Behemoth D300 Apex

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woody

woody

eternal noobie
Staff member
Joined
Oct 12, 2010
Messages
1,955
Age
58
Location
Toquerville UT
Finally tired of the MMW issues...I had that case as dialed as I could, but losing a set screw and eating a few intermediate gear teeth at the end of 2024 left me with additional headaches. Decided the special offered by Behemoth for their new cast aluminum Dana 300 Apex case was a deal worth taking.

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Simply, I swapped everything over, and upgraded to their new 32-spline front shaft too.

Weights (with oil and linkages) are nearly identical
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First impressions (two days, 4ish hours)

I've forever been unable to shift from 4 to two when loaded on the trailer....the MMW and the D300 stocker before took some solid hokey pokey to permit the rear to shift into neutral. The Apex does this easily, and has 4 times straight. Coincidence? Time will tell...

Shifting used to be rear/low with my MMW, and now it's normal D300 forward/low linkage. Gonna take a bit of getting used to.

The MMW was clocked about 5 degrees. Because of the shift mechanism on the Apex, it's now 10 degrees. Still 1/2" off my skid plate. I also re-worked my already modified passenger seat rail for clearance.

Shift linkage is nearly identical in design, even reused the old 3/8" shift rods, just had to tweak the bends to clear the seat and give room for my hand on the rear steer switch.
 
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oh yeah, my stock D300 had a little annoying "chatter" in high when running the dunes. The MMW had a LOT of chatter. The Apex has a tiny bit, but seems to run dramatically quieter...
 
SteerAndStuff said:
Was curious the fitment with the shift mechanism on top and clearing the seat.
Click to expand...
Simply, cut the 1" tube out of the seat, and replaced with a trimmed piece of 1/2" angle. Then wrapped the vinyl "inside" of the tube. Zero change to how the seat "sits" and no change to the seat feels since the suspension ties into the upper bolster tube.. Wish I had done this with the prior case instead of cutting/bending the tubes.
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Dumb (smart) things that Behemoth did....

A vent spot on top of the case, rather than relying on the rear output vent location. I always had a drool from that vent. The higher/more forward vent should help prevent that.

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Next, two threaded holes on the rear cover at the outside edges. These line up with the alignment pins on the main case body, and once you have ALL the 3/8 allen screws removed, you can use two of them to push the back half off. SO smart. (NOTE: remove the lock tab for the intermediate crosspin AND use a brass drift to keep this crosspin IN the main case...gentle taps as you tighten the two screws)

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Finally, mounting spots front and rear, top and bottom for linkages or other uses. I used two for my shift setup

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Stuff Behemoth provides for install that I didn't use...

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6 threaded studs with washers and nylocks...the studs are the good ones with an Allen to install, but too long for my adapter.

They provide two brass 3/8 NPT plugs, plugs, plus one steel/square and another for a vent. I prefer just the brass ones, and have never understood why you need a 3/8 hose for a vent, so I did my own thing.

I also changed out some of their 1/4" cap screws for button heads (clearance and consistent with what I already have installed) and trimmed the "outer" ends off the outside shifting cams. Clearance is tight, so I trimmed everything I could. Probably saved a quarter pound in weight too :p
 
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I blew our dana 300 gears out last year ay wolf caves. Started to build a new buggy. Took a chance and ordered their 4 speed case. When it was delivered the shaft that holds the nut for the rear yoke broke off as soon as i set it on the trans jack. Call the 4x4 shop and told them what happed. They contacted Behemoth and talked to them. Since the 4x4 shop had ordered and received 4 cases besides ours. They came our replaced the shaft in all the cases. They even came to my garage and did mine. I did not have to take to them. Apparently they used a different company to harden the output shafts because the one they normally use was backed up. I would say that is good customer service. I am glad to hear that it shifts easier than the dana 300. ours was finnicky sometimes lol. We are hopping to have the new buggy done in a few months and looking forward to seeing how the new setup works. I also ordered their cable shifters.
 
So is the Behemoth case still smaller than an Atlas?

It'll be interesting to see how that shift mechanism works long term. I know stock D300 are old, and the MMW parts weren't made correctly, so they all have issues shifting.
 
Stock D300: 16" wide and 8" tall

MMW300: 16-1/2" wide and 8-1/2" tall

Apex300: ~17" wide and 9-7/8" tall including linkage heims (case alone is 8-3/8. Width should be close, harder to measure in the car) I believe their billet machined case is a tad smaller.

Length for all 3 is identical. The back of the Behemoth has nothing protruding other than the bearing plate for the input (well, and the rear output, doh), I now have space for a power sports battery low in the chassis.

Just loaded on the trailer, AGAIN shifted into rear neutral with zero arguments. Hope to get into some more "bound/shift" situations this aft and see how it performs.

From the internets, the Atlas II is 17.5" wide and 9.79" tall.
 
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Tools and things...

Allen wrenches: 5/16, 7/32, 3/16, 5/32, 3/32. The 3/32 is what's used for the set screw that captures the flat head stock screw for the cam/shift arms connection

NOTE: only the front output side shift arm needs to be removed for assembly. The input/rear output shift arm does NOT need to be removed, BUT you need to "install" the round D300 shift ring, AND the gear prior to slipping the input assembly into place. There are allen screws top/bottom for the thru-rod that the shift arm pivots on. Those allen screws are buried in Loktite Blue....so get a small pick and clean them before removing. I put the flat head stock screw in dry, then "soaked" the hole for the tiny set screw with Blue. I hope that's right :)

I like Indian Head Shellac for the input assembly and the front output shim plate. Really, it could be used on the other spots too, but I used a bit of Gear Lube Gasket Maker on those.

The rear output opening includes an o-ring recess. I smeared a bit of Gear Lube Gasket maker on that mount surface. (o-ring is included)

Permatex 54540 got used for any NPT fittings. Gear Lube Gasket Maker for any set-screw allens.

Max Flex is what I like for the trans/case/adapter mating surfaces.

AS ALWAYS: let your sealants cure for 24 hours before adding fluids....leaks suck, and being in a rush is usually the cause.

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Pics from assembly:


See those holes in the cam above the shift arm? That's where those tiny Blue-buried set screws reside...

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Front linkage stays in place, set the slide collar into the link arm, then the input gear, THEN fit the input housing/shaft, and LAST the snap ring.

The brass shift blocks have R stamp on them...Weird I know, but those are directional....and you should be able to read the R on all 4 of them when rotated correctly. (R means facing to the REAR....I know, obvious....but.....)

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Indianhead Shellac.

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Set the Intermediate gear into position, then fit the crosspin. THEN the shims/bearings. Rotate the assembly as the HALF the pins get dropped, then the middle shim, then the other half. It IS work counting those pins...I got lucky, but....lol

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Fit the front input, then the slide collar and the shift arm. The thru-case rod gets installed, set screws with some Gear Lube Gasket goop, and finally, the shift screw and tiny baby locking set screw.

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More:


This should be obvious....

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O-ring recess:

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And the O-ring with some Gear Lube Gasket maker schmeared on it...

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Intermediate pin, tapped a bit too far....so....

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....so I can schmear Gear Lube Gasket maker on that opening, then push the pin thru to seal it.

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Great write up Woody!!!!!! I to got an Apex while they were on sale. Sadly I haven't made time to put mine together yet. So I'll be re reading and asking some questions when the time comes.
 
Had mine out wheeling again today, I HAVE been able to bind the shifting, but when a rear tire is smushed under a ledge, that's expected. So far, very pleased with the shifting (tho, I'm still getting used to forward/low...lol)
 
I guess this is what I wasn’t understanding the other day I didn’t realize why you got the behemoth because I could have sworn you already had a billet case but now it makes more sense
 
The 32-spline front output requires specific parts - the bearing/seal are included, and I already had the star washer, yoke, nut, etc. Notes for future reference...
  • bearing: NTN 30207
  • seal: National 473454
  • rubber star yoke washer: Chrysler #4210973
 
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