Thread: Maxi drive reduction gears

Probably worth mentioning in this thread an unfinished project I have had for a while. With my uses for Defender 130 reckon it would be better with a slighly faster high range and significantly slower low. Can be achieved with LT230 from Discovery and Maxi drive low. Note though how an LT230 can be built with 1.27:1 High and 4.21 Low using only ONE PART as not supplied by Land Rover with advantage of standard non screaming helical gears in low and no grinding metal out of of case to fit them.
Starting with an LT230 that from serial number was originally in an early Rangie with Torque Flite auto. 1.003:1 high and 3.32 low. No good for Defender as high is too fast. Standard arrangement is 26 tooth input gear driving 41 tooth middle gear on cluster.
I did some looking, thinking and calculating and reckoned instead of using this, could get a 22 tooth input gear that instead drove the rear 44 tooth high range gear. ie Similar to the layout in a Series transfer box but back to front. Anyway, got a gear designed and cut for around $1,200. Without rear dogs for PTO or overdrive which would add to the cost for something I am unlikely to use.

Hopefully will get around to assemble and instal this soon. Would be interested to hear if anyone else anywhere has attempted it. Maybe a project for the likes of Ashcrofts to try.

I think the first LT230 transfer boxes had these 1.003 and 3.32 ratios. Seems to me Land Rover got the relative ratios between low and high right first time, including with 4th gear low and 1st high very similar. (ie subsequently they stuffed up!) For models requiring different ratios, it would have been better to have changed the input and central cluster gear sizes instead of changing the high range gears.

I'm intrigued Mox, but I haven't got an Lt230 of any type to play with to visualise whether it would work or calculate the high/low ratios.
However, a couple of mental calculations. The distance between centres of the input shaft to intermediate shaft is the same as for the output shaft and intermediate shaft. In that case the tooth count required on the input shaft to do what you say would be the same as the high range gear on the centre diff. Why not machine the teeth off the original input gear and have a centre diff high range gear electron beam welded to it instead of having a new gear cut?
bill.

Originally Posted by wagoo

...
PS. has anyone done a conversion whereby the high/low reduction box segment from a GQ/GU Patrol or Toy Hilux t/case has been fitted to the front of an LT230?

Yes. Someone from up Coffs Harbour (NSW) way was doing this using part of a GQ/GU transfer case. I haven't spoken to him about this for a well over 12 months, but back then he was close to having the doubler finished.

IMHO, this has some advantages ( less power loss for one) over the planetary gear set in the crawler unit.

Originally Posted by wagoo

I'm intrigued Mox, but I haven't got an Lt230 of any type to play with to visualise whether it would work or calculate the high/low ratios.
However, a couple of mental calculations. The distance between centres of the input shaft to intermediate shaft is the same as for the output shaft and intermediate shaft. In that case the tooth count required on the input shaft to do what you say would be the same as the high range gear on the centre diff. Why not machine the teeth off the original input gear and have a centre diff high range gear electron beam welded to it instead of having a new gear cut?
bill.

The distances between the shafts may possibly appear the same when trying to measure the spacings on a box installed in a vehicle but they are not. It is about 110 mm between input and intermediate shaft and 120 mm between intermediate and output shaft. Not sure if these are exact, which bloke who cut gear would have had to measure to design it. Anyway, it was within a small range`for which a 22 tooth gear could be made to fit and drive the 44 tooth high range one from the top side.

A point to note re replacing transfer box onto gearbox in vehicle: Seems it is normally easiest to take the input gear out with most boxes. (of course after it has been in place to get tapered roller bearing preload spacer shims in place) However, the standard input gear on an LT230 with 1.003 high cannot be removed or replaced straight out of the rear because high range gear on the intermediate cluster is larger than the middle one it drives. My modified input which drives high range gear does not have this problem.

Originally Posted by mox

The distances between the shafts may possibly appear the same when trying to measure the spacings on a box installed in a vehicle but they are not. It is about 110 mm between input and intermediate shaft and 120 mm between intermediate and output shaft. Not sure if these are exact, which bloke who cut gear would have had to measure to design it. Anyway, it was within a small range`for which a 22 tooth gear could be made to fit and drive the 44 tooth high range one from the top side.

A point to note re replacing transfer box onto gearbox in vehicle: Seems it is normally easiest to take the input gear out with most boxes. (of course after it has been in place to get tapered roller bearing preload spacer shims in place) However, the standard input gear on an LT230 with 1.003 high cannot be removed or replaced straight out of the rear because high range gear on the intermediate cluster is larger than the middle one it drives. My modified input which drives high range gear does not have this problem.

Thanks for the explaination Mox. Just as purely a mental exercise I'm now thinking again about Sergs suggestion for a 3 spd transfer case. With your modified arrangement, the centre gear of the intermediate cluster becomes redundent. If the intermediat gear were made into a 3 piece unit similar to an LT95,and that redundant helical gear were to be replaced with a spur gear come dog clutch, then a mating spur gear could possibly be mounted on splines machined on the hub in front of your new 22 tooth helical gear.This spur gear set would need to be of a lower ratio than your 22/44 tooth gear set, otherwise it would be quite silly and impractical, because high and low range would be relatively quiet helical gears whilst the additional intermediate range would be noisey spur gears.
Bill.

Originally Posted by Bush65

IMHO, this has some advantages ( less power loss for one) over the planetary gear set in the crawler unit.

Your comment above had me scratching my head for a minute John, until I took a closer look at the photos of Petes crawler and noticed that the ring gear is locked permanently to the gear case, so that even in high, where the sun gear is locked to the planetary gear carrier, the planetary gears are still circulating around both the sun gear and the ring gear. On my Quadratrac based unit in high, the sun, planetary and ring gear are all locked together and merely revolve as an additional flywheel, so very little in the way of frictional losses or heat generation.
Bill.

Originally Posted by wagoo

Thanks for the explaination Mox. Just as purely a mental exercise I'm now thinking again about Sergs suggestion for a 3 spd transfer case. With your modified arrangement, the centre gear of the intermediate cluster becomes redundent. If the intermediat gear were made into a 3 piece unit similar to an LT95,and that redundant helical gear were to be replaced with a spur gear come dog clutch, then a mating spur gear could possibly be mounted on splines machined on the hub in front of your new 22 tooth helical gear.This spur gear set would need to be of a lower ratio than your 22/44 tooth gear set, otherwise it would be quite silly and impractical, because high and low range would be relatively quiet helical gears whilst the additional intermediate range would be noisey spur gears.
Bill.

how much $$ shipped to 4214?

Originally Posted by Bush65

Yes. Someone from up Coffs Harbour (NSW) way was doing this using part of a GQ/GU transfer case. I haven't spoken to him about this for a well over 12 months, but back then he was close to having the doubler finished.

IMHO, this has some advantages ( less power loss for one) over the planetary gear set in the crawler unit.

so does the give 4 ranges?