Transmission Basics 101 - w/ second gear mod

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Savaged
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Transmission Basics 101 - w/ second gear mod

Post by Savaged » Mon Jun 16, 2003 9:10 pm

With the explosion of newly or soon to be released Monster Big Block engines ( or even MoldyMarvins custom fabricated dual big block axle twister 8O )- the drivetrain components of the Savage will be taking a huge beating. So far, the Savage drivetrain (minus the stock dogbones) has proven to be more than a match for the awesome HP/Torque numbers that these engines are putting out. In any case- beefing up the drivetrain internals is a good idea as a means of preventative maintenance, rather than waiting for it to break and possibly causing costlier damage. So far, HD dogbones, CVD's, and 4 spider gear diff mods have been the usual upgrades performed by most. But here's another one that's cheap and fairly easy (especially with the photo illustrations). On the other hand, it requires the complete removal and tear down of the transmission. So I wouldn't recommend doing this mod until the transmission is out of the truck for one reason or another (TVP upgrade, transmission maintenance kit installation, or perhaps even the 2 speed setscrew/screwshaft backing out). The mod simply requires the addition of a second screwshaft inside of the second gear drum. The screwshaft itself is the same one used in the transmission output drivecups (front and rear) that have been known to break causing you to have a front or rear wheel drive only Savage. This screwshaft inside of the second gear drum is what the 2 speed hub latches onto once the centrifical force inside of the hub is enough to overcome the spring pressure that dictates when 2nd gear is actually engaged. In stock form, the Savage tranny has only 1 screwshaft used for 2nd gear engagement. That means, when second gear kicks in (sometimes violently with high HP engines or in loose gravel with lots of wheel spin), the same screwshaft is absorbing the punishment over and over again each time 2nd gear locks on. Adding a second screwshaft will add a second shaft for the 2nd speed hub to latch onto therefore dividing the wear and the possiblillty of it's failure by 2. This can be beneficial to those running HIGH HP Super Mondo Big Block engines or those who plan on getting one. So lets get started.... The first thing to do is remove the transmission from the truck. See Picture 1:

Image

Being an automotive technician by trade- the terminology used to explain the internal parts of the Savage tranny is the same terminology used in full size 1:1 transaxles. I've labeled each part to help indicate which parts I'm referring to.

The second step is to split the transmission case open- you'll need to remove the transmission output drivecups, brake disc adapter, and brake disc.
See Picture 2:

Image

1st and 2nd gear are both riding on the mainshaft. 1st gear rides on a one-way clutch- which basically means, the clutch engages in one direction and releases in another. 2nd gear rides on the mainshaft on a sealed roller bearing. Both 1st and 2nd gear is being driven at the same time by the drive gears on the input shaft but since 1st gear has a 1 way clutch, the mainshaft is rotated by 1st gear only. To access the 2nd gear drum, the output shaft must first be removed to allow the mainshaft and all of it's gears to slide out of the case.
See Picture 3:

Image

When the truck is accellerating- first gear (being driven by the input shaft) grabs onto the mainshaft via the one-way clutch and rotates it at the 1st speed gear ratio (18/44). Although 2nd gear is also being driven by the input shaft, it is only rotating in place riding on its dedicated ball bearing. Once the mainshaft is spinning fast enough, the centrifical force inside of the 2nd gear hub (which is located inside of the 2nd gear drum) allows a cam lever to to overcome a user set spring pressure and pop out catching the screwshaft inside of the 2nd gear drum. 2nd gear is now driving the mainshaft VIA the cam lever on the 2nd speed hub and rotates the mainshaft at an even faster 2nd gear ratio (23/39). Since the mainshaft is turning faster than the 1st gear ratio- the one way clutch releases the mainshaft. The mainshaft drive gear (idler gear) is in constant mesh with the output shaft drive gear- the faster the mainshaft rotates, the faster the output shaft rotates. That's basically how the transmission operates and how it shifts from 1st to 2nd and from 2nd back down to 1st (if the mainshaft speed slows down where spring pressure is strong enough to push the cam lever back in, 2nd gear will be released and the the one way clutch (1st gear) will now be driving the mainshaft).

To access the 2nd gear drum- use a small flat blade screwdriver to pop out the retaining E clip on the end of the mainshaft. Slide out the drive gear (idler gear) and pin, slide out 1st gear (note theres a thin washer/shim between 2nd gear and the 1st gear one way clutch). Slide the mainshaft and 2nd speed hub out of the 2nd gear drum. All your left with is the 2nd gear drum in your hand. You should be able so see where the 2nd screwshaft can be installed- note that the screwshaft should be countersunk into the 2nd gear drum to avoid contact with the 1st gear one way clutch housing. (see your instruction manual)
See Picture 4 and 5

Image
Image

The shiftpoint adjustment in the transmission basically adjust how much spring pressure is applied to the cam lever. The more pressure that is applied (clockwise adjustment), the faster the mainshaft has to rotate to produce enough centrifical force to over come it to engage 2nd gear.

Follow the procedure in reverse for reassembly however, I'd recommend adding a dab of low grade removable Loctite (222) to all of the screws or screwshafts that thread into metal surfaces. With the transmission apart- now is a good time to clean off the one way clutch (which can often slip allowing the engine to rev without 1st gear engagement). Also, now is a good time to replace the original screwshaft in the 2nd gear drum and also the screw shaft that locks the 2nd speed hub onto the mainshaft (this is the one that often backs out- not allowing your Savage to roll backwards, and leaving you without a 2nd gear- It's especially critical to add a dab of loctite to this one!). Upgrades and/or repairs can be performed at this time to replace worn transmission output drive cups, install an alloy disc brake adapter, perform a dual disc modification, install the HB Titianium Output shaft or HPI lightweight input shaft drive gears. It's also a good time to look at the transmission internals to get familiar with how it works...

Have Fun!!

Savaged
Last edited by Savaged on Thu Aug 14, 2003 10:49 am, edited 5 times in total.
Mirrors only show how much more work needs to be done...

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rcmarty
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Post by rcmarty » Sat Jun 28, 2003 7:24 pm

I did this too. Shifting was much smoother - could hardly hear it.

I'm running a picco p5 marine engine with an aircooled head

I found that the shifting pawl hitting this new pin (and trying to go past due to power) took a chunk out of the plastic gear. Once the piece was broken out the shifting pawl would get stuck - locking it in second.

I can take a pic if anyone likes. It looks like the shift point adjusting hole is twice a s wide as it originally was.

Don't know if i got a weak gear , drive too hard , shift late in powerband.

but i thought i'd offer my experience as food for thought.


martin :)

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Post by Savaged » Sat Jun 28, 2003 10:29 pm

Thanks for the response and input... wow 480+ views and your the only one that had any input :? The screwshaft threads through the second gear drum and is supported by the metal plate on the other side... I'm not exactly sure what's happening to your tranny...are you starting to tear apart the inside of the second gear drum..?

Picture showing the second gear drum with both screwshafts installed. There's a metal plate (not shown) that supports the ends of the screw shafts that is secured to the drum by 2 small screws
Image

It should be impossible for the pawl to get past the screwshaft pins unless the engagement hub that holds the pawl is starting to wear out and the pawl is able move around a bit sideways when is swings out.

Pictures below borrowed from "MouldyMarvin's Project Twin" post
Image

Image

Also, remember when installing the screwshafts through the second gear drum, it should be slightly countersunk so that the end of the screwshaft pins enters the designated holes of the metal plate on the other side.

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Post by rcmarty » Sun Jun 29, 2003 12:03 am

I have some pics of the gear. Where do i put them so they will show up here ?

I liked the mod and the way it performs. Maby i got a bad gear.

I didn't countersink the bolt the first time (more flush) anyways i ended up machining :oops: a circle in the first gear. LOL

the shifting pawl pin that goes through the disk (3rd pic down) is worn oblong in shape now. Still works but looks like a work clutch shoe (flywheel pin stretching out hole).

I'm going to get a new shifting setup soon.

I need to work on the shock ends. I was out trashing tonight ans ripped open both shock ends on one corner.

Martin :)

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Post by Savaged » Sun Jun 29, 2003 12:18 am

I didn't countersink the bolt the first time (more flush) anyways i ended up machining a circle in the first gear. LOL


Yeah I made sure to mention that in my original post...cause I knew it'd happen to somebody...
Wow! If the pawl pin hole is oblong...it might just be due to normal wear and tear. (What kinda power is that marine engine putting out anyways?). You can buy tranny internals from TowerHobbies..

To post a picture, read this post. www.picturetrail.com and www.rcpics.com will host your pictures for a fee...

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Post by rcmarty » Sun Jun 29, 2003 12:33 am

I'm not sure what kind of power the picco puts out.
I know it was the hottest boat motor you could get 7-10 years ago. Picco booklet says 1.9 hp. Not alot of power but we run alot more nitro here than in italy. So maby the hp ratings are for 0% nitro. I'm running 20% traxxas top fuel.

My 21bb has been flowed (sharpen crank, flow down ports) GH cooling head and with the same setup (16t bell ) we have a site with a 50 degree hill 40' high i can get about 2-5' air at the top. I had the picco in there last week with a air leak in it (wicked bottom end lean no idle down for no-one) and on the same hill i got an easy 10' air at the top.

There's another savage i run with too and his 21bb doesn't have the power mine does. So my 21bb is a good one or the clean-up is adding power but the picco makes it look like an electric!

I'll check into the pic hosting. Can i host the pics at my webspace and link them to the site ? I have 10m of space included with my internet but i need to learn how to use it :)

Martin :)

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Post by Savaged » Sun Jun 29, 2003 1:26 am

Provided each picture has a seperate URL address, your webspace should work. Otherwise, you can send a link to one of your albums to we can look at the pictures individually...


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Post by mrowekamp » Sun Jun 29, 2003 6:14 am

You didn't mention, but i guess it would be wise to loctite those setscrew shafts?

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Post by Savaged » Sun Jun 29, 2003 1:12 pm

Right on! I could swear I mentioned it...but after rereading the post...i guess not :oops: I'll add it in now! Thanks... :wink:
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