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EK4-S2 w/2 Speed. May 25, 2002 OFNA Monster Pirate 2-Speed in the EK4.
After putting the OFNA Dominator MT3 wheels and tires on my EK4, I fell in love with the way it
handled and the fact that for the first time in a while, the clutch didn't get
hot and slip. The only real drawback to the lower profile tires and wheels was
the noticeable loss in top speed. I was already running the 18 tooth clutch bell
and wasn't able to find a larger clutch bell or a smaller spur gear that I knew
would bolt into the beast. I decided if I was going to have to modify something,
I might as well go all the way and do it right the first time. Two Speed - here
I come.
I called up my
favorite MP Toy store,
It took me a couple of days of working on it off and on to get it mounted and ready to go. I did have to strip the truck completely as I was swapping chassis, cleaning, inspecting and shimming my Diff gears and changing both servo's. I would estimate this to be app. a 4 hour mod if you didn't have to do all of the other things I did.
I'm going to do a really quick write
up here on what it took to convert the 2-speed into the EK4. If you are
considering doing this or something like it, please read the disclaimer first.
DISCLAIMER:
I have run app. 20 tanks of fuel through the 2-speed EK4 so far. About 6 of those tanks of fuel were beating the snot out of it on pavement. Some with the large stock tires as well. So, as far as longevity is concerned, be warned that I am not making any claims as to how long the two speed may withstand the torque of the Pro .70. My personal opinion is that it may hold up due to the much lower rpm's, (18,000) of the Pro .70. I'm guessing that the load may be comparable to say a 3+ h.p. RB-C4 shifting at 40,000 rpm's.
I
will be sure to update this immediately if I experience any problems. I will
also update the tanks run as I get the chance to run them. You may
want to wait until I get more run time in before doing this mod yourself. I am going
to do this page while my memory is still fresh. If it doesn't work out, we can
all look back at it and dream about what could have been.
Before we get started. This exact procedure will not work with the gears that come standard with the 2-speed. You would have to fabricate a custom top center spur support to use the larger gears as well as possibly have to cut out the chassis for clearance. The brake lever would be a real stinker if not almost impossible to hook up as well. The one advantage to using larger gears, (lower ratio) would be the possibility of eliminating the Big Gotcha. Parts Used. Click on the little picture to make it bigger.
The initial outlook. When I decided to give the 2-speed a try, I was thinking I would end up needing all of the MP center diff parts. I thought the only way that I might be able to do it was to mount the 2-speed just like it would go in the MP and then drill the EK4 chassis to mount the whole MP center diff in place. I was delightfully surprised to find that I could actually use all of my EK4 mounting parts with a few modifications. The MP 2-speed was so close to being a direct bolt in, it wasn't funny. Unfortunately, close isn't always good enough. The MP unit was app. 3/16th of an inch too long. I was able to make it work by first removing a small spacer from the 2-speed. I then had to move the rear diff mount towards the back of the truck the 1/8th of an inch I still needed to gain. The stock engine mounts happened to be in perfect alignment, (clutch bell to spur gears) with leaving the front diff mount in it's original position and moving the back diff mount the 1/8th of an inch. With the exception of the Big Gotcha, this was a very simple procedure that can be done with nothing more than the common tools everyone should have, including a Dremel Tool with a couple of different bits. While I could have used the milling machine and fabricated a new top diff support, I wanted to do my best to use only the tools that most people do or should own. Modifications required. I'm only going to write concerning the modifications and procedures required that vary from a stock remove and install of the center diff.
1.
The first thing to do is to remove the front drive collar from the new 2-speed
unit. It's the one with the flats on the outside of it for the brake discs.
2. Remove the bearing from the shaft behind the drive collar you just removed. 3. Remove the small 1/16th" aluminum spacer shown in Figure A. Note: click on any picture to enlarge it.
4. Replace the bearing and the drive collar. Make sure to use a drop of red loc-tite on the set screw in the drive collar. I remove it completely and place a drop into the threads as well as on the set screw. Works like a charm. 5. Remove the two large spur gears and replace them with the 48/52 gears. Make note that the larger gear goes toward the front in both instances. Also, make sure to use a drop of red loc-tite on the little screws that hold the gears. 6. The 2-speed should have come with a small chrome spring as well as a black one that is already installed. Mine came with the weaker, black spring installed. That is the one I chose to use and it seems to be fine. I did un-adjust the set screw some, a couple of turns) to make it shift early. The set screw that screws in on an angle is the adjustment for shift point. I haven't played with it at all since getting it running. I may turn it in to move the shift point up a little higher in the rev's, but I'm not sure that I'm not happy with it the way it is now. 7. You will need to use the Triple H top diff support. The stock Top Diff Support is not wide enough to be modified to clear the 52t gear and remain in one useable piece. 8. The Triple H piece needs to be modified in the following way. See Figure B. a. Remove the center bridge. b. Slot the two rear mounting holes. I used a Dremel with the fiberglass cutoff wheel to cut into the holes from the rear. c. Grind a little bit of material from the under side for clearance of the 52t gear. d. Remove a small portion just behind the brake cam hole.
9. For the brake lever, I used the
new one that comes with the 2-speed. It seemed a little heavier duty than the
original, but fit the hole in the brake cam perfectly. You can see how I
modified it pretty well in Figure C. They say a picture is worth a thousand
words. Good thing, It saves me a lot of typing.
10. This ones a little bit tricky, but it's not bad at all. You need to elongate the two countersunk holes in the chassis for the rear diff mount by 1/8th of an inch towards the rear. It's a bit tricky because you need to elongate the countersink as well as the hole. I used a small carbide cutter in the dremel, tipped on an angle to shape the countersink further back. If you don't do this, the screw will just twist forward as you tighten it. You could opt for a flat head screw in place of the tapered head if you wanted to. When you tighten these screws, try to hold the diff mount straight up and down while not allowing it to pull forward to it's original position. I know this isn't ideal, but it works and it's a whole lot easier than making a new custom chassis from scratch. Unfortunately, I didn't get any pictures of this. If you are having a hard time imagining what an elongated countersunk hole should look like, please send me an email and I will pull a screw and shoot a picture. 11. The clutch bell is fairly easy. You install the clutch bell before screwing the 12/16 gear onto it. Make sure you have at least a few clutch shims. I needed two thin ones and one thick one. Always try to shim the clutch from the outside to keep it as close to the clutch shoes as possible without any noticeable drag or rubbing. Once you have it shimmed properly, (least detectable amount of back and forth movement possible without having zero or no back and forth movement) put a dab of blue loc-tite on the screw and tighten it up. You can now screw the 12/16 gear onto the clutch bell. The MP guys over at RCMT usually just screw it on hand tight without any loc-tite. I followed there lead. The direction that the engine turns always tries to tighten it even further so theirs no need to wrench on it. 12. You will need to elongate the engine mounting slots in the chassis a small amount more toward the center of the truck. I use little bolts in place of the stock allen bolts that go there. I'm not sure if the stock bolts will be able to move far enough in the slot to allow proper clutch bell mesh/adjustment. If you need to get some different bolts with small washers, at least you won't be too surprised. The method we use to set the gear mesh is to fold a small piece of paper in half, (double thickness) and roll it in between the gears. Then hold in tight on the clutch bell, making sure the engine is straight in line or as close as possible to 90 degrees opposed to the spur gear. Then snug the bolts and pull the paper out. Make sure the spur turns freely all of the way around. Also, hold the spur and try rocking the clutch bell back and fourth to see if it has any movement between the gears. If it moves the tiniest bit, that's acceptable. The objective is really to get it as close as possible to having no detectable movement, while being sure it isn't in further than necessary to just remove the play. The BIG Gotcha.
UPDATE - With the New MSJ Engine Mounts - No modification is required to the engine. The inner MSJ mount only requires a little relief for the rear drive shaft.
13. Well, it's not really a gotcha. It's more of an I gotcha attention. I'm sure some people may steer clear of this mod after this one, but it's really not that bad.
I thought I was
home free and was amazed by how simple this install had gone. Then as I slid my
rear axle assembly into place with the drive shaft installed, I got a major wake
up call. Luckily I don't have a temper, so it just involved some very low keyed
curse words. At first I was thinking - No Way. This can't be happening to me.
Everything has gone so smooth and I was so sure I was home free. Well, I decided
I was too close to perfection to turn back now. I slid the axle into the
un-mounted rear end and the center diff. I then tried to slide the rear axle
into it's mounting position. When it stopped I got out the marker and drew a
line on the side of the engine and mount above and below the drive shaft. I then
got out the dremel with the carbide cutter and five minutes later I was home
free once again. I ended up going in until I just barely caught a tiny site of
the engine mounting screws. It works perfectly and has adequate clearance to
never rub or touch. Their ain't no stoppin us now, baby.
With the MSJ engine mount.
I wonder how my 3 year engine
warranty is holding up?
Here's some quick Gear Ratio's. Stock 14/60 = 4.29:1 18 Tooth 18/60 = 3.33:1 2-Speed 1st Gear 12/52 = 4.33:1 2nd Gear 16/48 = 3.00:1 Here's a few more pics.
And here's a video of the EK4 with a 2-Speed. Note: It is tuned very rich to better demonstrate the shift. With it tuned properly it blows through the shift so fast you could barely detect it in the video.
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