2F SM420 swap to H42 (1 Viewer)

[Elpaka]

My 77 Fj45 has an SM420 transmission and I've bought a H42 to swap back into it as the 420 is in bad shape. Does anyone have insight on modifications that would have been done to get the Chevy trans in there? Or could the h42 be bolted back it into the housing and go from there?

Thanks in advance!

 

[cult45]

Pics mate. Pics or it's mostly conjecture.

 

[4Cruisers]

IIRC, the SM420 bolts up to a 3-speed bellhousing, so you'll need a 4-speed bellhousing at a minimum.

Other info here, Post #10:

crawl ratio

 

[Cruiserdrew]

You will need a 2F Bellhousing. I think the clutch fork will likely work.

You may need a new slave cylinder depending how it was set up.

You'll need to see what linkage you have.

You will need a "4 speed" transfercase, if you still have the one out of your 77 that's perfect.

SM420s rarely go bad. What's worng with it?

 

[Rock40]

Uh, yeah. What IS wrong with it? The SM420 is a fine transmission and it is very easy to rebuild. It has a HUGE 1st/reverse gear that you'll be missing with the H42. It'd be much easier for you to rebuild the SM420 you currently have then to source all the parts you'll need to swap back to a Toyota transmission. I just sourced a rebuild kit for my "spare" SM420 and it ran me $115. The parts were quality too, exactly what you get from Novak only 1/2 the price.

 

[franken60]

..helping with this swap.
The sm420 currently does not stay in 2ND or 3rd. 3rd doesn't even feel like a gear anymore, just slops around as if there's nothing there. 2ND will violently kick out of gear no matter how hard you try to keep it in going downhill.

It's a great trans in theory, but for a daily driver in town it's essentially useless. the h42 has a much nicer range of gears for hopping around town.

We're looking to get this on the road by early, mid April and rebuilding seems like a poor way to go.

New Parts we have:
H42 trans in good shape w/ shifters and linkage
transfer case
Bell housing
Trans Mount
Flywheel
Clutch
Pressure plate
Clutch fork
All the bolts for reassembly

 

[pb4ugo]

Yep, When SM420 starts popping out of 2nd, usually they're done.

FYI, if you gotta good 420 that stays in 2nd, never allow it to grind going into 2nd.

 

[franken60]

It grinds in 2ND when you go to out it in at a stop. Not even moving...

 

[BC40]

Sounds like you have most parts covered.
What adaptor was used to install the sm420? If a plate adapter then driveshafts may still work, though front one likely would have a smaller 3spd yoke on it to clear the sm420. Might have to mix and match there. If it was an AA style extension housing then different driveshafts definitely needed.

 

[franken60]

Sounds like you have most parts covered.
What adaptor was used to install the sm420? If a plate adapter then driveshafts may still work, though front one likely would have a smaller 3spd yoke on it to clear the sm420. Might have to mix and match there. If it was an AA style extension housing then different driveshafts definitely needed.

Not sure on the housing, but the transfer case is a stock cruiser case by the looks of it. With an adapter plate