Mud truck gearing

Fellas, this is good info. I do know that I was surprised that the 39.5's hook as hard as they do. I don't have near enough engine to turn mine the way they should be turned. I need more engine and hopefully that will come this winter. I just can't decide the route to get there. Chris

pipedobber wrote:Fellas, this is good info. I do know that I was surprised that the 39.5's hook as hard as they do. I don't have near enough engine to turn mine the way they should be turned. I need more engine and hopefully that will come this winter. I just can't decide the route to get there. Chris

I know exactly what you mean. I have 3 bogs on my new engine, and I'm already thinking about changing everything this winter. I really want a forged stock stroke screamer.

I was thinking of a high comp. stock stroke, high rpm deal, but now I'm leaning more towards a 4.3 stroke deal. I'm thinking that maybe a torquier motor will allow me to pull through all three gears versus trying to keep my rpm's way up. Schmitty and Kris, do you have more input on this? Not trying to hijack this thread, just good reading and info. Thanks, Chris

Im running a 10.8:1 mafia head 521 with a hydraulic Ford Racing A443 cam. It makes amazing torque and doesnt need to spin to the sky.

I can definately see Im leaving a ton of horsepower on the table but Im glad I took baby steps in to this new motor. Its crazy how much more bottom end the 521 made vs the 460. I run in the high 4s low 5s now with a less than optimum suspension and a few trans gremlins.

I dont see 700hp and mid 4s being much of a problem with a new cam and a few tweaks even on pump gas.

I can attest that Kris' truck is bad ass, but still think the gearing needs to be re-worked some to keep it straight and make it faster! I have less motor in my ranger and less gear to keep the tires spinning faster. Right now I run a 3.55/4.10 setup, it's a little steep and makes steering impossible while staging if the front is locked it, but when it's in the hole on soft mud, the fronts spin much faster keeping the front end up and straight letting the back end do the work in pushing the truck through the hole. I run different tire classes so it's not always at the optimum rpm range, but it does spin to 6000 in all of my classes. I run 4 33x12.5 boggers in "A" class, 35x10.5 front and 35x15 rear boggers in "B" class, and 4 38.5x11 boggers in "C" and "D" classes. When I run the "X" class I leave the 38.5x11's on the front and put a set of cut 39.5 boggers in the rear. Granted the truck only weighs 3018 with me in it on 38's, but it hooks so hard with my suspension setup that the front tires almost come off the ground when I launch at 3200 on the cuts!

I leave the line in 4lo on a 205 in 1st gear, shifting at about 15' in the hole when it's about to hit the rev limiter, and stay in 2nd where it's just under 6000 for the rest of the hole. My converter sucks (3500 stall) and I am almost overpowering it when I launch, so that me par tof my problem.

Long story short, it takes a ton of variables to get your mud truck to run right. Track conditions and type of track, gear, tire size, converter, tranny, motor, and suspension, they all play a part and need to be looked at to make your truck run the way you think it should.

How many of you run lockers or welded fronts this will cause you to go crooked if you really hook the truck. This is caused by chassis flex applying more pressure to your right front tire than your left front tire causing it to bite the track harder pulling the truck to the right. I run 38.5x 11 on the back and r-85 buckshots on the front with one gearset highr front to rear (for example 3.50 front/3.70 rear) this is to spint the fronts a little faster but more to compensate for the shorter tire in front. Also I tryed to run 38.5x15 tires on the back and they dont hook as good as the little tires(on fast tracks that have bite) on sloppy soupy slick tracks they seemed to do a litttle better. The narrow tires have more pounds per square inch on them than a larger tire allowing it to bite harder.

Im running a detroit in the front. I know its part of my problem.

38.5x15 boggers have the narrowest lug spacing of any bogger out there which is why they dont hook as good.

Kris, you sure about that? My 38.5x11's hook pretty hard on both my 150 and my ranger. You've seen the150, for a 200k 351w, that thing is faster than it really should be. And it tracks pretty straight through the entire pit.

I have never run any type of locker or pos in the front of my truck after seeing a friend hit a wall because he welded his front up. When he was able to keep it off the wall he also went slower with the welded front.

38.5x15wide boggers have the narrowest lug spacing but its extremely close to the new 54" ones. The 38.5x11s are much wider and 39.5x18s have the widest lug spacing.

All boggers arent uniform in their lug spacing.

Im not going to deny its harder to hold with all 4 digging. Im not quite sure why it would be slower.


Just ask Karl how hard it is to keep my truck straight. He had my truck sideways in the pit back in March. Fun times.

I didn't know you had the detroit in the front. Pull that thing out and put an open back in before you come up in October. I can almost guarantee it'll track straight then! I know that when I pulled the welded front back out of my 150, my speed went up and my times got lower. So think about that, slow boy....

eeeeehhhh

Just for reference, here is me driving Kris' truck with him videoing it from inside the cab. I think iscared him so much he dropped the camera...

good times.....


I dont think this website is ready for presurized homemade wine bongs.

I believe the reason a truck will speed up is you are going staighter so you have less distance to cover and I think you free up a few more ponies for the back tires to move you thru the pit. As i have found out over the years the back tires should do 80%-90% of the work the fronts are more just to clear the way somewhat for the rears on a speed pit bogs are a complete different animal. I tried for years to keep all four tires pulling thinking it would make me quicker when i tossed that theory and tried the weight tranfer method I speed up tremendously.

I cant post links since i am at work but if you go to youtube and search for TODD DRAKE you will find several videos of my truck typically I run 125 ft fast tracks in 2.3 to 2.6 seconds.

How do you think 3.50's in the front-4.11 in the rear with 35x10.5 boggers will work?

Works great for me!

"How do you think 3.50's in the front-4.11 in the rear with 35x10.5 boggers will work?"

Personallly I think this is to much split especially if you are running the same size tires front and rear. It will cause more binding in the driveline causing it to eat u-joints and possibly transfer cases. I would look at 3.50frnt/3.70Rear or 3.70 frnt/4.11 rear if I were you.

True that if you are running the same size tire, the closer offest is easier on driveline parts if the surface you run on is kind of stiff, like a sand drag. But in full out mud, as long as you don't go more than 60% offset (like the 3.50/4.10) then you are safe. I've been running that setup in my ranger with chromoly shafts front and rear on a D44/31sp 9" combo. I have broken 1 shaft when I slammed the driver side into the wall. If the u-joint hadn't grenaded I believe it would have held up.

I run in 4 different tire classes and 1 cut tire class. And to be honest, I have been rethinking my whole gearing setup. I found that on 38.5 boggers with the 1.96:1 low range of the NP205, 1.46:1 2nd gear of the c6, and a rear gear of 4.10, if I spin the motor to 6800rpm, I only will get a 66.4mph, but if I run in high range and switch to a rear gear of 5.13, then I can get a wheel speed of 104mph. In the game where wheel speed is key to making a faster running truck, this simple swap is looking better all the time. Here's the calculator I use if you want to put in your info:

http://www.4lo.com/calc/gearratio.htm

kjett wrote:

I run in 4 different tire classes and 1 cut tire class. And to be honest, I have been rethinking my whole gearing setup. I found that on 38.5 boggers with the 1.96:1 low range of the NP205, 1.46:1 2nd gear of the c6, and a rear gear of 4.10, if I spin the motor to 6800rpm, I only will get a 66.4mph, but if I run in high range and switch to a rear gear of 5.13, then I can get a wheel speed of 104mph. In the game where wheel speed is key to making a faster running truck, this simple swap is looking better all the time.

What does it do when you shift to 3rd? Meaning, Does it lug down or something? Reason I ask is because now I'm thinking about running a 4.10/4.56 with 38's. But IF my motor won't pull 3rd. to 6k I'll be disappointed. I'm guessing we are probably close on HP and TQ.

I don't know how it's gonna run yet in high range. I'm gonna go the gear swaps this winter.

Just an FYI for you guys I tried several gear combos this year and I will say there is a point that if you gear to high and the truck starts spinning you cant get the truck moving as it wont bite( I slowed down around 2.5 tenths when I got to this point), Also if you go to low the truck actts if it hooks really hard and you are spinning the heck out of the engine but wheel speed is so low that again you go slower. I will not divulge my gear combo online as to much of the compitition might be watching but this is a very fine line here. Also when you look at your gear combo take everything into effect tranny gears, transfer gears, and differential gears. With a standard c-6 and a 205 transfer switching from low lock to high lock is basically the same as taking off in 2nd low range.

kjett wrote:I don't know how it's gonna run yet in high range. I'm gonna go the gear swaps this winter.

I may have misunderstood your earlier post. I thought you were saying you ran it to 6800 for 66.4 mph, in second gear. I was asking what the engine did when you went to 3rd. Still in lowside.