ISUZUROVER
05-14-2004, 07:27 AM
From outerlimits4x4.com
http://www.outerlimits4x4.com/PHP_Modules/phpBB2/viewtopic.php?t=14820
Hi gents, Bill here. i will try to give you a brief rundown on what is involved in making up a crawler gearbox that fits to the pto aperture on Landrover series tranfercases and 4 speed LT95 tranfercases also.
The parts you will need are, an old Fairey overdrive to suit your particular transfer. This must have an input shaft and adaptor gear that is in good condition in the male and female spline area. You will also need to source the bolt on two speed high low range planetary gearbox from a Borg Warner Quadratrac transfercase as used on automatic Jeep wagoneers, Cherokees, CJ7's etc from circa 1980's If you plan on stealing one, these vehicles can be identified by having a rear diff that is offset to the right whereas non Quadratrac models have a centred rear diff. The only partts of the old overdrive you will use are, part of the gear case from the flange forward.
The adaptor gear, the input shaft and the cylindrical output gear. and some needle thrust and roller bearings.
the fairey input shaft is cut and resplined to engage with the female spline of the Quadratrac input gear. The Fairey cylindrical output gear is modified by grinding the teeth off the small helical gear at one end, and welding on the course splined dog from the old Quadratrac out put gear.
An aluminium adapter and blanking plate will need to be machined up to bolt the planetary unit to the Landy pto aperture. I have only performed this conversion twice. on a series 2a tranfercase and an Lt95 and I worked out the dimensions as I went along, so unfortunately i didn't make drawings. They have proven to be very strong with hard use over the years. I had to replace the roller bearing with a bronze bush on the adaptor gear due to brinelling as the planetary unit spends most of its life in high range. This brinelling also occurs on standard Fairey overdrives if overdrive is not engaged regularly. This conversion will not suit lt95's with the large handbrake assembly. you must adapt the smaller handbrake from a series i,2 or 3 or the early Rangerover 4spd. It could possibly also be adapted to the later Lt230 transfer case but as there are no dead overdrives around for these it would be more complicated and expensive.
The low range ratio in the planetary unit is 2.57:1 when this is combined with the LT95 gearbox and 3.54 diffs it yeilds an overall ratio in low low 1st gear of around 127:1 . Standard low 1st is around 48:1.
My own series 2a LandRover fitted with a D series Ford truck gearbox, suffix b tranfercase, crawlerbox, 3.54:1 diffs and 1:56:1 hub reduction in the portals yields an overall ratio in deep reduction 1st gear of 278:1.
Most people would think this ratio is unusable, but with lockers, good tyres, lots of ground clearance and gobs of axle articulation I have used this ratio to good effect on many occaisions.
Because the company that I was involved with "Off Road Rover" is no more. and I no longer possess the machining facilities that I once had, my assistance with this conversion unfortunately is limited to advice.
I have seen a similar pto mounted crawler box on a landcruiser transfercase in the showroom of Marks 4WD adaptors. It apears to be a coventional Mainshaft Layshaft (non planetary}design. They do not appear to like Rovers too much over there, so I am not sure how easy it would be to persuade them to adapt the crawler for rovers.
Incidently, I had heard that Ashcrofts crawler unit was withdrawn from the market because they were having too many warranty claims, not because of low sales volume. Ashcroft is not a volume oufit and one or two units per month would probably have been enough for them.
Regards Bill.
http://www.outerlimits4x4.com/PHP_Modules/phpBB2/viewtopic.php?t=14820
Hi gents, Bill here. i will try to give you a brief rundown on what is involved in making up a crawler gearbox that fits to the pto aperture on Landrover series tranfercases and 4 speed LT95 tranfercases also.
The parts you will need are, an old Fairey overdrive to suit your particular transfer. This must have an input shaft and adaptor gear that is in good condition in the male and female spline area. You will also need to source the bolt on two speed high low range planetary gearbox from a Borg Warner Quadratrac transfercase as used on automatic Jeep wagoneers, Cherokees, CJ7's etc from circa 1980's If you plan on stealing one, these vehicles can be identified by having a rear diff that is offset to the right whereas non Quadratrac models have a centred rear diff. The only partts of the old overdrive you will use are, part of the gear case from the flange forward.
The adaptor gear, the input shaft and the cylindrical output gear. and some needle thrust and roller bearings.
the fairey input shaft is cut and resplined to engage with the female spline of the Quadratrac input gear. The Fairey cylindrical output gear is modified by grinding the teeth off the small helical gear at one end, and welding on the course splined dog from the old Quadratrac out put gear.
An aluminium adapter and blanking plate will need to be machined up to bolt the planetary unit to the Landy pto aperture. I have only performed this conversion twice. on a series 2a tranfercase and an Lt95 and I worked out the dimensions as I went along, so unfortunately i didn't make drawings. They have proven to be very strong with hard use over the years. I had to replace the roller bearing with a bronze bush on the adaptor gear due to brinelling as the planetary unit spends most of its life in high range. This brinelling also occurs on standard Fairey overdrives if overdrive is not engaged regularly. This conversion will not suit lt95's with the large handbrake assembly. you must adapt the smaller handbrake from a series i,2 or 3 or the early Rangerover 4spd. It could possibly also be adapted to the later Lt230 transfer case but as there are no dead overdrives around for these it would be more complicated and expensive.
The low range ratio in the planetary unit is 2.57:1 when this is combined with the LT95 gearbox and 3.54 diffs it yeilds an overall ratio in low low 1st gear of around 127:1 . Standard low 1st is around 48:1.
My own series 2a LandRover fitted with a D series Ford truck gearbox, suffix b tranfercase, crawlerbox, 3.54:1 diffs and 1:56:1 hub reduction in the portals yields an overall ratio in deep reduction 1st gear of 278:1.
Most people would think this ratio is unusable, but with lockers, good tyres, lots of ground clearance and gobs of axle articulation I have used this ratio to good effect on many occaisions.
Because the company that I was involved with "Off Road Rover" is no more. and I no longer possess the machining facilities that I once had, my assistance with this conversion unfortunately is limited to advice.
I have seen a similar pto mounted crawler box on a landcruiser transfercase in the showroom of Marks 4WD adaptors. It apears to be a coventional Mainshaft Layshaft (non planetary}design. They do not appear to like Rovers too much over there, so I am not sure how easy it would be to persuade them to adapt the crawler for rovers.
Incidently, I had heard that Ashcrofts crawler unit was withdrawn from the market because they were having too many warranty claims, not because of low sales volume. Ashcroft is not a volume oufit and one or two units per month would probably have been enough for them.
Regards Bill.