4WD vs 2WD

Moderator: sandaltered

4WD vs 2WD

Postby Insta-Gator » Fri Apr 20, 2012 5:15 pm

I am finishing up a new ride that I hope to have to a track early this Summer. Although it is built for a specific class in the MRA (Renegade) and I plan to attend some mud drags with the car, I also built the car with sand drags in mind. Living in Northern Indiana, I am in the middle of several sand/dirt drag tracks and plan to check as many of them out as possible this summer. (I LOVE racing 300 ft!)

I will be running a taller tire on the rear of the car when mud racing than what my paddles are. And, the front tire will be the same height. So... my gear ratio will be off and consequently give me too much over spin with the paddles.

My question is, can I just plan to run the car in 2WD and not worry about front to rear gear ratios???

I have built a chain drive, and I can make up different sprockets to compensate, but is it necessary? Will the car be faster in 2WD? Will it be harder to make go straight?

Specs...
Tube Chassis Jeep (retains 2 stock frame rails)
108" wheelbase
4-link, coil over
Very low to the ground
632 Chevy, N/A, 1150 hp
Glide, brake
Engine pretty far forward per MRA rules (12" from #1 plug to center of axle tube)

Thanks for any advice! Brian
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Re: 4WD vs 2WD

Postby Bodacious » Sat Apr 21, 2012 6:19 am

Brian, you can run it in 2 wheel drive.
As long as your chassis is set up correct it will go straight in the sand, it's not like the mud were the front end is helping to keep you straight in some pits.
As far as going faster in 2 wheel drive I am not sure you will see much of a difference if you just drop your chain but leave all the extra weight from the front end and front drive shaft.
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Re: 4WD vs 2WD

Postby Insta-Gator » Sat Apr 21, 2012 2:24 pm

Thanks Steve. It may seem like a dumb question to sand guys, but I have raced for 20 years, and have never ran 2WD. On some mud tracks, it would be a challenge to stay in bounds without the front pulling. I know you've been there...

So if I want to actually gain some performance, I should pull out the front drivehshaft, chain and pillow block assembly. The only advantage is the weight, rotating and otherwise?
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Re: 4WD vs 2WD

Postby THE BOSS » Sat Apr 21, 2012 4:49 pm

i forgot to lock in the front hubs in Earls truck once, it lost ET but gained MPH
i belive it would vary from vehicle to vehicle and from whatever HP you running
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Re: 4WD vs 2WD

Postby sandaltered » Sun Apr 22, 2012 6:53 am

My Jeep ran better in 2WD. But was a little easier to handle in 4WD. Not much. It just liked to wheelie in 2WD even with just pulling the chain.
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Re: 4WD vs 2WD

Postby Bodacious » Sun Apr 22, 2012 8:31 am

The old rule of thumb was 1 pound of rotating weight was equal to 10 pounds of static weight, it's not that simple. The closer the weight is to the center of the rotation the less it matters.
So if you were to drop 5# on your drive shaft or 5# on your bead locks you would be much better off dropping the weight on the bead locks.
By just dropping the chain and unlocking the hubs you wil be reducing rotating weight allowing more power to be put to the rear tires, you will go faster.
The key would be that you have to be able to hook the car up in 2 wheel drive. Mikes Jeep hooked and went faster, as Tony said Earls trucks ET was slower but MPH was higher, my guess is the truck didn't carry the front wheels off the line, it didn't hook as well.
Another thing to keep in mind is less weight=lower ET. Can you make the whole front end a quick change? If you drop all the static weight and rotating weight from the front end and drive shaft will see a bigger change, Again, as long as you hook it up. The old rule of thumb for the 1/4 mile was 100 pounds was equal to 1/10th
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Re: 4WD vs 2WD

Postby Insta-Gator » Sun Apr 22, 2012 9:51 am

Thanks for the info. I think I will plan on running in 2WD. After I get some passes I will know how hard this thing is gonna hook and whether it would be worth having a
"quick change front". "Quick" is relative. I could make a 2WD front to swap out for racing sand, but I doubt that I could do it in a hurry! :lol:
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Re: 4WD vs 2WD

Postby shinn chassis » Wed Apr 25, 2012 6:42 pm

I remember years ago seeing some of the open class 4x4 guys with paddles unlock the hubs to run our water pumper class (2 wheel) and pick up 2 tenths. I have seen the 44 cut bogger class trucks tear up the frontend and still run some classes and slow down. I figured the cut tire guys just couldn't hook up and were over powering the rear tires.
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