Scooby Jim Posted February 8, 2013 Author Share Posted February 8, 2013 It looks like just the crown wheel is KAM. The Sun gears are 10 spline and KAM never made HD 10 spline shafts, only a 24 spline series conversion. That and its still a 2 pin carrier. Steve Cheers bud Quote Link to comment Share on other sites More sharing options...
bill van snorkle Posted February 8, 2013 Share Posted February 8, 2013 The diff in my 109 hadn't been messed with other than a new pinion seal, and I don't think our Lightweight diffs had been fiddled with either. It's a good point about the diff carrier perhaps being a 3.54 unit to accommodate the KAM gear and shim. If that is the case, and it has a filler plug on the carrier, than that will solve Jim's problem with oil levels on his 3.54 swap (other thread) - he could swap the 3.54 internals from one of the new diffs to this carrier, giving him the new diff ratio he wants and a filler plug. Actually I think we have different terminologies for describing diff components.What I refer to as a carrier is the component that the crownwheel bolts to. The 3.54:1 carrier has a greater offset at the crownwheel flange to allow for the larger diameter 3.54 pinion gear when compared to the small 4.7 gear. I think what you refer to as the carrier (with filler plug) is what is usually called the pinion housing. Quote Link to comment Share on other sites More sharing options...
bill van snorkle Posted February 8, 2013 Share Posted February 8, 2013 No, the earlier KAM gears were designed to fit in to series casings and on series carriers and had to use a 3.9mm spacer when fitted to metric 3.54 carriers. The tooth cough should be 10 on the pinion and 47 on the Ring gear which gives you 4.75:1 ratio - close enough to get away with when combined with a 4.7:1 ratio in the opposing axle without causing wind-up. Are you sure you have that correct? From memory, and it has been 10 years since I have had a 4.75:1 ring and pinion in my hands, but I recall they had a tooth count of 8 and 38. That what was supposed to make them stronger. Less but thicker teeth. Quote Link to comment Share on other sites More sharing options...
Off Road Toad Posted February 9, 2013 Share Posted February 9, 2013 You are of course absolutely correct, sometimes the brain doesn't match what the rest is doing. Thank you for pointing this out as it would have caused confusion. Steve Quote Link to comment Share on other sites More sharing options...
bill van snorkle Posted February 9, 2013 Share Posted February 9, 2013 You are of course absolutely correct, sometimes the brain doesn't match what the rest is doing. Thank you for pointing this out as it would have caused confusion. Steve You are welcome Steve. I do have a question you or someone else may have the answer to. Have destruction tests been carried out on KAM and Ashcroft 4.75 ring and pinions to quantify in percentage terms, just how much stronger they are than the standard 4.7 jobbys? Bill. Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 9, 2013 Share Posted February 9, 2013 Am I right in saying the weakness in standard 4.71 diffs is their flexing, allowing the crown and pinion to move apart, reducing the contact area of the teeth which causes them to strip (cured by pegging)? As I understand it, the 3.54 is stronger just because the crown wheel and carrier thickness prevent that flex, keeping the teeth messed, in which case the KAM gears should be similarly strong. Quote Link to comment Share on other sites More sharing options...
Off Road Toad Posted February 9, 2013 Share Posted February 9, 2013 I haven't worked for KAM for two years now, but while I was there everything was destruction tested independently and on properly calibrated rigs. This also included sample material analyses as well. I believe (from memory) the LR gears were made from a very very good spec metal but the aftermarket ratios gained their strength improvements from the tooth counts (allowing bigger teeth) and also the later KAM gears had material added to the back of the crown wheel which sort of wrapped around the carrier end flange and thus helped with crown wheel flex. As Snagger suggests the main failure point is usually losing teeth when the crown wheel flexes away from the pinion. Series 4.7's also have weak and very thin teeth compared to the other ratios which is partly why they don't survive very long if used in a higher powered Defender for example. Pegging works very well to prevent CW flex BUT the biggest issue is the bearing towers and caps flexing on the main housing, we now (megasquirt v8) now build up our diffs pegged and with longer 12.9 carrier bolts as the standard 8.8's bend and twist horribly when you overload them. I have just built up today an Ashcroft locker with peg and an absolutely massive 4.375 ratio CWP set, the teeth are HUGE! Hopefully Nige could put up the pic of it that he took today. Steve Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted February 9, 2013 Share Posted February 9, 2013 How come the 7th pic in the OP is a different diff to the busted one, it does not have lock tabs on the crownwheel bolts, which are also UNF bolts, and you can see the planetary cross shaft is still in place when looking thro the halfshaft hole. Quote Link to comment Share on other sites More sharing options...
bill van snorkle Posted February 9, 2013 Share Posted February 9, 2013 In a previous life I worked as a light and heavy vehicle differential and manual transmission specialist for many years.I pegged my own 6x6 LandRover diffs on self made 4 pinion carriers around 30 year ago.All this helped a bit, but I still broke quite a few crownwheels and pinions .There is only so much one can do to compensate for a poor design. As weak as the tooth section is, I do not believe for a second that LandRover crownwheels flex. It is the standard carriers that flex, and that is why the more rigid aftermarket 4 pinion carriers improve the situation. Even so, crownwheel to pinion tooth separation can still occurr due to , for want of a better term, flex at the carrier bearings.That is where pegging comes in. Anyone who has a pegged diff on the bench can test this by adjusting the carrier bearing preload to spec, then screw the peg bolt up hard against the crownwheel whilst having a dial indicator needle on the back face and watch how far the crownwheel can be moved.Without pegging. you could screw the bearing adjusters up tight to prevent that movement, but the bearings would likely burn out fairly quickly. Bill. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted February 9, 2013 Share Posted February 9, 2013 Hopefully Nige could put up the pic of it that he took today. Steve Oh go on then Std vs HS teeth set : Dramatically shows the differences of tooth count ! Massive HD CW&P and pegged to boot ! Nige Quote Link to comment Share on other sites More sharing options...
bill van snorkle Posted February 10, 2013 Share Posted February 10, 2013 Oh go on thenStd vs HS teeth set : 44 pinion.JPG std vs HD.JPG built 44.JPG Dramatically shows the differences of tooth count ! Massive HD CW&P and pegged to boot ! Nige Well they certainly look stronger, and obviously are stronger, otherwise they wouldn't bother making them.But I still wonder by how much. I assume the root diameter of the pinion teeth is closer to the centre of the shaft,so there would be a bit more torque trying to shear them off. If those who have got them are happy with them I might buy a pair or 3 of opposite cut 4.75's for my 6x6 should I decide to resurrect it. Bill Quote Link to comment Share on other sites More sharing options...
Off Road Toad Posted February 10, 2013 Share Posted February 10, 2013 I know Nige is running 4.75's in his stupid 325bhp 5.2 90 with 35" Simex and lockers with no problems! YET! Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted February 10, 2013 Share Posted February 10, 2013 I know Nige is running 4.75's in his stupid 325bhp 5.2 90 with 35" Simex and lockers with no problems! YET! Where did those other 17 BHPs dissappear to Toad, you knoicked them for that Tedious 5 of yours ? Nige Quote Link to comment Share on other sites More sharing options...
Scooby Jim Posted February 10, 2013 Author Share Posted February 10, 2013 How come the 7th pic in the OP is a different diff to the busted one, it does not have lock tabs on the crownwheel bolts, which are also UNF bolts, and you can see the planetary cross shaft is still in place when looking thro the halfshaft hole. Sorry my mistake that is the 3.54 Disco diff that going to replace the broken one. Oh go on thenStd vs HS teeth set : 44 pinion.JPG std vs HD.JPG built 44.JPG Dramatically shows the differences of tooth count ! Massive HD CW&P and pegged to boot ! Nige That looks awesome!! Fair play have learnt a bit reading these comments, cheers guys. Quote Link to comment Share on other sites More sharing options...
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