Daan Posted January 21, 2007 Share Posted January 21, 2007 I am giving my landy a bit of a once over after having served myself pretty good for around 5 years. Part of this is by pulling the diffs to have a look. I was worried to see the rear crownwheel bolts were only fingertight. This is on a detroit diff with 4.7 KAM crwonwheel and pinion and a 4.7 spacer. I run 35 inch simex. The whole thing has obviously been worked pretty hard over the last 5 years. I fitted the whole setup myself, using loctite and 40-45 LB-ft of torque as per manual. I seem to remember that the required torque seemed quite low. My question is whether I can up this a bit, say 50% to prevent this happening again. Anyone done this? It is fitted with BSP bolts and thick washers. Another trick I was thinking is to use Schnor washers, to stop them getting undone. I have heard of more people having had this problem and the question is obviously whether people have solved the problem succesfully. Cheers, Daan Quote Link to comment Share on other sites More sharing options...
SiWhite Posted January 21, 2007 Share Posted January 21, 2007 Daan, I've had the same problem on my ARB centre with a Rover 3.54 crownwheel. They were Loctited in place but, as per the ARB instructions, I didn't clean the threads first to remove the factory oil. Hence, Loctite didn't work and the bolts came out! I'm just finishing fixing my Lathe before I can repair the centre, and then I'll be thinking about how to secure the bolts in place. Current thinking (seeing as I don't trust Loctite any more!) is either to drill the bolts and use locking wire, or to put a tack of weld on the bolts. I'll be interested to hear how you get on.... Quote Link to comment Share on other sites More sharing options...
will_warne Posted January 21, 2007 Share Posted January 21, 2007 Daan, these are all of the guys I know who have KAM 4.75s (seem to be badly affected due to the width of the crownwheel). Ali Read had this happen - diff was rebuilt and no issues when vehicle was sold about 18 months afterwards. Jules Read hasn't had a failier although, AFAIK, he hasn't pulled his diffs since he killed his truck Graham Antill had this happen at an event - not sure if he ever solved the problem. Mark McFarlane (aka Tonks) - no problem AFAIK Trev (aka LR90) - no problem AFAIK IIRC KAM started selling stronger bolts to try and solve the problem. Quote Link to comment Share on other sites More sharing options...
orange rover Posted January 21, 2007 Share Posted January 21, 2007 i just took my front diff out, bolts were really loose. true track with ashcroft r&p. didn't install it myself, so don't know whether loctite was used, didn't see any traces though so i would think not. re-tightened the bolts to the correct torque, using stronger (red) loctite. did them one by one + used lots of brake cleaner on bolts and threads to make sure everything was clean. tried undoing the bolts a day later, really thight. put the diff back in no keeping my fingers crossed. cheers orange Quote Link to comment Share on other sites More sharing options...
Adrian Turner Posted January 21, 2007 Share Posted January 21, 2007 I've had it on both ARB'd 3.54 diff's Quote Link to comment Share on other sites More sharing options...
will_warne Posted January 21, 2007 Share Posted January 21, 2007 I've had it on both ARB'd 3.54 diff's Mine were fine when they were pulled last March after 3 years. Ade, did you use new bolts? Quote Link to comment Share on other sites More sharing options...
GBMUD Posted January 21, 2007 Share Posted January 21, 2007 Mine were fine when they were pulled last March after 3 years. Ade, did you use new bolts? Only one year of actual use though, Chris Quote Link to comment Share on other sites More sharing options...
maverick Posted January 21, 2007 Share Posted January 21, 2007 you could always drill the bolts and lock wire them so it cant happen Quote Link to comment Share on other sites More sharing options...
Daan Posted January 21, 2007 Author Share Posted January 21, 2007 you could always drill the bolts and lock wire them so it cant happen I dont think lockwire stop them getting loose, but they do stop them getting undone, once they are loose if you see what I mean. I have a more direct question to Mr ashcroft (who is on this forum): what torque are you using for the crownwheel bolts with this kind of setup? Thanks, Daan Quote Link to comment Share on other sites More sharing options...
ashtrans Posted January 21, 2007 Share Posted January 21, 2007 I dont think lockwire stop them getting loose, but they do stop them getting undone, once they are loose if you see what I mean.I have a more direct question to Mr ashcroft (who is on this forum): what torque are you using for the crownwheel bolts with this kind of setup? Thanks, Daan funnily enough we have been looking into this last week after also having had this problem, we go to 45 ft/lb a med strength loctite on brake cleaneered threads but this is still not good enough for some applications, KAM use a 3/8 BSF thread like the older 4.7 series diffs, this is quite a corse pitch not as good as the later 3/8 UNF, all 3.54's and our 4.11's use the 3/8 UNF , you can buy higher tensile 12.9, 3/8 UNF bolts but they are all socket caps and thus do not have a shank which is very important to locate the crown wheel, the later P38 diffs use the same thread in 12.9's, hex head with integral washer but have no shank, not ideal. (and they are £ 2 each), we are doing 3 things : 1) costing up a batch of 2000, 3/8 UNF, 12.9 tensile, 1 1/8", hex head with 3/8" shank and integral washer, 2) being higher tensile we can fit to a higher torque, waiting to speak to a guy tomorrow who has these figures, 3) buying high strength permanent fixing loctite. should do it, Dave Quote Link to comment Share on other sites More sharing options...
Adrian Turner Posted January 21, 2007 Share Posted January 21, 2007 Mine were fine when they were pulled last March after 3 years. Ade, did you use new bolts? No! old bolt's but with thread lock after cleaning with brake cleaner! if (when) i brake a shaft i'll be having a close lok at the bolt's! Only one year of actual use though, Chris yeah! but not a whole year!!! Quote Link to comment Share on other sites More sharing options...
Adrian Turner Posted January 21, 2007 Share Posted January 21, 2007 Forgot to add, i'm thinking of changing my 3.54's to 4.11's to give me more option's with gear selection from the box! i like to use 2nd and 3rd and the tdi's not to hot at pulling away on a long climb in 3rd! So when i change the C/p's i'll have a close look at the bolts first! Quote Link to comment Share on other sites More sharing options...
Daan Posted January 21, 2007 Author Share Posted January 21, 2007 funnily enough we have been looking into this last week after also having had this problem,we go to 45 ft/lb a med strength loctite on brake cleaneered threads but this is still not good enough for some applications, KAM use a 3/8 BSF thread like the older 4.7 series diffs, this is quite a corse pitch not as good as the later 3/8 UNF, all 3.54's and our 4.11's use the 3/8 UNF , you can buy higher tensile 12.9, 3/8 UNF bolts but they are all socket caps and thus do not have a shank which is very important to locate the crown wheel, the later P38 diffs use the same thread in 12.9's, hex head with integral washer but have no shank, not ideal. (and they are £ 2 each), we are doing 3 things : 1) costing up a batch of 2000, 3/8 UNF, 12.9 tensile, 1 1/8", hex head with 3/8" shank and integral washer, 2) being higher tensile we can fit to a higher torque, waiting to speak to a guy tomorrow who has these figures, 3) buying high strength permanent fixing loctite. should do it, Dave Hi Dave, thanks for this quick reply on a sundaynight, its weekend mate! I had fitted capheads initially, but on fitting the diff to the casing I had an 'oh my god' moment: capheads catch the diff casing. So hexheads it is. BSF bolts are not ideal, if only from a supply point of view, but with these crownwheels, I am stuck with it. I dont think tightening them harder by 25% would make them break, would you? In the case of new custom bolts, the best would be to have the shank as short as possible. This allows the threaded part more stretch wich decreases the tendency to come undone. This might also be the clue with the p38 bolts. I think friction is really what keeps them together and the fully threaded bolt is the best in stretch. My plan currently is to use loctite, tab washers from a s3(or 2) and schnor washers and give them 25% more welly. To be continued.... Daan Quote Link to comment Share on other sites More sharing options...
will_warne Posted January 21, 2007 Share Posted January 21, 2007 Only one year of actual use though, Chris Oi!!! Before I took it off the road this time the longest it ever sat in the workshop was a week Quote Link to comment Share on other sites More sharing options...
LR90 Posted January 21, 2007 Share Posted January 21, 2007 IIRC KAM started selling stronger bolts to try and solve the problem. That's my understanding too. Worth giving them a call Daan Quote Link to comment Share on other sites More sharing options...
Andy Posted January 21, 2007 Share Posted January 21, 2007 i had both of my crownwheels come loose after fitting my lockers. i'd used locktite & cleaned the threads, they where the original bolts though. my current plan is if it happens again im getting those lockwashers series diffs had (or making my own) as i trust a mechanical solution much more than some fancy glue. Quote Link to comment Share on other sites More sharing options...
Tonk Posted January 22, 2007 Share Posted January 22, 2007 mine are fitted with locktabs, never had a problem Quote Link to comment Share on other sites More sharing options...
Daan Posted January 22, 2007 Author Share Posted January 22, 2007 mine are fitted with locktabs, never had a problem Sounds like the way to go then. Are these s3 or s2? Cheers, Daan Quote Link to comment Share on other sites More sharing options...
reads90 Posted January 23, 2007 Share Posted January 23, 2007 Daan, these are all of the guys I know who have KAM 4.75s (seem to be badly affected due to the width of the crownwheel).[*]Ali Read had this happen - diff was rebuilt and no issues when vehicle was sold about 18 months afterwards. IIRC KAM started selling stronger bolts to try and solve the problem. It was not 18 months later , it was about 2 months later i sold it But went again 2 weeks after i sold it Quote Link to comment Share on other sites More sharing options...
Tonk Posted January 23, 2007 Share Posted January 23, 2007 Sounds like the way to go then. Are these s3 or s2?Cheers, Daan i got mine out of a ser 2a diff, i think ser3 didn't have them Quote Link to comment Share on other sites More sharing options...
Daan Posted January 23, 2007 Author Share Posted January 23, 2007 That's my understanding too. Worth giving them a call Daan Eh.... yes the website mentioned them, and yes I ordered them. Then wondered where they are. Phoned back and the reply was: We never had BSF bolts, but we can get them for you; 2.30 pounds ech, which is fine, but: minimum order 2000.... i got mine out of a ser 2a diff, i think ser3 didn't have them Now ordered, cheers tonk. Quote Link to comment Share on other sites More sharing options...
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