HumboldtEF's GCM Racing CMAX FJ40 build

[HumboldtEF]

I'm considering a bit of a refresh on this thing since there's one thing thats never been great, the drop transfer case. Sure its super scale but the skid protecting it (or the transfer case itself) really holds the truck back. Its a low rig so its gonna drag, getting hung up or pivoting on the skid just makes for a painful drive. Going down obstacles it likes to get caught on the skid and pivot 90 degrees, slide then roll on its side. A flat belly to drag would be much better.



So I think I may pick up the SSD Scale tranny from the Trail King to replace the GCM racing drop transfer case tranny.

I think this could really liven up this thing. It has great traction in the rear once it loads up the suspension. To be able to also drag the skid without getting hung up would be a huge help.

It would also be nice to get a better gear ratio since the GCM racing tranny is on the fast side.

[Big Bill]

Nice job on your truck really came out great looking. I did a Trail Finder a few years back, I went with a modified 3 leaf setup that worked OK after a lot of trial and error really fun trucks to play with. I lived up in your area from 2010 thru 2015( Hydesville) and loved all of the great places to crawl, Rohner Park behind the Rodeo grounds in Fortuna was my favorite. Your early photos in this thread reminded me of that area, I always thought a Scaler type event up in your area would be awesome.

[HumboldtEF]

Originally Posted by Big Bill

Nice job on your truck really came out great looking. I did a Trail Finder a few years back, I went with a modified 3 leaf setup that worked OK after a lot of trial and error really fun trucks to play with. I lived up in your area from 2010 thru 2015( Hydesville) and loved all of the great places to crawl, Rohner Park behind the Rodeo grounds in Fortuna was my favorite. Your early photos in this thread reminded me of that area, I always thought a Scaler type event up in your area would be awesome.

Hey thanks, If you can accept that Leaf sprung rigs are just different they really are fun and this one has a surprising amount of grip. Thats part of the reason I'm trying to eliminate the hump on the underside of the truck so I can get back to having fun.

I havent been out to the Rohner park area for quite some time. Maybe I'll check it out next time I'm close by.

I picked up and assembled the SSD scale tranny last week. compared to the aluminum tranny from GCM racing its 4oz lighter which is nice but it might upset the front to rear balance I had worked so hard on. Oh well I can always play around with some ballast if needed.

Heres the GCM tranny at 15.6 OZ


I woke up Saturday and realized I had never compared the SSD tranny to the GCM tranny. Turns out the SSD tranny is a left drop (driver side) but I need a right, its also too wide to be centered in the Cmax frame rails (it would need to sit at an angle).
So to get 2 birds stoned at once I worked up a new transfer case that gives me the right drop and squeezes the gears closer together so I can center everything in the frame rails.


I got the first prototype printed last night.




I got the orientation wrong on one of the mounts so its upside down, I need to fix that tonight. I also need to check the tolerances for the bearings and gear mesh, though I did mimic the stock spacing so mesh should be good so long as my measurements were accurate.

One more thing worth noting on the SSD scale tranny, I slotted the hole in the motor plate that provides clearance for the bearing bulge on the motor. I wanted to gear down a little more than it allowed (13T). As it comes the adjustment slots for setting mesh can only utilize half of the adjustment, this really depends on which motor you have and how large the bearing bulge is.
First I hit it with a abrasive dremel bit which was pretty terrible and sloppy then I remembered I had a round file which was way more effective and precise. Using the right tool for the job really helps.

I probably only needed to extend it a few millimeters but I took off even more so I wouldn't have to go back to remove more material.

[HumboldtEF]

I got the gear mesh too loose on the last print but fixed up a new one today. Its hard for me to precisely measure the center of a 10mm hole. My first attempt was measuring the outside walls of 2 holes and working backwards with some math to get to the distance between them, obviously that didnt work too well.
I was thinking I could print up a few shafts with a point on the ends or crosshairs, insert these into the original housing and then measure. Anyway I think I got it good for now so I'll save that idea for the next one.

I printed the new housing in urban grey which is a pretty good match for the SSD gray plastic.



One thing i didn't photograph was with the 3 screws that mount the front half of the T case and how 1 interferes with the bearing of the middle gear. My plan is to find a button head screw which should allow me to grind the head down enough to clear the bearing while keeping the hex end intact (because its a 1.5mm instead of socket heads 2mm)
I may also be able to get away with using just 2 screws but I'm going to try to use 3 first.

EDIT: this was the end result, a button head with a flat spot filed into it.


Another factor for how compact I could make this was the distance from the tranny housing to the driveshaft. my first design didnt account for this and they were too close.

Now with this version theres about 1.5mm to spare for the driveshaft to the tranny.

[HumboldtEF]

The new Transfer Case seems to be doing the job and I can now center everything. I'm fine tuning the skid now.







The motor and tranny now sit a bit lower and I had to yet again cut down the oil filter for clearance, I'm sure it will do fine



The incision driveshafts I picked up needed to be shortened in the front. I cut 8mm off each end, they still have plenty of engagement.

[clockwork]

Damn. Nice. Build. My current project is a FJ40 so this build thread made back to the top just in time for you to inspire me once again. Thanks.

[HumboldtEF]

This morning I lashed everything together, I had to clearance the body a bit for the new tranny but got it to a point I was happy with it. I swapped out the short helper leafs for some mediums. The battery tray also needed to be modified, I notch it to clear the driveshaft. I Added a few chunks of styrene to lift up the battery 4mm then I ran a thin sheet of 0.5 mm over it.



Then I took it out for a shakedown at the beach and man is it a welcome improvement! Its quieter, slower (which I was hoping for) and the flat skid can be easily dragged
The longer leafs I added worked out good too, I expected them to be too stiff but they felt good and added a tiny bit more ground clearance.


Before


After




One thing that in need to remedy is the body fitment, when I put the body on the wiring, battery or something is just barely clearing making it tricky to get fully seated.


Now I need to re-position the battery, electronics and re-do the wire management.

Originally Posted by clockwork

Damn. Nice. Build. My current project is a FJ40 so this build thread made back to the top just in time for you to inspire me once again. Thanks.

Nice! Do you have a build thread?

[rockhugger]

Originally Posted by HumboldtEF

One thing i didn't photograph was with the 3 screws that mount the front half of the T case and how 1 interferes with the bearing of the middle gear. My plan is to find a button head screw which should allow me to grind the head down enough to clear the bearing while keeping the hex end intact (because its a 1.5mm instead of socket heads 2mm)
I may also be able to get away with using just 2 screws but I'm going to try to use 3 first.

EDIT: this was the end result, a button head with a flat spot filed into it.

This looks great. Can you use flat heads instead of button heads, then you wouldn't have to grind anything down.

[JatoTheRipper]

Nice work on the transfer case! Very cool.

I love these FJ40's especially with those wheels and hubcaps.

[CODYBOY]

Very nice Casey, hope to see these rig at PBTF. Your design skills are killing it!!!

Ernie

[HumboldtEF]

Originally Posted by rockhugger

This looks great. Can you use flat heads instead of button heads, then you wouldn't have to grind anything down.

Thanks Paul

Thats a great idea too, I think theres just enough thickness in that spot to do that, though I think I'm lacking the m2.5 flat heads.

Originally Posted by JatoTheRipper

Nice work on the transfer case! Very cool.

I love these FJ40's especially with those wheels and hubcaps.

Thanks Jato, I've got 2 other sets of wheels that fit this rig but ever since I got the boom racing wheels I've rarely swapped them out because they just fit so well.

Originally Posted by CODYBOY

Very nice Casey, hope to see these rig at PBTF. Your design skills are killing it!!!

Ernie

Thanks Ernie, now that I've done these mods it will be coming to PBTF for sure

[Timmahh]

Aye. I was looking for a Mirrored image of the SSD Transfer case that would fit. You're correct. That would work pretty well for what I want to do.

However, I was able to mod the stock setup to work. its not perfect ofcourse, the case is now upside down, but it fits and will work. Just need to mod the chassis plate a little more. Problaby open the bottom of it to let the transfer case drop a little lower, as well as the bottom of the case, which is not on the top, at about a 18* angle. so I can make a mount to secure it to the chassis. A mirrors case snugged up to fit would be a great option for sure for those of us like you, that want to run a right drop case.

I set mine at an angle to be scale to the 1:1 Blazers. So maybe 2 sets of mounting holes, one for 90% and one for maybe 110ish* for the Chevy users.
Any who. The mods I did turned out to be pretty easy. At least on the plastic case form the kit. If the Aluminum case is the same, then this mod would not be to hard to do on it, and would be rock solid as it is now on my modded tranny/tfrcase.

But Love this. This is why I want to get a 3D Printer myself. 100's of ideas flowing.

[HumboldtEF]

Very cool! I look forward to seeing what you work up. I looked briefly at flipping the T-case housing but wasn't sure how to go about it nicely.

Here's a link for anyone curious to see what Timmahh is working on Building a TK Leafer SWB for RC4WD Blazer