So I know there are threads about this topic but who here has switched from a 3 spd to 4? Was there a big difference besides having 4 gears. I use my cruiser as a daily driver and it already has a 2f in it. I would love to get a h55f but that would require winning the lotto. Will it bolt up with my transfercase? I know I need to cut a hole in the floor. But it just can't be this simple and noticeable in driving. Or is it?
Converting from 3spd to 4spd
- Thread starter Bigcity25
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Much better manners in traffic, liwer first gear, top ratio is the same so no more top end speed. Shifts smoother, synchro-ed 1st gear. You need bellhousing, new clutch and flywheel and driveshaft mods.
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Different bell housing and driveshaft mods yes. But you don't need to switch clutch, flywheel and pressure plate. You just need to use either three speed or four speed parts. can't mix the two. You will also need to get a different input gear and special bearing to use the three speed transfer with the four speed transmission to use your old transfer case. The three speed transfer case is 2.313 low gear ratio as compared to the 1.992 low gear ratio in the four speed transfer case. First gear in the three speed is 2.757 to 1. The H42 four speed is 3.555 to 1. Being full svnchro and the better gear split make it a far better daily driver. When buying a H42 make sure you get one with a good tailshaft. Better to pay a little more for one that the tailshaft isn't worn where the transfer case input gear drives. Tailshaft aren't cheap and it's not simple to rebuild the H42.
I did the swap. It is a very noticeable improvement. When you get around to doing it, let me know if you need a hand or an extra set of eyes. In addition to the information here on MUD, here are a couple of threads on Rising Sun; my swap and Jeff Zepp's swap - both of these also include changing the engine. Fortunately, you will not have to do this.
Dropping the 3 speed transmission and t-case are very straight forward. Putting in the 4 speed and t-case will require tilting the engine because of the clearance issues with the frame cross member. Alternatively you could pull the engine, transmission and t-case out the front, then assemble it, then put it all back in as a unit. For what you are doing, I would recommend, just tilting the engine back.
Must have/must do items include;
You can keep your existing flywheel and clutch setup. If you decide to replace your clutch, then you will need to make sure your flywheel is appropriate for your clutch.
You can keep your existing t-case, but doing so will require you to get some additional parts (gears, bearings, longer bolts, etc.) so that it connects to the 4 speed transmission.
You can keep your vacuum shift system, but you may have to deal with some clearance issues. This is not that big of a deal.
Dropping the 3 speed transmission and t-case are very straight forward. Putting in the 4 speed and t-case will require tilting the engine because of the clearance issues with the frame cross member. Alternatively you could pull the engine, transmission and t-case out the front, then assemble it, then put it all back in as a unit. For what you are doing, I would recommend, just tilting the engine back.
Must have/must do items include;
- 4 speed bell housing
- Drive shafts; either modify the ones you have or get some from a 4 speed FJ40
- Pinion Flanges; many options but the key is the bolt pattern on drive shafts, third members and t-case need to all match up.
- Hole in the floor
You can keep your existing flywheel and clutch setup. If you decide to replace your clutch, then you will need to make sure your flywheel is appropriate for your clutch.
You can keep your existing t-case, but doing so will require you to get some additional parts (gears, bearings, longer bolts, etc.) so that it connects to the 4 speed transmission.
You can keep your vacuum shift system, but you may have to deal with some clearance issues. This is not that big of a deal.
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Only requires one gear and one bearing. You will need the spacer for the PTO gear or the PTO gear. Spacer behind the bearing and the four speed washer and stake nut. These are all common four speed parts. It's the inpit gear and bearing that are special. The thread pattern changed on the back of the of the transmission between the three and four speed which is the main reason you have to use different bolts. When buying a four speed you might try and get the fives bolts and every that fit on the tailshaft. Then you would only need the crossover gear and bearing. It's a good idea to install a new stake nut as well.
A lower 1st gear, and the ranges in second and third gear You will roll through soft sand much better,
sand suck's with a 3 speed, with a 4 speed also a lot more comfortable IMHO as DD your remember your top end will not change if you use your original 3 speed t case you will have a 17% lower gear in low range. also consider a small body lift EZ to do, about 3/8"to 1/2" thing will be very tight other wise
sand suck's with a 3 speed, with a 4 speed also a lot more comfortable IMHO as DD your remember your top end will not change if you use your original 3 speed t case you will have a 17% lower gear in low range. also consider a small body lift EZ to do, about 3/8"to 1/2" thing will be very tight other wise
Do you have a 3 speed tcase? I am looking for one. I have a 4 speed I am swapping for a sm420. Smelling a trade here
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- #10
Well first thing I need to do is my homework and learn all the terms in relationship to the parts you cats are talking about. I have a 3 speed vacuum transfer case. And this might be on hold for now, I have an electrical gremlin. And it only got worse after a nameless shop here mucked things up.
No... I pull the tranny by lowering the back of the engine, I don't even take the tranny cover off some day I weld on some removable bolt on flanges ...maybe
You will be glad you did the swap. If your not going to do any serious wheeling try to get a complete 4 speed tranny with the transfer case attached. I would highly recomend keeping the 3 speed case if your planning on wheeling alot. The lower ratio is a huge difference on the trail. Whatever you decide I would go ahead and replace the clutch no matter what. Much easier just to do it now since you'll have it all pulled apart anyway. I would also recomend having the flywheel "turned". If you have the cash I would also go to the 4 speed clutch/ flywheel. There are more options for the newer style clutch.
Check your bell housing, If you have a 2f you might already have the right bell housing.
Check your bell housing, If you have a 2f you might already have the right bell housing.
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- #13
I agree on that, I will probably do the clutch while it's exposed. I don't plan on much 4 wheeling. Just gotta build some funds up. There's a 4spd on Craigslist for $150. But which 4 sped is a better route to go? So if I understand it correctly. I can use my 3 spd transfer case and with some other parts it can marry with a 4 spd trans. So than I don't have to mod my drive shafts or do I?
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H42 4 speed is the most common and road able, The H41 has a granny 1st gear ,
since the 4 speed is longer than the 3 speed some drive shaft mods are needed later years you can just find some 4 speed drive shafts and swap them in
since the 4 speed is longer than the 3 speed some drive shaft mods are needed later years you can just find some 4 speed drive shafts and swap them in
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- #15
Ok gotcha, so I replace the drive shafts with later model shafts. That makes sense and what about my 3spd transfer-case? Is it easier to adapt it to the 4 speed or try to find a 4spd combo already together? And I read somewhere to be sure the 4 spd isn't from anything later than a 8/80 because of spline changes. Does that sound right? But I think my engine is 2f from the 1982 time frame. So maybe I have a bell housing that's older?
Yes the splines have to match so early H42,and what ever axle flange pattern early or later and what ever works for you $$, I think the H42+ adapter kit IMHO
It is much easier to put a 4-speed transfer case on a 4-speed transmission (IMNSHO).
You CAN put a 3-speed transfer case on a 4-speed transmission, and has been done many times. You'd need the right input gear and some bearing (part numbers posted in many threads) and probably some fancy shimming to make it work.
The easiest 3-speed transfer case to a 4-speed transmission is the late F "Transition case" that came behind the 1.5 F in 1974. That transfer case looks just like a 3-speed and holds the 3-speed gears (which you would have to source) without the fancy shimming inside. It's a lot of work for a small improvement in crawl ratio.
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- #18
Ok, then 4 spd all the way around. I am cool with that. Different drive shafts and probably do the clutch while the booger is opened up. Guess I need to see what kind of bell housing I have and go from there.
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- #20
Alright I am going to revive this thread. So far I have pieced to together these parts
4 speed tranmission=not sure if its a h41 or h42
4 speed bellhousing
4 speed flywheel and clutch
Correct "gear" to mate 3 spd case with 4 spd tranny
I still need:
drive shafts
slave cylinder
bolts for mating the two pieces
Some bearing that keeps getting mentioned
Shims?
Now I am a little bit in the dark here about transfer-cases. I have the vacuum shift 4wd 3 spd t-case. Since I am not 4 wheeling and this is my DD should I try finding a 4 speed transfer case? And removing my vacuum shift and just add a second hole in the floor for the hi-lo shifter? I want to find the easiest way to make this transition. And can you help with with these pics? Which transmission is this? I know its a 4 speed but is this the right direction for compatibility?
4 speed tranmission=not sure if its a h41 or h42
4 speed bellhousing
4 speed flywheel and clutch
Correct "gear" to mate 3 spd case with 4 spd tranny
I still need:
drive shafts
slave cylinder
bolts for mating the two pieces
Some bearing that keeps getting mentioned
Shims?
Now I am a little bit in the dark here about transfer-cases. I have the vacuum shift 4wd 3 spd t-case. Since I am not 4 wheeling and this is my DD should I try finding a 4 speed transfer case? And removing my vacuum shift and just add a second hole in the floor for the hi-lo shifter? I want to find the easiest way to make this transition. And can you help with with these pics? Which transmission is this? I know its a 4 speed but is this the right direction for compatibility?