1:1 Series Landrover Transfer Case
I've been meaning to do this for years, but just never got around to it. Each time I go any distance in Lucky Lucy (109 GS Landrover) I think she's undergeared and I should get on and do something about it. There's several options,
I find it's easier to think in overall ratios as I can relate them to the final drive in other vehicles I've owned.
Standard 5.396:1
Overdrive 4.220:1
Ashcroft 4.089:1
Rangerover diffs 4.064:1
My mod 4.7:1
Standard is obviously too low, overdive is too expensive and fragile, Ashcroft is expensive at £327 by the time the carriage and vat is added and I think it's a little high geared for my use, RangeRover diffs screw up the low ratio and I need low ratio regularly. My mod is to take a standard 31tooth output gear, and use it as an input gear, giving a 1:1 transfer ratio instead of 1.148:1. This does alter the series III low ratio from 2.375:1 to 2.05:1 which isn't good, but if you use the IIA 2.888:1 intermediate and low output gears you get a low ratio of 2.53:1 which has to be good. The 2.888 int. gear was produced both with the small shaft and the later larger shaft. Large shaft Int. gear part 521330, low gear matching part 235438.
This a table borrowed from the Mustang Sallys Landrover Pages site. I've modified it with the 1:1 gear ratios and the two possible low ratios. I have emailed a few times and asked permission to use this table, but have received no response..... any complaints and I'll take it down.
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Standard transfer input gear and 9" grinder butchered version.... :o)
The gears are case hardened, but once you grind through the 20thou hard layer, they machine very nicely.
"spline" section for the new gear finished on the lathe. The shaft is a cut down mainshaft which was part of my never finished mid engined, four wheel drive, Rover V8 powered Hillman Imp!!! Foolishness, but I was only about 18 at the time........ :o)
Output gear about to be attacked with the grinder.
PTO spline cut off and the centre hollow ground to get rid of the case hardening.
Boring the centre out. I didn't grind out the centre because I needed it to true the gear up in the lathe. The boring bar tip wasn't very pleased at being asked to cut through the case hardening, but I took a deep cut to get though it in one cut rather than trying to "wear" my way through it and the tip survived, just.....
The two bits of gear machined and V ground for welding.
Pressed together.
Close up of the V for the weld. I think this is deep enough, but only time will tell if it's strong enough......
Welded, not my best welding ever, but should be fine.
To work out the new position for the intermediate gear shaft, I needed some "plugs" to fit in the transfer case holes. The quickest way is to cast them in aluminium with lost foam patterns and dry sand. Quick, cheap and fun :o)
Wendys horse buckets, don't tell her....
Metal ready for the pour.
Poured and a couple of ingots from the extra metal. Better to melt too much, than not enough.
Plugs in the case.
The position of the shafts means that the cross isn't very clear and it's really vague exactly where the hole should be, time for plan B.
Plan B, which is what I should have done to begin with.
Gears fitted to the dummy shafts with 9thou feeler gauges between the teeth to get the correct position and backlash.
Before welding. Note the groove at the top of the hole for the oil to run down and the groove round the edge of the hole for the oil to flow round so it can get inside the Int. gear to lubricate the bearings. The thrust washers have three cut outs to let the oil get past them.
Mig welded.
Other side of the case welded, note the mistake. I should have built up the relieved part below the shaft.
Setting up the case in the mill with the gears on the dummy shafts and the 9thou feelers in place.
Final cut with the boring bar.
It fits !!! Spot on, nice close fit with no play at all.
Fitted the gears and thankfully the tooth clearance is about right, 8thou and 9thou, that'll do me.
This is the second mistake I made, trying to bore the second side with too long a tool.
The hole appeared to bore OK, but closer inspection reveales that the cutter was flexing and due to the interupted cut the hole was far from round. Also should have welded up the lower edge of the hole before I started.
Time for a rethink. I made a dummy shaft and centred it on the mill.
Weld the hole back up, put the case on dummy shaft, clamp it to the bed and the second hole is easy. This is what I should have done the first time, must be getting thick in my old age..... :o) Note the chunk of weld added below the hole.
With both holes bored it's time to sort out the
thrust faces.
The standard thrust face has a recess for the
thrust bearing. It seems to me that this is just to make assembly
easier and I can do without it, so I'm just making them flat,
with the oil channels of course.
The thrusts have a tang to stop
them rotating and I'll bend this slightly so it locates in a wee
groove.
Face No.1 almost done and thrust held in place to see how it looks. More later, it's time for chicken tika masala......
Had a bit of a disaster with the mill feeds. The feeds are powered by DC motors with an elderly speed control board which decided to rebel and fry some components, reed relays and resistors. After much soldering I refitted the repaired board only to have another part cook itself, my fault this time as I think the direction switch shorted out because I'd left it half dismantled while trying to find the first fault. Anyway, ordered the new bits, more reed relays, resistors and some veroboard to make a wee add on bit to make modern parts fit a 70's PCB. Still waiting for one of the reed relays to turn up and the ETA is 16 days away despite the RS website claiming to have the bits in stock. Couldn't wait that long, so just fed it by hand.
To get clearance for the mill I had to take a bit off the inside of the case below where the thrust goes. I don't like doing this kind of thing as it feels like bodgery, but without buying a larger diameter cutter there was no alternative. This side of the case has the undercut section which I welded part of up. The blue line marks the thickness of the thinnest part of it, but most of it it thicker than that. It'll be fine.... :o)
Time to bore the relief for the wide part of the shaft, in the small hole side. I'm also making the relief a little deeper than normal to let me put an "O"ring in there to try and keep the oil in with the hole in it's new exposed position.
Well, that seemed to work :o)
Turned the cutter round in the tool and cut the oil groove in the other side of the case.
Shaft in place with the nicely compressed "O" ring just about visable.
Oil channel cut with the die grinder.
I filed wee grooves for the thrust washer tangs to locate in. The standard setup has the tang in the oil groove, but I had to machine this bit away while doing the thrust faces.
Checking the intermediate gear end float, needed to make a 15 thou shim to get it within tolerance.
Assembled transfer box, ready to go in.
I'm a little disappointed with the clearances, the input to intermediate gear has almost no clearance, while the int. to output is just about right. I'm hoping it'll be OK, because I really can't be bothered doing it all again. It'll either be fine or it'll eat itself...... :o)
I slept on the clearance problem and this evening I tried fitting the intermediate gear (wrong low ratio) which I'd used to work out the shaft position. Clearances are fine with this gear. I can only assume that the new int. gear is slightly oversize and the shaft is slightly off centre. I'm not convinced the new int. gear is a genuine part. Put it all back together (again!!) and took it for a test drive. It's hard to judge whether the high ratio alteration has been worth it without driving to the main road and that's half an hour away, so that'll have to wait. Low ratio is noticably lower on the climb back up the track to the house. The box has a slight whine, but it's really pretty quiet although I haven't gone over 50 mph yet. If I'm lucky the gears will bed in fairly quickly, quieten down and gain a little clearance at the same time...... time will tell :o)
Done about 50 miles now and it's as quiet as a mouse :o) Main road driving is definately more relaxed, but the edge is off the acceleration and hills that were easy in 4th gear are now 3rd and a half. Probably time I had the annual? look at the ignition system.......
Tweaked the timing, new plugs and modified the air filter, much better :o)
Done lots of miles now and it's fine. It has lost a fair bit of acceleration in fourth, but it's much more civilised to drive and I think it's been worthwhile to do. Bear in mind that I run on LPG and the power is down a bit, petrol would probably pull fine in fourth. I find reverse a litle high and often slip into low for reversing trailers now. I think the Ashcroft conversion would have been a disaster for me if I'd gone that route. Even higher fourth and higher reverse, it would have been bloody useless......
This is poor neglected "Lucky Lucy" about to have her innards tweaked, I may even paint her some day... :o)