By Bill Bettridge (Billb) on Wednesday, August 29, 2001 - 09:50 am: Edit

Need some schooling on this from those in the know - or preferably those who have gone this route:

Besides cost (ouch) are there any downsides or problems associated with the low range gear sets as sold by GBR (or anyone else for that matter)?

Off road - benefits seem obvious, but what are the on-road side affects?

Not ready to drop $2K yet, but am very curious about those who have made this mod.

Thanks

By RVR OVR (Tom) on Wednesday, August 29, 2001 - 10:50 am: Edit

You may have more luck on the d90 forum on Yahoo groups. I have seen this discussed in length there...

By Ron on Wednesday, August 29, 2001 - 10:51 am: Edit

And no one had bought it yet :-)

Ron

By Joe Casey on Wednesday, August 29, 2001 - 11:14 am: Edit

i like the ashcroft underdrive better. it gets you lower for a little more. i think the ashcroft is 2700. but it gives you a low gear equiv. to 8.9 not 4.3. also it leaves the low range stock unlike the GBR which if you drive in snow, you might need a little more mph rather than crawl numbers. just a thought.

JC

By gil on Wednesday, August 29, 2001 - 01:58 pm: Edit

what is the "Klune-V?" is that not also a t-box "underdrive"? anyone know anything about it?

By Ron on Thursday, August 30, 2001 - 03:22 am: Edit

It mounts between the tranny and the T-case, have no idea if you could make it work in a rover drivetrain.

Ron

By Ho Chung (Ho) on Thursday, August 30, 2001 - 08:31 am: Edit

bill,

rich hills ( D90 owner in the d90 list) has the LT230RC. he seem to have all the cool toys i want...

you can also read some more about it at
http://www.greatbasinrovers.com/trnscsgear.html#maxi


a note on the ascroft crawler box, it's way too big to be nicely fitted in the disco. i was considering that route, but didn't seem to be an easy operation.

By Bill Bettridge (Billb) on Friday, August 31, 2001 - 02:52 am: Edit

Thanks all - I read all the GBR info, but was hoping a Disco guy had made the plunge! I definitely don't want to add any type of sep. crawler box - just more crap to be in the way and another piece to break - which is why the gear set seems a good idea (although outrageously expensive)

Bill

By Ron on Friday, August 31, 2001 - 03:40 am: Edit

Bill,

If you want to ask Rich about it I have his email. I would think if you are spending 2k mine as well just convert to an atlas and get a 14 bolt rear, cost would be comparable to the LT230 RC and a built rover rear.

Cheers
Ron

By John on Friday, August 31, 2001 - 06:34 am: Edit

Can anyone enlighten me on this? The GBR paragragraph says spur gears vrs. helical gears are used in the RC boxes for strenght.A spur tooth gear has 100 % contact/load on 1 tooth while turning. A helical gear has 1 point of contact/load on many teeth as it turns. Oval racers use spur tooth gears for shifting ease..helicopters use helical gears for strenght/noise reduction. Is the spur gear stronger than a helical? Just looking for thoughts on this...

By Kyle Van Tassel (Kyle) on Friday, August 31, 2001 - 06:40 am: Edit

John from what I hear of this thing I am not fond of its strength on the long haul. Its basically some new gears but other existing parts are modified along the way. One of the shafts is cut in two as well... Definately a nice toy but as someone mentioned before it limits your abilities. Instead of hitting some mud in 2nd gear you will have to start thinking about selecting OD to get the desired wheel speed. I like that other bastard that gives you a second low range.. Dont like the added complications but for a toy it seems the most logical..

Kyle

By RVR OVR (Tom) on Friday, August 31, 2001 - 06:43 am: Edit

"that other bastard" LOL. Kyle, I love your way with words.

Isn't the Low range in a disco low enough? Don't we have something like 3.27:1. I thought a lot of jeep guys strive to have 4:1. Seems like that we are there as long as we have 4.10's and don't go over 33" tires...

Tom

By Jeff Price on Thursday, September 06, 2001 - 09:30 am: Edit

The allowable load on a gear tooth is calculated by the:

Lewis equation
F = sbY/D.P.

Where
F = ALLOWABLE TOOTH LOAD
s = MAT'L ENDURANCE LIMIT
b = FACE WIDTH
Y = LEWIS FORM FACTOR
D.P. = DIAMETRAL PITCH

The spur gear has (I believe) a larger contact width for a given gear width than the hypoid gear.
I will double check some old textbooks tonight for the hypoid numbers.

-jeff

By John on Thursday, September 06, 2001 - 10:05 am: Edit

"The spur gear has (I believe) a larger contact width for a given gear width than the hypoid gear."
If you have a 1" wide spur tooth and a 1" wide helical tooth, the helical tooth has more operating width determined by the angle of the helical tooth. A spur tooth just contacts on the pitch line of 1 tooth, the helical gear slides along the helix angle of several teeth, depending on dias.and helix angle. But I dont know if I am right or wrong but I am sure curious.

By Jeff Price on Monday, September 10, 2001 - 04:41 pm: Edit

I pulled out Shigley and Mischke, Standard Handbook of Machine Design, and
they just state "As a result of the increased total area of tooth contact, the load capacity of helical gears is generally higher than that for
equivalent spur gears". There is a parameter for helical gears called the face contact ratio describes the amount of additional face contact due to overlapping of the angled teeth. At a helix angle of 35% this is 2. Which means you have twice as much tooth surface engaged as a straight spur gear. Helical gears also run quieter because they have a more gradual tooth
engagement. The only limitation in the employment of helical gears is the
they generate an axial loading proportional to the force at the tooth (torque over moment arm) and the tanget of the helix angle psi. Perhaps the case isn't strong enough to bear
that loading. Spur gears for strength seems to be incorrect. I suppose there could be some peculiar combination of diameter and diametral pitch and case design, or lack of room that makes the spur gear stronger.

Three interesting things,

One: I am looking at the exploded view of the transfer case on alldata and
all the gears are depicted as helical gears. What am I missing here?

Two: I had the disco in at the dealer for a drive train clunking noise (especially on the overrun)and the service adviser droid gave me the standard "well it has spur gears" line of crap, I persevered and the mechanic found the input shaft was excessively worn. They replaced the shaft and clunk gone. I really think they must hire people off the street. I had the same problem with my '87 Range Rover or else they would have gotten away with it (the vehicle was still under warranty then).

Three: You might not find so interesting. When you look at the mathematics for helical gears for a while you realize that you can use the helical
equations for spur gears, with a helix angle OF 0. This makes it easier to make direct comparisons.

PS- I incorrectly put hypoid when I meant helical in the earlier post.
Sorry

-jeff