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ToddyBear
04-26-2010, 09:12 AM
- Have a 71' FJ40 SMC 350/SM420 mated to stock vacuum transfer. Clutch went, need to replace along with slave. The conversion is "custom," and not in a good way - old school home made. This is my sixth, Fj40, and it's a mess - wife bought it for my birthday. I guess I could use some advice before I dig into the fix.

First, do I attempt this in my garage, or do I find someone with some knowledge on FJ40s and conversions, more specifically "custom" conversions, etc., to take a look, and maybe do the work?

Second, since the clutch is in need of replacement, do I take this opportunity to replace the worn SM420 with an automatic, such as a 700r4, 4l60? Or maybe a NV4500?

Although I'm pretty handy, I don't have the tools to realign clutch, etc.

The little LC has driven a couple thousand miles without a hitch, pulled 1 1/4 ton military trailers all over the Colorado mountains, etc, and I've watch it just hang in there, with nothing more than a rear driveshaft rebuild, and couple gaskets. So, all in all, I'm okay with the mods, as they've done okay.

It also has a "custom" spring over axle conversion - a "custom" shackle reversal - a "custom" power steering conversion, and newer axles with front disk brakes.

Sorry for the lengthy thread - just weighing my options.

Thanks!

Todd

SteveH
04-26-2010, 10:59 AM
I suspect a shop won't want to mess with your custom conversion. I also suspect people on this list will know more than anyone else about identifying what you have and what small changes might make it work better. You don't need a fancy clutch alignment tool - just a socket extension and a set of eyeballs. It think a 700R4 swap will be a lot of work, too. I'd stick with what you have, given that it's fairly far from stock. Until you get it all apart, you may not really know how good/bad it is.

Uncle Ben
04-26-2010, 12:34 PM
700r4 and 4l60e are the same transmission with the difference being the 4l60e has an electronically controlled valve body. They are an outstanding auto with a decent first gear and of course overdrive. The flip side of that coin is they are looooonnnnnggggg! If your using a carbed 350, 700r4 is what you would go with. Installing a 700r4 in your set up will require a whole lot more work and fabrication that it sounds like you have time for or expertise in. A turbo 350 would be a much easier choice as they are much shorter. The NV4500 is a decent trans but very heavy and I suggest driving something that has one first as the gear splits are less than ideal. Your 420 set up is a common and dependable combination. Personally, I would fix what you have and enjoy it and begin researching your options for a later date!

Rezarf
04-26-2010, 06:11 PM
:thumb:700r4 and 4l60e are the same transmission with the difference being the 4l60e has an electronically controlled valve body. They are an outstanding auto with a decent first gear and of course overdrive. The flip side of that coin is they are looooonnnnnggggg! If your using a carbed 350, 700r4 is what you would go with. Installing a 700r4 in your set up will require a whole lot more work and fabrication that it sounds like you have time for or expertise in. A turbo 350 would be a much easier choice as they are much shorter. The NV4500 is a decent trans but very heavy and I suggest driving something that has one first as the gear splits are less than ideal. Your 420 set up is a common and dependable combination. Personally, I would fix what you have and enjoy it and begin researching your options for a later date!

Yeah, like you know what you are talking about :rolleyes: ;) :thumb:

UB, I learn something everytime you chime in.

ToddyBear
05-11-2010, 10:15 AM
Thanks guys! I'll take your advice and fix what I got [SIC]. I actually don't mind the gearing with the SM420 - fourth, with the 411s and 37s will cruise comfortably at around 80mph all day long. It's just a little worn, and when my wife drives it, it's a little much. I'll maybe check into the gearing when I have it down, I know there are rebuild kits for it.

Again, love this site - and appreciate your help more than you know.

Todd

Air Randy
05-11-2010, 11:49 AM
Dude, if you have an FJ40 that will "cruise comfortably at 80 all day long" then there isn't much that is wrong with it the way it is! It's a simple job to replace the clutch and slave cylinder, just fix that setup and stay with what you have.

SM420's are old style truck tranny's, they didn't shift very good or quickly when they were new, are you sure there is something wrong with it?

ToddyBear
05-13-2010, 11:59 AM
Randy - I've had six FJ40s, in different variances of custom - my first FJ40 was a 69' with the 3-speed, and it even shifted better! Actually, there really aren't any problems other than slow shifting - I run AMSOIL, so it helps. I'm doin the clutch this weekend - so I'm anxious to see if a fresh clutch will maybe bring about some easier shifting.

Thanks!

Todd

Air Randy
05-13-2010, 12:31 PM
I bet the new clutch & slave will help the shifting a bunch, especially if the old setup wasn't allowing complete clutch ddisengagement when shifting.

I'm sure the old 69 shifted better than the 420, that was my point, even an old Toyota OEM tranny shifts better than a 420 even on a good day.

Hope the repair works goes well, let us know how it turns out.

corsair23
05-13-2010, 01:25 PM
I'm doin the clutch this weekend - so I'm anxious to see if a fresh clutch will maybe bring about some easier shifting.

Interested in your results and feedback :thumb:

My SM420 has always shifted in a less than stellar fashion :rolleyes: - I just chalked it up to the fact that it is an old, clunky, truck tranny