H1 crawl ratio

[LagunaH1]

When I was researching H1's prior to purchasing my 1997 HMCS, I was wondering about the crawl ratio. Here is what I thought to be true at the time:

"How does one calculate the total combined gear ratio in st gear, low range on an H1?
Looking at the specs, I'm not sure if, for example, the torque converter ratio of 2.2:1 should be included?
Here is what I think I know:
1st gear = 2.48:1
Torque converter: 2.2:1
Transfer case: 2.41:1
Axle: 2.71:1
Hubs: 1.91:1
So, 2.48x2.2x2.41x2.71x1.91 = 68.06:1 ?
Reference:
http://www.lynchhummer.com/changes/b....specs.700.jpghttp://www.lynchhummer.com/changes/brochures/97.specs.700.jpg"

I later learned that the torque converter should not the included in the equation, so:

2.48x2.41x2.71x1.91 = 30.9:1

Other model years may have different gears, and especially the Alpha's will have a different (better) crawl ratio.

 

[MaxPF]

You need to remember there is a distinction between crawl ratio and torque ratio when dealing with a torque converter driven automatic. With a manual, or an auto with the converter clutch locked (which only happens if your trans is capable of operating in 1st gear lockup AND you have installed a switch to do so), crawl ratio=torque ratio. With an automatic with an unlocked converter the crawl ratio is essentially infinite, since you can slow to zero wheel speed without stalling the engine. In this case it is the overall torque ratio you are concerned with since that determines "crawlability", and the torque converter multiplication should be included in that figure.

Also, most diesel converters have a stall ratio of 2:1 or less, but in general 2:1 is a good all-around figure to use.

 

[LagunaH1]

Thanks! The reason I started looking into this was I was trying to compare the H1 to my old H3 that had a really decent ratio of around 50:1. -That came in really really handy when crawling down very steep grades.

In the H1 I have never wished for lower gears going up anything, but I *have* once or twice wished for lower gears crawling down long steep slopes in the H1

 

[MaxPF]

That is the Achilles Heel of an auto with an unlocked converter; the advantages when climbing work in reverse when descending! The converter's turbine has to get wound up to stall speed before it will really drive the pump and start slowing you down. A converter lockup mod is a big plus in this scenario, but the 1st gear in an auto us still usually much taller than a manual with a granny low gear so you are still limited by that. Still, everything helps. A doubler or crawler box is a huge help as well since it will get the turbine spun up to stall speed at a much lower wheel speed. Some guys on Pirate have questioned the utility of a crawl box behind an auto, but I think this is exactly the scenario where they are a huge benefit.