Mud racing:

<font color=purple>Sandman, with your big heavy 'burb, you'll probably want to go to one extreme or the other with gears. With a 2:1 low (NP203) & a TH350, combined with 39.5's, I'd either go for 3.73's or 4.10's to run 1st gear, or drop all the way down to 5.13's & try to run 2nd. I've got a buddy with all one-ton stuff under his Blazer & a pretty hot 454 (.060 over, 12:1 compression, L88 cam). He's got 4.56's & can't quite turn 2nd gear in the thick stuff with 39.5's, but he screams like hell in first. In his case - and I suspect in yours as well - 4.56's end up being an "in-betweener" gear. He's got more motor than he can use in 1st gear & runs out of tire speed, but the engine doesn't have quite enough ummpff for such a heavy vehicle to run 2nd. You definitely won't want Boggers on the front & honestly on such a heavy vehicle, I'd probably skip 'em on the rear as well. Super Swampers will tend to pull you forward even as momentum bogs down where Boggers will dig straight for China.

Now, all this changes if you want to get serious about racing this sucker in relatively shallow mud. There, the tire of choice is the 38.5X11 Bogger at all 4 corners.</font color=purple>

TEX

[img]/wwwthreads_images/icons/wink.gif[/img] Got Mud?
G.U.M.B.O. Mud Racing

[The_Sandman_454]

What do you think of a manual valve body on the TH350? [img]/wwwthreads_images/icons/crazy.gif[/img] I still like the idea of shifting my own vehicle, but without the clutch, I can't see how I'd lose nearly as much momentum as I would if I had to use a clutch and move a shift mechanism... How would a manual valve body behave on the street? Would it work ok? How much power do you think that beast (your buddy's 454) puts out? 12:1 compression? Is it able to be ran on pump gas? What would 5.13's do to my final drive ratio, and more importantly, the speed of this thing on the road, and about what RPM? I'm not sure on the calculations, or I'd calculate the stuff... [img]/wwwthreads_images/icons/crazy.gif[/img]

About how light does the vehicle have to be to run Boggers? Something like the mini-truck, S10/little toyota size? [img]/wwwthreads_images/icons/crazy.gif[/img]

Just out of curiosity, has anyone ran swampers on sand? How'd they do? What size did you use? It's recommended to air the tires on sand down to at most 18psi, and generally 5-10 psi... I noticed from the interco website, that they are mainly 16.5" rims, and I heard those can't be aired down much or they'll break the bead, correct? [img]/wwwthreads_images/icons/crazy.gif[/img]

It's good to know the mud finally got it's own forum [img]/wwwthreads_images/icons/wink.gif[/img]

Tim
"The_Sandman_454"
[img]/wwwthreads_images/icons/cool.gif[/img] '79 Suburban 4x4 454, 6" lift, 35x12.5s & '85 GMC S15 4x4

<font color=purple>Yeah, a full manual valve body (and a ratchet shifter) is the way to go if you want to slap the shifter around. Stick shifts are strictly for playing around. If you want to race, you need an automatic - at least in the V-8 classes anyway. My pal's 454 is probably putting out around 550HP & runs on a mix of 93 & 108. He didn't really build the truck to race & it's pretty heavy. And now that it has a nice paint job, it stays clean most of the time. His motor is sort of a hand-me-down. His brother sold it to him when he built his 427, and that 427 is now in storage as that guy now runs a 488 (that's the S-10 I often mention). The 488 BTW is putting out nearly 800HP[img]/wwwthreads_images/icons/smile.gif[/img].

For Boggers in the deep, thick stuff I've noticed that as vehicles get much over 4,000 lbs, Boggers on the back become less effective & Boggers on the front are true performance killers. Definitely, over 5,000 lbs & I'd probably just run TSL's all the way around. Boggers just suck so my HP & they won't self clean at low speeds the way TSL's do. I know only two guys making good use out of Boggers at all 4 corners in deep mud (not counting "rail" type machines) - both with 39.5's. The first has a CJ2A with a 427 Ford & nitrous, & the second one has a Land Cruiser with a 477" Chevy & nitrous. Get this: the guy in the Land Cruiser has a 3.50 rear & a 3.07 front, TH350 & 205. He runs 2nd gear low range at 7,500 plus RPM's. Here's the really crazy part. He bought that motor used for $1,500 & has spent relatively little on it (just rings & bearings and I believe a little head work). What a steal!

I ran my 38X12.50 Swampers on the sand ONE time. It was real dry, loose stuff. The guys with the fatter tires did a lot better.

You don't want to air down 16.5" tires because of the way the bead seats on the rim. 15 & 16" rims have a much better bead - even on totally stock, non-beadlocked rims.</font color=purple>

TEX



[img]/wwwthreads_images/icons/wink.gif[/img] Got Mud?
G.U.M.B.O. Mud Racing

<font color=purple>There are a couple of different RPM formula's that are real handy.

First:
FD*MPH*336/TD = RPM

Second, turn that one around for:

MPH = (RPM*TD)/(336*FD)

In each case, FD = Final Drive, TD = Tire Diameter, RPM = RPM, & MPH = MPH.

I use both to try to plan "appropriate" gearing. Now, if you want to drive on the highway with 5.13's & 39.5's, it's gonna be humming.

5.13*60MPH*336/39.5 = 2,618 RPM's

4.56's would work better on the road:

4.56*60MPH*336/39.5 = 2,327 RPM's


BUT, 4.56's won't work as well in the deep mud. You won't have enough gear to pull 2nd. But, you should with 5.13's. So, figuring 5,000 RPM's, you'd get the following tire speeds:

(5,000*39.5)/(4.56*2*2.52*336) = 25.58 MPH

(2 is your T-case ratio & 2.52 is 1st gear)

For 5.13's, you can probably run 2nd (1.52)

(5,000*39.5)/(5.13*2*1.52*336) = 37.69 MPH


So, you can see how the 5.13's would be better in the thick stuff. But, since you have to drive it on the road, that's why I said it might be best to either go with 5.13's or the opposite extreme. With 4.56's, you're going to scream in 1st gear, but not have enough umpff to go to second. With a 454, you should be able to turn 1st gear with 39.5's & 4.10's or probably even 3.73's - even as heavy as your 'burb is.

So, with 4.10's in 1st:

(5,000*39.5)/(4.1*2*2.52*336) = 28.45 MPH

With 3.73's in 1st:
(5,000*39.5)/(3.73*2*2.52*336) = 31.27 MPH

So, even while the 4.56's would provide better acceleration, 3.73's & 4.10's would provide better overall tire speed based on the limits of your RPM's & gear selection.



Now, another option for you to consider is getting a 208 T-case. The 208 has a 2.61 low range. So, you could run 4.10's to let the motor loaf on the highway & still zing 2nd gear pretty hard in low range:

(5,000*39.5)/(4.1*2.61*1.52*336) = 36.14 MPH

This option works out real well for an awful lot of guys around here. The 208 isn't quite as durable as a 203 (which isn't quite as good as a 205), but it's not bad. </font color=purple>

TEX

[img]/wwwthreads_images/icons/wink.gif[/img] Got Mud?
G.U.M.B.O. Mud Racing

[The_Sandman_454]

Thanks for the advice, TEX! [img]/wwwthreads_images/icons/wink.gif[/img] [img]/wwwthreads_images/icons/cool.gif[/img] Got any general driving tips for the mud races, or mud in general? Anybody? [img]/wwwthreads_images/icons/wink.gif[/img]

Tim
"The_Sandman_454"
[img]/wwwthreads_images/icons/cool.gif[/img] '79 Suburban 4x4 454, 6" lift, 35x12.5s & '85 GMC S15 4x4

I have been the tech inspector for the UPMDA for the last few years. So if you have any questions fire away.

<font color=purple>General driving tips? Grip the wheel & mash the gas!!! It's generally (but not always) a good idea to follow the ruts everyone else runs. That way you don't have to cut your own path. </font color=purple>

TEX

[img]/wwwthreads_images/icons/wink.gif[/img] Got Mud?
G.U.M.B.O. Mud Racing

I use to run a 80 toy w/36" in the modified four banger class
when they still had mud boggs at Moroso Motor Sports Park,
even got in the money 5-6 times(not a lot of compition)
in the mud I ran boggers out back and sup swampers in the
front. the main thing is to stand on the go pedal (as close to
redline as you wallet can take) to keep the tires from loading up
don't wear good cloths and laces you shoes tight- one of my sneaks
is still out there somewere

HAWG WILD
<font color=red> ALL THOSE WHO WANDER ARE NOT NECESSARLY LOST </font color=red> [img]/wwwthreads_images/icons/cool.gif[/img]

Sandman, glad to see you are interested in competing. Where in Michigan are you? My brother and I are planning on going to the Lima Jamboree in May. We like the idea of a truck tug-a-war that they are going to have.

I am in Ohio, and there are 2 places that we go to for bogs. We always have a good time and they payout. They are not sanctioned, but pay the top 5 if memory serves me. The one place has two pits side by side and they let people play in it before competition begins,,, pretty nice, keeps the crowd involved and they pull you out. Some have made it through these pits.

The other one we go to, NOBODY has ever made it through. All kinds of stuff there,,, a Datsun 280Z on 39's.

We call both of them Hillbilly events, but a hell of good time.

See ya, RedDog

[The_Sandman_454]

I'm in a small town a little west of Saginaw... Tug-o-war, huh? Hmmmmm That sounds like it could be fun. [img]/wwwthreads_images/icons/wink.gif[/img] [img]/wwwthreads_images/icons/laugh.gif[/img] What kind of surface do they have it on? Slick mud, pavement, dirt?



Tim
"The_Sandman_454"
[img]/wwwthreads_images/icons/cool.gif[/img] '79 Suburban 4x4 454, 6" lift, 35x12.5s & '85 GMC S15 4x4