Builds Early Fj40 Rock Crawler Gets a Refresh (1 Viewer)

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Thanks for your input. Parts availability should not be too big of an issue because I am pretty positive any noises I hear are bearing related. Also nice to hear a press isn't essential. I did not find rebuilding my transfer case to be hard, so I am not too scared to dive into this trans. I'm really just looking for other things to trouble shoot before I tear it down.
Hopefully this weekend my dad will have some free time and can pop the transmission tunnel off and check the top cover situation. If that is not the issue, then at least I can get a head start on sourcing parts or getting some quotes from a shop to rebuild it. I still have a goal of being able to wheel it this summer but a busy schedule and lack of funds are making that quite the mission.
No problem. If you've got the time and patience, I'd recommend you take on the rebuild yourself. Paying a shop will be fairly cost prohibitive.

I will say that the bearings in the SM420 and SM465 are extremely robust and I've never personally seen a failed one assuming they have lubrication. HOWEVER I have seen a 1st/reverse gear with significant damage on the hub surface. It's not a syncro (because they're not synchronized on 1st/reverse) and I don't have my manual in front of me unfortunately. Essentially it's a hub "cone" and on the later year transmissions (which you think yo have) GM switched from bronze to some sort of aluminum compound which didn't hold up nearly as well. It can gall, seize and get very sticky. When I've rebuilt later year models, I've used the older assembly with the better bronze parts.

It's possible this could be your issue. I can send attach some parts of the damaged part later if you'd like. It's on my wall of shame
 
No problem. If you've got the time and patience, I'd recommend you take on the rebuild yourself. Paying a shop will be fairly cost prohibitive.

I will say that the bearings in the SM420 and SM465 are extremely robust and I've never personally seen a failed one assuming they have lubrication. HOWEVER I have seen a 1st/reverse gear with significant damage on the hub surface. It's not a syncro (because they're not synchronized on 1st/reverse) and I don't have my manual in front of me unfortunately. Essentially it's a hub "cone" and on the later year transmissions (which you think yo have) GM switched from bronze to some sort of aluminum compound which didn't hold up nearly as well. It can gall, seize and get very sticky. When I've rebuilt later year models, I've used the older assembly with the better bronze parts.

It's possible this could be your issue. I can send attach some parts of the damaged part later if you'd like. It's on my wall of shame
I have the patience for a rebuild, just not a lot of time unfortunately. 1st and Reverse is where I seem to have the issue of it really locking up so maybe that part is part of the issue that I am having. By locking up I mean to get it out of gear, I need to release clutch and inch forward to pop out of gear into neutral, or really slam the shifter back (Which I do not like to do obviously). I am really hoping its just an issue with my shift rails or top cover. If it is not I will gladly take on rebuilding this transmission myself. In the 5 years I've been driving, a transmission is the only thing I haven't had to rebuild so it makes sense to me that I might have to dive into this. I just write these off as learning experiences and luckily my parents aren't concerned about me lowering the property value by always having disassembled trucks laying around.
 
So the transmission is on the ground, top cover off. The internals look very very clean. I can’t see any issues with the clutch either. What should I specifically be looking for inside this thing. Shift rails seem to be in decent shape. I do notice a good clunk when I move the reverse shift head. The gear appears to be interfering with something. I don’t know if that would cause the issues I’m having. I’m going to be tinkering and researching throughout the day. Hopefully something jumps out at me or someone can give me a good suggestion because I don’t want to blindly throw cash at this transmission.
 
So the transmission is on the ground, top cover off. The internals look very very clean. I can’t see any issues with the clutch either. What should I specifically be looking for inside this thing. Shift rails seem to be in decent shape. I do notice a good clunk when I move the reverse shift head. The gear appears to be interfering with something. I don’t know if that would cause the issues I’m having. I’m going to be tinkering and researching throughout the day. Hopefully something jumps out at me or someone can give me a good suggestion because I don’t want to blindly throw cash at this transmission.

Let me know what you find. I have a similar issue with my SM420 getting stuck in 2nd gear (3rd if you’re counting granny gear as 1st). I have to start pulling on the shifter a few seconds before I’m ready to shift to hopefully get it to “slot” it’s way out so when I depress the clutch it will come out of gear. If I don’t do that or if there’s a load on the transmission (going uphill) it’ll get stuck for sure.

Worst scenario I’ve had is trying to get onto the main road and it stuck in 2nd. Had to pull over and shift into low range and then convince it to work it’s way out.
 
No progress so far on the cruiser which is kind of depressing for me but it's not like I haven't been busy. Besides not having a shop or concrete to work on, the central California heat doesn't help motivate me to get outside and work. My next move is to get this trans back up into place and replace all of my clutch related hydraulics. Hopefully that cures my weird binding issues. I have very little experience with transmissions but the inside of this sm420 looks pretty mint. Along with advice on this forum, as well as some fb groups, my issue is most likely something with the mc/slave or a combo of the two.
I likely wont be able to work on the cruiser until mid August. Ill be doing a 10 day section hike on the John Muir Trail so that is taking up a few weekends. Hopefully the trans/clutch issue ends up being simple so I can get this thing moving and start doing some real work on it.
I scored a set of 37" km2's for cheap and some 17 inch pro comp wheels as well. This should help out the road manners. 60+ mph on 11 year old bias iroks can get a little crazy.
 
No pics worth posting but updates on the 40.

I took quite the break from working on the 40 as I had a big hiking trip coming up. I've spent my life in the outdoors and camping but never backpacked before this. I went a lot bigger than your average first timer. I met up with some friends who were doing the John Muir Trail and hiked about 100 miles with them. Immediately after returning, I spent a weekend in August trying to figure out my binding issue that I have been fighting. I replaced all the hydraulics and nothing changed. Then the next realization was that on steep inclines my drive line could possibly be binding just enough to restrict movement. Not the case either. With a new clutch, master cylinder, and a slave cylinder, my binding issue has to be somewhere in the transmission or transfer case.

I lean towards transmission because there is for sure bearing noise when in neutral with the engine spinning the goes away when the clutch pedal is depressed. The transfer case remains a variable though because I did reuse the old input gear during my rebuild last summer and there were a few small chips. I'm thinking those small gear chips may have become big chips and under load they are causing a bind. I ended up deciding my next move needs to be trans and transfer case tear down to figure out whats not spinning. Took it out and set it on a bench so I could save some funds. Well then the Creek Fire started. Luckily my family is not in direct danger but the pre evac warnings came within a few miles of the house so I ran home to help prep a bit in case the fire made a run. Part of the prep was getting the cruiser mobile to limp it out just in case.

My next move is to just save up and throw some cash at this setup. I do not want to find a new trans because I'm not ready to re do all of the associated mounts that come with a trans swap. I thought about finding a new sm420 but even that I am not interested in as I have no idea how this one off adapter is set up and I'd rather rebuild my existing trans than swap parts to a used one or NOS.

I want to do t/c and trans at same time. I want this all done at once and I want it done right so I am not taking this out again in a year. I am leaning towards going with the Orion case because stock 3 speed gear sets are hard to find and pricey. The other thing I like about the Orion is I will have the gearing that I learned to love in my dual cased pickup.
 
It used to be that when an sm420 wore out you could replace it for $100.00 I love sm420's so I have collected a few. I have had a couple wear out over the years and just retired them. Given the age of that transmission you could potentially throw a bunch of money into it and not get any good results. I don't think it matters how the one off adapter is setup, it is a fairly easy to connect an sm420 to a 3 spd. case. If it was me, I'd find another one and throw it in.
 
It used to be that when an sm420 wore out you could replace it for $100.00 I love sm420's so I have collected a few. I have had a couple wear out over the years and just retired them. Given the age of that transmission you could potentially throw a bunch of money into it and not get any good results. I don't think it matters how the one off adapter is setup, it is a fairly easy to connect an sm420 to a 3 spd. case. If it was me, I'd find another one and throw it in.
I've been considering swapping in another one but for a few bucks more it seems I can just get mine professionally rebuilt which might be the route I end up going with. If a killer deal comes along I will probably snag a used one though.
 
How much more work is it to swap in a 465? They seem to be much more plentiful and all around a better transmission? Excuse any ignorance..
 
How much more work is it to swap in a 465? They seem to be much more plentiful and all around a better transmission? Excuse any ignorance..
To be honest I don't know and that was going to be part of my research today. I do know it is a bit longer and a new adapter would be longer than my current one, which would force me to re do my driveshafts as well as all of my mounts. I really did not have any issue driving the sm420 around so I don't have a huge desire to upgrade. Even if I did find a great deal on a 465, I'd have to get new adapters, re do my mounts, etc... In my quick search on craigslist I already found a few 465's in my area which shows this could be a decent option. Right now I am just in the research stage of all of this until the wildfire smoke goes away and working outside isn't as miserable.
 
Personally, I like sm420's better. The adapter setup is very close to the same on both, with the exception of the output shaft.The sm465 needs to be drilled out and tapped for a bolt to retain the input gear of the t-case. The sm420 is tapped from the factory. Not that big of a deal, I just find the 420 is a bit smaller a bit lighter and a bit better #1 gear ratio. They are both very tough trannies.
 
Personally, I like sm420's better. The adapter setup is very close to the same on both, with the exception of the output shaft.The sm465 needs to be drilled out and tapped for a bolt to retain the input gear of the t-case. The sm420 is tapped from the factory. Not that big of a deal, I just find the 420 is a bit smaller a bit lighter and a bit better #1 gear ratio. They are both very tough trannies.
I am heavily leaning towards keeping the sm420 that I currently have. Local shops have given me good quotes on a rebuild and the idea of having a fresh 420 for not much more than a craigslist find is appealing.
 
The point I was making about re-building is the fact that they are so old, when components wear out to the point that the transmission starts to jam up, there could be parts inside that are worn beyond repair. The cost to replace these parts will outweigh the cost of a used one that shifts correctly, not to mention mixing old and new parts in a gearbox is sometimes questionable. I think most of the old timers who know that transmission well are mostly dead. That being said, I hope you have good luck rebuilding and your transmission works well afterward.
 
Ok so pictures will come later today when I send them to my laptop, but I have finally made some progress on the cruiser. I'm kicking myself for putting it off and now I have to wrench in the heat but the spring skiing was surprisingly good for such a terrible winter and I just couldn't stop going. School was also taking up some time, but not as much as the skiing.

I rebuilt the SM420. I had called some shops to get some quotes, and while the prices were fair I just couldn't pull the trigger to have someone else do it. I figured a transmission as simple as this would be a good learning experience so I decided to dive in. I went with the Novak kit and while there were no super obvious "gotcha" moments to explain my ongoing transmission issues, I got it back together and it works so I managed to fix something. The bearings were obviously shot when compared to the new ones so I'm going to assume that is where my issue was. The synchros all looked great as well but I was not too worried about that as my issue was with 1st and reversed which are not synchronized anyway. There's still a lot of noise driving around but I've heard that is just a part of these things and I am sure the chipped up gears in my transfer case are not helping either.

With the cruiser drivable for the first time in over a year I moved to the little things to get this thing to actually drive "comfortably" down the road. Or at least somewhat straight. After years of being beat on and then parked for almost 10 years, every piece of rubber in the suspension was either missing or failing, and half of the body mounts had disintegrated. I'm going to guess my death wobble was the result of neither front shackles having any bushing left. Maybe it is because I am only used to driving beater trucks but I am shocked at how well this thing drove at 60+ with bias plys and non existent bushings in the front end.

I began replacing all the front bushings and freshening up the leaf spring packs with new plastic isolators. I don't know why I anticipated this to be the easy part. I had to kill all of my hardware with either a bfh, fire, a cutoff wheel, or combo of all 3. The good news is it is apart now but I wish I wasn't so naïve and would have ordered all new hardware before I started. All that is in the mail now and hopefully this next weekend I can finish the suspension bushings and body mounts so I can drive the cruiser to a friends house to weld up my center console. With that installed I can finally finish my wiring and get rid of the rats nest of loose wiring laying in the cab right right now.

I'm really itching to get going ASAP because I've always been the one friend in my friend group that has off-road toys but now one is almost done with his ranger prerunner, another with his 4500 koh toyota, and a third just picked up a '42 willys. If I can get my s*** together, this summer should be full of fun times in the Sierras. Plus the old timers in town like seeing young people in old trucks and those interactions make it seem a bit more worth it since most people my age think spending money to drive over a pile of rocks is stupid.
 
Here are the few pics I took of the process.
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The inside of the trans was very clean. I knew this already as I had the top cover off previously but completely drained and in good lighting it is even easier to see.

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The SM420 is a pretty simple unit.

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Back together and ready to go.

I am also still curious if anybody else has seen another M&M Engineering adapter out there. I cannot find any mention of it anywhere on the internet.
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The lifesaver of this part of the project is my friend who let me use his welding table to work on this. Much better than a folding plastic table in the dirt that I would have had to use at my parents house. He has a pretty sweet project going on too.

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Long Travel ranger with a 5.3 swap. All of the fab work has been done by him, totally self taught. It sits on its own weight now but a lot more work to be done.
 
So I have neglected the thread for awhile now but the cruiser has not received the same treatment. Since I rebuilt the sm420 in the summer of '21 I have put tons of miles on this thing and have had a great time driving it and wheeling locally. I've decided to update the thread because I am going to be doing some Rubithon prep. This will be my first trip on the rubicon.

Before I get to prep I'll cover what I have been up to since '21. Fought same transmission issue that I tried solving with the rebuild but decided to just deal with it and drive it.
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Spent the summer wheeling around on some mild local trails and escaping the heat of the Central Valley.

Winter '22 I bought a 3 speed case in order to swap gear sets because I had chipped teeth on some of the gears and I assumed that was what was causing t-case noise as well as some of my binding issues. Turned out not to be the case so I continued ignoring the problem and kept driving it as much as possible.

Into '23 now, I added some lighting, no Yokohamas, and reinstalled the bumper with a rebuilt 8274 to prep for King of the Hammers. Trailered down and had an amazing time bouncing around out in the desert with friends.

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