quote:

Originally Posted by pjohnson

The top covers will interchange, but there can be slight differences in the width of the shift forks. I could not use an H42 cover on my H41 because one of the shift forks was about 1.5mm too wide for the shift collar. The shift forks were not interchangeable on mine because the shift fork shafts were different diameters.

Also, the shifter cane is matched to the cover. The one piece cover requires a shorter shifter cane input than the two-piece cover. My H41 had the one piece top cover.

FWIW, my H41 supposedly came out of a Japanese Firetruck with a 2F.

Phil

So, from what I'm getting, I need to pull off the top cover, and find 1st gear before I look for a shifter cane, because they won't interchange?

pjohnson · 06-04-09, 01:26 PM

Quote:

Originally Posted by splitshot

No highjack at all, Mtn. Good question.

So, from what I'm getting, I need to pull off the top cover, and find 1st gear before I look for a shifter cane, because they won't interchange?

Use a big-a$$ screwdriver to put it in first gear

If you have the cast one piece top cover, you can use a 3sp shifter cane and shorten the input end to fit. That is what I had to do.

If you have the 2 piece top cover where the shifter tower is bolted on to the cover, you should be able to use any readily available H42 shifter cane.

Also, if you have the 2 piece top cover, I would check to be sure it's an H41.

Post a couple pics...

Phil

mustardfj40 · 06-04-09, 01:37 PM

My H42 top cover works perfectly with my H41 tranny, I did not have to modify or even adjust anything.

mustardfj40 · 06-04-09, 01:42 PM

Quote:

Originally Posted by MtnTrucker

Are my assumptions correct? Is there enough difference between the 41 and 42 first gear to make it worth the additional cost of buying a 41? It seems like the average price of 41's is around $650. I'm tempted to go sm420 to get a really super low 1st gear but I dont like dealing with adaptors and such. The 41 is nice because it's basically a direct bolt in.

Aren't you supposed to modify your drivelines with the SM420?

nickwood48 · 06-04-09, 02:02 PM

Quote:

Originally Posted by cruiser_guy

Wrong. You 3 speed is HIGHER. For every rotation of the crank, your three speed in first puts out .37 rotations. The H41 puts out nearly .2 rotations, almost twice as low!

The H41 and H42 top cover should interchange as the shifting pattern is identical.

FIXED it for ya

splitshot · 06-04-09, 04:46 PM

Quote:

Originally Posted by pjohnson

Use a big-a$$ screwdriver to put it in first gear

If you have the cast one piece top cover, you can use a 3sp shifter cane and shorten the input end to fit. That is what I had to do.

If you have the 2 piece top cover where the shifter tower is bolted on to the cover, you should be able to use any readily available H42 shifter cane.

Also, if you have the 2 piece top cover, I would check to be sure it's an H41.

Post a couple pics...

Phil

Looks to be a H42, getting 3 1/2 rotations~ in 1st gear.

Here's a pic of the crusty thing..

splitshot · 06-04-09, 05:10 PM

Another question: I know the switch on the back of the trans is the back up switch, but what is the lead that is on the top cover?

pjohnson · 06-04-09, 11:44 PM

Quote:

Originally Posted by mustardfj40

My H42 top cover works perfectly with my H41 tranny, I did not have to modify or even adjust anything.

I suspect this is probably more common than my situation and leads me to believe my H41 truly did come from a Japanese model.

Phil

Fast Eddy · 06-05-09, 01:52 AM

Quote:

Originally Posted by splitshot

Another question: I know the switch on the back of the trans is the back up switch, but what is the lead that is on the top cover?

That's a '78 high-gear indicator. It eventually connects to the emissions computer. One year only for AFAIK. If you don't need it you should see if someone like SOR would want to trade you for a different top-cover as a good cruiser deed. I swapped this cover onto my H41 without any trouble, so I have an H41 with the high-gear indicator now.

fj40taz · 06-05-09, 06:34 AM

I am picking up an H42 for my 74 to install behind the 350.. right now it has a 3 speed tranny..

splitshot · 06-05-09, 06:38 PM

Where is the best place to get the gear/bearing/seal to do a 4 into 3 conversion? Kurt?

Poser · 06-05-09, 07:48 PM

Quote:

Originally Posted by cruiser_guy

Wrong. You 3 speed is HIGHER. For every rotation of the crank, your three speed in first puts out .37 rotations. The H41 puts out nearly .2 rotations, almost twice as low!

The H41 and H42 top cover should interchange as the shifting pattern is identical.

Quote:

Originally Posted by nickwood48

FIXED it for ya

What are you talking about?

The input shaft is coupled to the engine via the clutch disc and pressure plate combination. When the clutch pedal is released and the friction disc is clamped to the flywheel by the pressure plate, it rotates at the same speed as the crankshaft. For every one revolution of the crankshaft the clutch disc and transmission input shaft will rotate once as well.

When a Toyota J30 three-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 2.7 times.

When a Toyota H41 four-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 4.9 times.

When a GM SM420 four-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 7.05 times.

jagota · 06-05-09, 10:08 PM

Thank You Poser.

malcb · 06-06-09, 04:55 PM

Quote:

Originally Posted by Poser

What are you talking about?

When a Toyota H41 four-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 4.9 times.

3000 rpm * 4.9 = 14700 rpm
3.7 diff so 14700/3.7 = 3972 rpm at wheels
Stock 31" tire so 31 * 3.14 = 97 inches * 3972 = 6 miles a minute or 336 miles an hour?

or

3000 / 4.9 = 612 rpm
3.7 diff so 612/3.7 = 165 rpm at the wheels
97 * 165 = 15 miles an hour

amaurer · 06-06-09, 06:22 PM

Quote:

Originally Posted by malcb

3000 rpm * 4.9 = 14700 rpm
3.7 diff so 14700/3.7 = 3972 rpm at wheels
Stock 31" tire so 31 * 3.14 = 97 inches * 3972 = 6 miles a minute or 336 miles an hour?

or

3000 / 4.9 = 612 rpm
3.7 diff so 612/3.7 = 165 rpm at the wheels
97 * 165 = 15 miles an hour

Yep, first through fourth are reduction gears. 4.9 turns output would be a one hell of an overdrive!

nickwood48 · 06-09-09, 02:01 PM

Quote:

Originally Posted by malcb

3000 rpm * 4.9 = 14700 rpm
3.7 diff so 14700/3.7 = 3972 rpm at wheels
Stock 31" tire so 31 * 3.14 = 97 inches * 3972 = 6 miles a minute or 336 miles an hour?

or

3000 / 4.9 = 612 rpm
3.7 diff so 612/3.7 = 165 rpm at the wheels
97 * 165 = 15 miles an hour

Exactly - for every 1 rotation your get .2 at the output (1/4.9).

Pin_Head · 06-09-09, 02:59 PM

Quote:

Originally Posted by Poser

What are you talking about?

When a Toyota J30 three-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 2.7 times.

Actually, for every revolution of the output shaft, the input will rotate 2.7 times.

nickwood48 · 06-09-09, 06:32 PM

Quote:

Originally Posted by Poser

What are you talking about?

The input shaft is coupled to the engine via the clutch disc and pressure plate combination. When the clutch pedal is released and the friction disc is clamped to the flywheel by the pressure plate, it rotates at the same speed as the crankshaft. For every one revolution of the crankshaft the clutch disc and transmission input shaft will rotate once as well.

When a Toyota J30 three-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 2.7 times.

When a Toyota H41 four-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 4.9 times.

When a GM SM420 four-speed transmission is in first gear, for every one revolution of the input shaft, the output shaft will rotate 7.05 times.

Your all bassackwards poser.

If your engine RPM was increased, like your saying, you would have an overdrive.