Rear axle cracked

Idler Chris
Posts: 15
Joined: Sun Nov 01, 2015 10:51 pm

Re: Rear axle cracked

Post by Idler Chris »

" They can't do any harm". Only a qualified engineer who has done testing is qualified to make such a statement. The current bump stops where engineered by Isuzu I would not dismiss their abilities quite so quickly. I replaced the Isuzu bump stops with air bags which were claimed to be better but the axle housing still cracked. I may have been better off leaving the the original bump stops in.
goody59
Posts: 123
Joined: Fri Apr 25, 2014 2:12 pm
Location: Wollert ((Melbourne outer northern suburb)

Re: Rear axle cracked

Post by goody59 »

I don't need to be a qualified engineer to know that reducing shock load on axle as it grinds to a hault on the bump stop limit by having a progressive type jounce stop is a favourable preventative action to take. Just need common sense to know that, it is not rocket science imho. You see, I wouldn't of thought of replacing a bump stop with an airbag would be a sensible thing to do either.
Idler Chris
Posts: 15
Joined: Sun Nov 01, 2015 10:51 pm

Re: Rear axle cracked

Post by Idler Chris »

With respect, who has said that the product you espouse reduces the shock load better than the Isuzu bump stop? Where is the evidence that this product reduces the shock load, where is the test data? Replacing the bump stop with an air bag seemed like a good idea at the time, in hind sight it would appear that it was not the sensible thing to do.
goody59
Posts: 123
Joined: Fri Apr 25, 2014 2:12 pm
Location: Wollert ((Melbourne outer northern suburb)

Re: Rear axle cracked

Post by goody59 »

A progressive stop would reduce shock load compared to non progressive. That is common sense. I didn't design these jounce stops, Outback Armour did but as a consumer, I can see the benefit. As much as I love my Dmax I know it has short comings. That is why modifications are devised.
Isuzu engineers have failed to get a number of design ideas right on my MY18 model. Example is oem CV angle, the turbo charger, cracking inner guards and the "inadequate for task" suspension just to name a few. Blind Freddy can see that there is room for improvement in a number of areas without blind Freddy being an engineer or referring to test data to see.
mydmax
Posts: 1740
Joined: Sat Oct 12, 2013 8:36 pm

Re: Rear axle cracked

Post by mydmax »

This is as I see it.
It seems people think a GVM upgrade makes the vehicle more capable. All it is a spring set to hold up weight and hopefully provide suitable shock absorbers for the task of handling more weight than the vehicle was EVER designed to carry. The AXLE “has not been upgraded” and so if designed for it's purpose and then exceeded by load or terrain it may fail. The way they are made indicates there will be some flex beside the spring seat, and if used within it's design it probably won't give trouble. Repetitive flex cause fractures as we all know. The area IS an abrupt change of material section at the outer side of the spring seating. Higher stresses would be expected there, but if not exceeded no problem.
People presume a camper weight or additional load, after an upgrade means all OK, not so. The axle hasn't been improved, it is made to a weight, material thickness and strength.
OK, we are all loaded up near the MAX or over design weight claiming GVM increased ability and that usually means most vehicles now have less travel. Goody says 90mm ready to roll, a respectable clearance. On the road with same rear axle, upgrade or not, the now max load must be causing axle tube flex to some degree and then higher than design load hits the stops, the inertia of the large load will cause far more stress at crucial points than ever before or designed for. Because the weight is more, the actual force on the axle tube will be grossly over what it would normally get to. MULTIPLE Tonnes all acting on one area. Those rubber things simply act as a spring. Not sure they do much apart from apply force to the centre point of the chassis, but that is another story.
The shocker resistance and the forces associated with them is additional to the spring action, but ALL the forces are still at the area beside the springs where cracks appear. The wheel and distance to springs is a lever constantly trying to bend the axle t but don't remove any stress from where the axle tube fails. Some people help it fail with more flexing. GVM increase has no bearing on it at all, just makes it worse We are not judging the quality of the springs as they act differently with various designs.
goody59
Posts: 123
Joined: Fri Apr 25, 2014 2:12 pm
Location: Wollert ((Melbourne outer northern suburb)

Re: Rear axle cracked

Post by goody59 »

All fair comment Mydmax. I don't plan on exceeding the 3050kg oem GVM by much as I agree that areas of vehicle like axles, bearing, drive components and brakes are not upgraded with GVM upgrade but I wanted to be legal Australia wide and no where near my allowable new GVM of 3600kg. I will add these Outback Armour jounce stops because I see merrit in them. I will and do keep an eye on undercarriage for signs of stress and failure of components. I don't tow. I plan to tour versus harsh off road work. The Dmax is good but not perfect. I know that. Thanks for input on issue. I am aware of axle housing failures and most of the other Dmax issues. Aware but not alarmed.
mydmax
Posts: 1740
Joined: Sat Oct 12, 2013 8:36 pm

Re: Rear axle cracked

Post by mydmax »

Goody
I hope these are not the units you are considering fitting to your vehicle.
Rear Heavy Duty (2 per kit) OASU4210004
Rubber, extended, progressive rate.
Highly recommended for vehicles with heavy rear loads.

Specifications Details
Size: 110mm x 55mm
Design: Extended-Progressive rate
Don't you think the 110mm length will already be filling the gap which you have, and so the units will be immediately under compression at the outset. Therefore acting not a a bounce rubber but as a rubber spring. It surely will make the suspension ride harder and as it states, they are progressive. Sounds nice but don't you require compliance to ABSORB and not an ever increasing spring rate which will suddenly compress and stop somewhere in it's range and still place high impact loading to chassis. axle etc.
goody59
Posts: 123
Joined: Fri Apr 25, 2014 2:12 pm
Location: Wollert ((Melbourne outer northern suburb)

Re: Rear axle cracked

Post by goody59 »

The 110mm length jounce stop replaces the oem bump stop that is about 80mm at a guess in length so another 30mm of progressive compression section. I can't see the problem but I will get under with a ruler and do the maths first. I will make further enquiries and look into it further first before doing anything though mydmax.
goody59
Posts: 123
Joined: Fri Apr 25, 2014 2:12 pm
Location: Wollert ((Melbourne outer northern suburb)

Re: Rear axle cracked

Post by goody59 »

Ok ruler out and under I went. The oem bump stop is 80mm from the bottom of bump stop mount plate to end of bump stop. Between top of bump stop to the contact plate of chassis a further 90mm. So 170mm between spring top and contact plate. Jounce stop 110mm in length so, if fitted, leaves 60mm between top of progressive jounce stop and contact plate of chassis before there is contact between the two. Plenty of travel imho for suspension to work on compression before the jounce stop comes into play.
mydmax
Posts: 1740
Joined: Sat Oct 12, 2013 8:36 pm

Re: Rear axle cracked

Post by mydmax »

Goody
Today I took my camera and went hunting. Found a Dmax with OE rubbers and it looks to me as though if they were compressed to solid on upward compression the amount of travel BEFORE that will be far more than a Higher bracket 110mm rubber thingo. I would want to know what dimensions the "jounce" units are when fully solidly compressed. Overall it would be greater height than the OE rubbers and so might be actually reducing upward travel. I then went to Aldi, For the savings of course, and saw a Dmax there, Happened to be my ex wifes brother inlaw. Had a look see, and he has had fitted a thick factory bracket with a twin bellows airbag which ALSO has an Upper thick bracket. Although it may hold the vehicle level, ie same ride height with 2.7ton van, the amount of actual upward travel is far less than having springs hold that height and OE rubber units. Therefore with aftermarket springs holding it higher for the load, ie where you want it to be, and everything else OE, you would have a better suspension. If quality shocks to control weight and suspension action are fitted it then should be quite acceptable. I tried to explain to him the limitations of what he has had fitted but the same perceived benefit is in his mind. He obviously is sticking to what the seller of airbags has told him. One look and it is plain there CANNOT BE any decent rubber cone system at full compression of the small amount of upward he now has when the bags are fully compressed, but thinks it is superior to OE distance.
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