Good Crawl Ratio for Manual Trans buggy ??

Yay!Gurrr

Yay!Gurrr

Better Faster Stronger
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Mar 17, 2005
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I'm penciling out what I'd like to shoot for as a crawl ratio for my buggy project. Normally this wouldn't be an issue with a vehicle, but with the transaxle setup what ever ratios I use ultimately affects my top speed.

Keeping in mind what I'm building...
~3000# 4cyl conventional OHV design (not DOHC) making ~120hp
Toyota axles w/ 36" radial tires.
Diffs will be run upside down.

I can hit the following crawl ratios and high speed in OD
1) 4.10s 58:1 and 43 mph @ 4500 rpm
2) 4.56s 65:1 and 38 mph @ 4500 rpm
3) 5.29s 75:1 and 33 mph @ 4500 rpm

Opinions ???
 
If it's a buggy... I'm guessing the lower the better.

Do you really ever get over 33 mph - even when spinning the tires?

Example - the gravel road at URE.. 25 mph is plenty...

Slightly off topic but if you're going to work the engine a little bit, keep an eye on the temp gauge the first few times out.
 
Before my build I was about 100:1 now I'm about 88:1. Not happy with it, I'll be setting up a crawl box soon.
 
Thanks for the PBB link, I looked sunday for like 2 hrs for it.. Don't think I tried 'crawl ratio' duhhhh... Everyone should read that before replying.. Mentioning your ratio with out considering your tire size and even engine size makes it hard to draw any parallels between setups.

Everyone else - I realize that 100:1 is great.. Some things to think about along with crawl ratio... How much of that ratio is to make up for a small or low hp engine in a rig with big tires. What is your power to weight ratio?

Let me pull up my spread sheet again. But I made some lines with info from peoples rigs I know what their specs are and one that I've ridden with and felt they were gear well enough (for their driving style) BRB...
 
So the spreadsheet #s
My 1 concern is running the 5.29s upside down.

This is what the funny part is... The i'm sure it doesn't measure up to the 100:1 folks, but I had felt my zuke buggy was gear well for its size/weight (1.98) and also that using sheldons TJ as an example from memory 4cy TJ 4:1s 4.88s 36s always performed well offroad... (2.05)

Of interest is that if I drop the RPM from 1000 to 600 the crawl speed goes way down... With my tuning shit I can easily get the RPMs down that low (my 307 chevy idles at 575) which is something else to think about... anyway...


crawl-speed.jpg
 
if you are that worried about the gears, you could always spend the money on a HP set and flip it in the rear, that way you would be on the drive side of the gears...

or you could run 4/10/4.30 in the diff, with a sami t-case getting feed from the transaxle, and get better crawl, yet keep your top speed... might make for better driveshaft lines too (think equal length, so only 1 spare)
 
.9375 ft/sec in 1st gear low. Use occasionally, slow but I like it and sometimes make obstacles others don't :)

1.77 ft/sec in 2nd gear low. What I use most of the time, I like it.

With a 4 cylinder motor and a 3400 pound rig I usually don't use any other gear combo for obstacles. I would however consider lower gear combos at times.
 
JC - the numbers help... ben- I wouldn't say I'm worried, I just want to consider all the options with cost in mind.. Flipping a HP chunk was gonna be my fall back plan..

It looks like I'm going to be using V6 chunks anyway so the 5.29s may be ok. We'll see ;)

Ok I think I'm good for what I need to do number wise... Anyone else feel free to add your crawl speed be curious to see what others' numbers are anyway.
 
My truck is probably 95 hp or so, 3000lbs, 36s

Crawl ratio is 83.76
crawl speed is 1.875 feet per second at 1000rpms

works fine for 90% of what i do, maybe once every 10 times out i might wish i had a little lower gear just to get positioned just right. It takes a little clutch work every now and then, but not bad to me at all.


I use that gear and 2nd double low a lot too. If im working to get up a ledge, or anything that takes a good bump, I get the front end up in first then shift into 2nd for the bump

49.66 crawl ratio
3.16 feet per second at 1000 rpms, up to 17.39 feet per second at 5500 rpms


I say the 5.29s are the best bet for most stuff. with a manual 75:1 isn't perfect, but its workable i guess.
 
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