Planetary Info - Copied From Fabrication Board

Christian Riedel

Well-Known Member
« Thread started on: Jan 3rd, 2007, 7:12pm by [SIZE=-1]Randy[/SIZE] » [SIZE=-1]
[/SIZE] Could we put together an info list on planetarys: average cost, strength, weight, ratio, where to find them, when they were in production, equipment they were used on, and maybe which ones are easer/harder to find.
Clark, Pettibone, ZF, PS115, Hurth, and so on.
Also how about some pics?
Thanks guys,


Christian Riedel

Well-Known Member
« Reply #1 on: Jan 3rd, 2007, 7:27pm by [SIZE=-1]MTUJeeper [/SIZE]» [SIZE=-1]
[/SIZE] Randy, you read my mind. I thought to start a thread like that last night/this morning about 3 am, but decided sleep was more important.

Christian Riedel

Well-Known Member
« Reply #2 on: Jan 3rd, 2007, 7:35pm by Randy»
Good minds think alike

I`m trying to decide what kind of planetary to use, and I thought this would be helpful to me and hopefully others.

Christian Riedel

Well-Known Member
« Reply #3 on: Jan 3rd, 2007, 8:29pm by Brian Allen » [SIZE=-1]
[/SIZE] Randy,I know most teams run Clarks especially with a rockwell F-106 housing because their more [email protected] dependable but Rockwell PS-115's are lighter and their are teams that still run that planetary because they like it or they can't find anything else.I know Randy Moore from War Wizard has some Rockwells for sale go to his site at and click on the for sale gallery.

Christian Riedel

Well-Known Member
« Reply #4 on: Jan 3rd, 2007, 8:41pm by MTUJeeper » [SIZE=-1]
[/SIZE] Well, I'll post this up so scott doesn't have to type it again. I was asking him about pettibone planetaries which I am planning on running.

"Concerning Pettibones, for the price and what the current state
of the Industry is (Show business) I think they are one of the better
buys in terms of components. This "Sport" isn't really a sport....yet.
Like I said earlier, it's show business. You work with promoters to get
bookings and you negotiate you fee with them ahead of time so your
performance at the event isn't directly tied to your pay. You basically
set your fee based on your reputation and popularity with the fans. If
you're known for being a good performer, you and ask for a higher fee,
if your somewhat unknown or new or kind of a dark horse, then promoters
aren't going to be willing to pay as much for you. They basically get
one or two "big stars", maybe a couple of other "popular" trucks within
the industry and the rest of the field is filler. Now none of this has
much to do with what planetary you run other than I mention it to make a
point. When you're starting out in this business, the most important
trait you need to portray is reliability. There's already plenty of
folks that run mega hard and thrash their equipment to be the big star.
So promoters have plenty of those to choose from. What they need is
good reliable operations where the team is professional and the
equipment will last the entire show. Promoters don't care much whether
you win or loose, they basically want you up and running at the end of
the show just as you were at the beginning.

Now that is not to say that you should drive super conservative
and not push the equipment because you do need to put on a good show.
But the focus should be on constructing reliable equipment that can take
the abuse that the Industry currently demands of it so that you can push
it and learn it's limits without having chronic reliability issues. In
my opinion the Pettibone is one of the best components for the price
weight and reliability considering what shows are like today.

Now, more specifically, what makes them different than other
planetaries? First let's look at the outside. Overall, they are about
the same size as most other "big" planetaries, they are basically
somewhere between a PS-115 and Clark 20 ton in size and in weight.
Also, they have 12 wheel studs versus 10 that are found on Clarks so
that's better wheel retention, very important when the wheel and tire
combo is basically the size and weight of a grizzly bear. Also, as you
may have noticed the wheel flange is in the middle of the hub instead of
at the inboard edge. Thus the wheel flange is further outboard allowing
the wheel center to be placed closer to the middle of the wheel, which
in turn, makes the wheel stronger. Also having such a less hub
protruding through the wheel center makes it incredibly easier to mount
and dismount (Especially dismount the wheels in tiring up and down.

Moving internally, the Pettibone is much different than other
planetaries used in Monster Trucks. With your background, I will assume
you are familiar with a planetary gear set so I won't risk insulting
your intelligence with a lengthy explanation on how they work. Rather I
will explain the differences between the Pettibone and others. On every
other planetary hub that I have seen used on an MT, the sun gear is
attached to the end of the axle shaft, with the planet gears revolving
around the sun gear but attached to a drive plate, which in turn, is
attached to the end of the hub. The ring gear is a stationary piece,
inside the hub, that splines onto the spindle. Thus, as the axle shaft
spins, the sun gear also spins. The sun gear propels the planet gears
around the ring gear and as they revolve around, the drive plate that
the planet gears are mounted to, rotate the hub and wheel. The gear
ratio of the planetary is the combined ratio that is the product of the
ratio between the sun and planet gears and the ratio between the planet
gears and the ring gear. Also, since the ring gear is stationary, the
planet gears revolve the same direction as the sun gear and axle shaft.
Thus the hub spins the same direction as the axle shaft.

In the Pettibone planetary, the sun gear is attached to the end
of the axle shaft just like others, but from there it's opposite of what
other planetaries are like. The planet gears are attached to a
stationary carrier, inside the hub, that splines onto the spindle. And
the ring gear is actually incorporated into the hub itself. So, the
axle shaft and sun gear spins one direction and that spins the planet
gears the opposite direction. Since the planet gears are held
stationary and the ring rotates with the hub, the hub is spun the
opposite direction of the sun gear and axle shaft. So basically,
Pettibones reverse the rotation of the axle shaft. Like other
planetaries the overall reduction of the hub is the product of the ratio
between the sun and planet gears and the ratio between the planet gears
and the ring gear. Because the Pettibone planetary reverses rotation,
they may make it easier to layout the drivelines in certain chassis

Other internal differences include the Pettibones having four
planet gears instead of just three found in most other types (Some ZF's
have four planet gears too). This spreads the torque over four gears
instead of just three which improves reliability. Also, I have been
told the Pettibones have larger spindles than the Clark 20 ton. Indeed,
I have NEVER seen a Pettibone spindle fail and I've watch Dan Evans
abuse his tremendously.

Additionally, Pettibones are more readily available. It is
getting harder and harder to get Clarks and parts for them as the
Industry eats up the remaining ones left, they are no longer in
production. However the Pettibone, which is found on a large variety of
equipment, is both common in industrial salvage yards and still in
production. This makes it much easier to acquire parts for them and
they are cheaper both in initial cost and in parts than Clarks.

Those are the basic differences between the Pettibones and other
planetaries and essentially my reasons for going with them. They are,
by far, not the lightest and if I were to design a planetary from
scratch for MT's there would be allot of things I would do different.
But for someone starting out on a limited budget, such as myself, and
for what is currently being asked of teams and equipment I feel they are
the best buy going and will go along way towards creating good overall

Great, soon people will all start wanting these and the price will skyrocket by the time I get around to picking a set up...thats my luck, lol.


Christian Riedel

Well-Known Member
« Reply #5 on: Jan 4th, 2007, 01:05am by Brian Allen» [SIZE=-1]
[/SIZE] Thanks for the information and I agree whole heartedly!!!!!I'm not really that familiar with the Pettibones and because they have 12 lug bolt pattern makes it hard for me to discern between them and a Rockwell PS-115.As far as it being show business in my opinion ever since they started racing these things it's been a sport but when its promoted as a 2 truck show and every body else is just there to get beat is when the sport becomes devalued and can not be taken serious by the fans,media,and the rest of the motorsports world.In the big picture it is show business whether your racing in NHRA,Nascar,Indycar or Unlimited hydroplanes and whether or not your paid a purse or a flat rate, but I'm a racer and I'm out their to win whatever there is or isn't to win and the fans remember who wins and it has to be very hard for those guys to put their blood @ guts into their trucks @ make the sacrifices from their families and what successes they have no one knows very much about.What is great about this sport is that their are so many promoters or sanctioning bodies you have the opportunity to work with unlike other sports that just has one main sanctioning body but it is needed in this sport because it's so saturated.Again,whats going to separate you @ your truck from being just another face in the crowd?Thanks Christian!

Christian Riedel

Well-Known Member
« Reply #6 on: Jan 4th, 2007, 10:20am by MTUJeeper » [SIZE=-1]
[/SIZE] Don't thank me, I didn't know any of that, that is all from scott bryant (Sinister '32), I appreciate him writing all that. Christian

Christian Riedel

Well-Known Member
« Reply #7 on: Jan 4th, 2007, 10:29am by Sinister '32 » [SIZE=-1]
[/SIZE] I should also add that the Pettibone has a much thicker wheel flange (Where the wheel studs attach to) than any other planetary I have seen. There's been at least a couple of instances where the wheel flange has broken off of a Clark hub.


Christian Riedel

Well-Known Member
« Reply #8 on: Jan 4th, 2007, 2:46pm by MTUJeeper » [SIZE=-1]
[/SIZE] Okay, I found an animation to make it easier to visualize. If you look at the middle of this page, by pressing the first button, that is an animation of the clark and others style. The last one is an animation of the pettibone style.

Christian Riedel

Well-Known Member
« Reply #9 on: Jan 4th, 2007, 4:11pm by Sinister '32 » [SIZE=-1]
[/SIZE] Take note of the ratio formulas on that page! Put them somewhere handy for reference so you can calculate ratios when you are out scrounging for parts. Christian, I think this page is a good candidate for the Resourse/Knowledge section! Good find!

Also, this team's website has some great shots of Pettibone planetaries as well as an animation of them too!

Ruff Time Website

Christian Riedel

Well-Known Member
« Reply #10 on: Jan 5th, 2007, 4:10pm by Overkill» [SIZE=-1]
[/SIZE] There are a number of planetaries which have been re-tasked for use in the monster truck industry. Most of these are decades old designs scavenged from obsolete construction equipment. However this may eventually change. Contemporary planetary axle designs offer superior engineering and materials as well as greater gear reduction.

To my knowledge the first planetary to find it’s way onto a monster truck was the Rockwell PS250. These were first mated to 5 Ton Rockwell military axles in 1984 on a little known monster truck named the ‘Texas Armadillo’.

In this early example the PS250 hubs were actually mated to the 5 ton spindles as opposed to the subsequent use of flanges to mate the planetary ends to the desired axle housings.

Monster truck owners soon realized the performance advantage when planetaries found their way onto high profile trucks such as Bearfoot and Bigfoot. PS250s are found with both one piece and two piece knuckles, some on flanged champagne cups and others on fixed housings.

As planetaries became a standard component of a monster truck cost and availability became a major concern. At that time the most readily available planetary was found to be the Clark 20 Ton. As a result nearly 20 years later this has become the industry standard. In addition to being plentiful these were also long considered to be bombproof. That is until recent years. Today these have become scares and weaknesses have surfaced. Axle shafts have been a weak link when used in combination with Rockwell F106s. This is due in part to the Clark’s roughly 3.5:1 reduction. In addition new weaknesses have been found such as spindles and even drive flanges!

Another planetary which found it’s way onto monster trucks very early in the game was the Rockwell PS115. These first appeared on Fred Shafer’s Lil’ Bearfoot in 1984. I personally favored the PS115 due to its greater 4.3:1 reduction and relative light weight (as compared to the PS250 and Clark 20 ton).

Though these have high strength champaign cups the weak point is the knuckles themselves. We found a way to sufficiently strengthen these but today David Smith of King Krunch has developed billet steel knuckles which have eliminated this weakness. It is also my understanding that he has found a 5:1 gear set which is a direct replacement. Unfortunately the PS115 too has become hard to locate.

Now the lesser known planetaries.....Mixed in with Rockwell and Clark planetaries was the sporadic use of the Pettibone planetary already discussed by Scott Bryant. (See earlier post)

Arguably the largest planetaries to ever find their way onto a monster truck were incorporated by Jeff Dane on his Awesome Kong II. These massive planetaries he claims were salvaged from a 170 ton Navy beach recovery vehicle. These were so large in fact that they just fit within the 32" diameter wheels of his Goodyear 73" tires.

A little noticed planetary in use today is the Gallion. These compact planetary ends have been quietly used for years (and very successfully I might add) by Dennis Anderson on his Grave Digger trucks. One advantage of this planetary is that it can be adapted to a standard Clark 20 ton knuckle. These are also lighter than the standard Clark 20 ton hub. However once again the draw back is their availability.

Here is another variation of the Clark which was brought to my attention by Paul Winkleman (Evolution & American Thunder monster trucks). These are actually an aluminum version of the Clark 20 ton planetary. It is my understanding that these hubs will also mate directly to standard Clark 20 ton spindles and knuckles. However I am not aware of anyone who has tried to run these on a monster truck as of yet.

Now the mighty minis....

Few monster truck components have been so coveted as the ZF APL365. Though there were a few issues which had to be worked though, who could not be impressed by their spectacular performance. These small planetaries were first implemented (pun intended) by Jack Willman back in 1989 on his Taurus Racer due to their light weight. There were however several other benefits. First and foremost these feature a 6:1 gear reduction. Secondly they are of a very compact design which reduces leverage on the spindles, knuckles and king pins. As a result these have proven to be extraordinarily strong. The weakest point of these was their spindle nut which was prone to stripping. Tom Meets at the wheel of Paul Shafer’s Monster Patrol and later his own trucks (Maximum Destruction, Hot Wheels, etc.) has beaten these to a pulp and appears to have addressed every potential weakness. If these planetaries were actually readily available they would surely be the standard.

Other similar ZF axles have been and are used by a few teams. Fred Shafer (Bearfoot) received a sponsorship from ZF back in 1991 which allowed him to obtain very rare APL 735s. Later Bob Chandler secured the ZF sponsorship for his Bigfoot team but chose the larger APL 755 with integral wet brakes. Predictably these are also very scarce.

The latest mini to glean interest is the Clark/Hurth. As I mentioned earlier these were first utilized by Alan Pezo on his Predator race truck back circa 1994. However he experienced reliability issues with the axle housings. In recent years Jimmy Creten experimented with the Clark/Hurth on his wife’s Scarlet Bandit truck. Kirk Dabney is also running complete Clark/Hurth axles under his latest Overkill truck.

Mac Plecker has also been successfully running the Clark/Hurth on sheet metal axle housings with custom built knuckles and Ford 9" centers for over a year now. These axles were built by Matt Heady as prototypes for his incredibly light Big Gun monster truck. His truck features chromoly axle housings with billet aluminum knuckles and billet aluminum hubs with Clark/Hurth spindles and planetary gears. I believe this is the most extreme example of planetary axles to date. Though Clark/Hurth planetary axles are uncommon it is my understanding that replacement parts can still be ordered over the counter.

There is a common thread which runs though this entire post. It is the lack of availability of these re-tasked tractor parts. As the supply is expended builders will need to resort to other means to keep the industry going. Custom built sheet metal housings such as those offered by Dan Patrick are now replacing the Rockwell F106 housings used for over the last decade.

Pablo Huffaker (Grave Digger, Blacksmith) now offers custom billet spindles, David Smith offers custom billet knuckles, SCS offer custom inner and outer axle shafts, and Matt Heady single handedly fabricated s billet aluminum version of a production planetary. Therefor, how far off could we really be from purpose built monster truck planetary axles? I believe the industry has been inadvertently inching towards this for some time. If a concerted (combined) effort was placed into the vision of a standardized planetary axle (though the biggest hurdle will be agreement on the specifications) and I am confident that this could (and will) be accomplished in the foreseeable future.

Marty G.
Overkill Racing

Christian Riedel

Well-Known Member
« Reply #11 on: Jan 5th, 2007, 4:42pm by Sinister '32 » [SIZE=-1]
[/SIZE] Outstanding Post!!! I would be more than willing to be part of that combined effort

Christian Riedel

Well-Known Member
« Reply #12 on: Jan 5th, 2007, 7:13pm by MTUJeeper » [SIZE=-1]
[/SIZE] As always marty, you have outdone yourself. I don't know what we would do without guys as knowledgeable as you and scott. Just going out on a whim the other day I put out a part request. I got a call back from a guy who sold Tom Meents a set of APL-365s earlier this year, or last. He quoted me 5k per axle. While a steep price, the lack of failure you see with these compared to the standard f106s is almost worth it in the long run. Christian

Christian Riedel

Well-Known Member
« Reply #14 on: Jan 9th, 2007, 11:28am by Sinister '32 » [SIZE=-1]
[/SIZE] Those are Clarks on Predator. They have been modified to accept a Rockwell bolt pattern (12 lug instead of Clark 10 lug). Allen did that because he had a set of rims that were Rockwell pattern and it was easier to modify the hub than the rim.

I believe those hubs on Dominator are just regular Clarks with the end plates painted silver.


Christian Riedel

Well-Known Member
« Reply #15 on: Jan 9th, 2007, 11:45pm by TRex » [SIZE=-1]
[/SIZE] We'll have to ask Kyle on that one, but I'd bet a good sized steak dinner that those are Pettibones of some model!! Chad

Christian Riedel

Well-Known Member
« Reply #16 on: Jan 10th, 2007, 10:45am by Sinister '32 » [SIZE=-1]
[/SIZE] on Jan 9th, 2007, 11:45pm, TRex wrote:[FONT=Arial,Helvetica]We'll have to ask Kyle on that one, but I'd bet a good sized steak dinner that those are Pettibones of some model!! Chad [/FONT]
Chad, I think you're right, I stand corrected. They are 12 lug. But they are not the "pie pan" style. They are most likely the re-badged Rockwell PS-250's that some Pettibone equipment has. Below is a shot of the hubs that Prime Time, now D'sturbed runs. They look the same as what's on Dominator and I believe these are the Rockwell PS-250's even though they say Pettibone on the face plate. I've seen hubs like this on some of the older Bigfoot trucks too, and they all ran PS-250's


Christian Riedel

Well-Known Member
« Reply #17 on: Feb 20th, 2007, 10:43pm by [SIZE=-1]LEE [/SIZE]» [SIZE=-1]
[/SIZE] Just wonder what model galion did the planetarys came out of and part numbers are? Plus will they fit on SCS Clark knuckles?

Christian Riedel

Well-Known Member
« Reply #18 on: Jul 21st, 2007, 1:38pm by Kyle »

Hey guys. Have to say great thread and thanks for starting it!!! Being a person that plans in the future of building a monster truck this tech info is great !!! I have a question I found some planetary hubs I assume them to be the 20ton Clarks but after reading this article I seem to think they are the Galion type take a look and see what you guys think:

If they are the Galions does anyone have any info on them? are they a good buy?