Jacking rear of car uner diff

[Calaber]

Recently, I had the rear tyres replaced on my car. The young bloke who did the job ran the jack under the rear of the car and proceeded to place it under the diff, then jack the the car up. I didn't see him doing it until I noticed the car was off the ground and the jack was under the rear. I immediately told him that was incorrect and the diff centre was not the proper jacking point for an IRS Holden. I said I didn't want the diff carrier bent and that the factory manuals says not to use the diff as a lifting point. I asked him to drop the car back to the ground and use the sill lifting point.

He said he has always done it his way, but I told him what I wanted, so he did as I asked.

Now, has anybody else had problems with their diff carrier because of incorrect jacking procedures by garages, or was I being a bit precious? Is it safe to jack the rear by using the diff centre as a lifting point or not? I've always used the sill and will continue doing so, but I would have thought a tyre fitting business would be more careful and aware of the correct jacking procedure for such a common model of car.

[walesy]

my currant car is too low to get to the diff center with a big enough jack, but I have always used the diff center to jack up the rear of a car then put stands under the car, its just easier and ive never had any issues doing it

[Adds_05]

i wasnt aware the manual says that,ive always lifted the rear of my irs cars with a jack under the diff,seems to be ok,what business was it for interest sake as you'll find that nearly all tyre shops do that?

[Calaber]

I won't nominate the business - he's only a small trader and has been very fair with his prices. It was one of his staff who I dealt with. I mentioned it to the owner and he said he would talk to the fellow.

I have had a look at my workshop manual (Ellery's) and it refers to jacking the rear up under the diff then placing the car on stands, so perhaps I have misread this item somewhere, but I was sure I had seen a warning in a genuine shop manual some time ago stating that the diff was not to be used as a jacking point. This made sense to me because the diff cradle has a propensity to crack and it's not designed to take the whole rear end weight of the car in the centre - that job is for the outer mountings of the cradle, near each wheel arch, where the suspension arms are pivoted from. When the car is on the ground, its weight is distributed at the back between the two tyres and the weight is transmitted directly into the subframe structure by the design of the cradle. By jacking it up in the centre, the complete weight of the rear of the car is focussed on the cradle, but not below its inner mounting points. In my thinking, the concentration of the weight in an area where the cradle could be damaged by bending, could eventually lead to the cracking that the cradles are known for.

I might be wrong - it seems others here use the diff for jacking, but I'll stick with the sill locations.

[walesy]

yeah that does make sense calaber, spose its up to you, its your car and i spose we all do things in different ways

[VYMAD]

I can see your point, Calaber, but I found out off this forum that it was ok to jack up the rear of the car off the diff. Before reading that on here, I would NEVER have done so. Since then I've done it a few times and hasn't caused a problem.

[Calaber]

I'm damned sure I've seen a workshop manual which has the jacking points highlighted and states clearly that the IRS diff is not to be used. It was quite a while ago, and ever since I bought the VY over three years ago, I've always jacked it up using the sills. It would be interesting to see if there was any sign of bending or other damage on the cradles of cars that have been regularly lifted under the diff. Have any of you guys who jack the car up that way, ever had to replace the cradle and perhaps just put it down to metal fatigue?

[Adds_05]

vt onwards had very strong cradles that very rarely crack from what ive read,its more so vn-vs that crack ands its usually from giving it a hard time,burnouts etc

[VYMAD]

Well, like I said, only done it a few times, with no apparent problems. I, too prefer to jack under the sills even with a trolley jack.

[IBLOWN]

I always jack mine up at the diff. IRS too.

Been doing it on the same car for 12 years lol.

[edals]

Iv Always used the Diff, on the VR, VX & VY, No dramas at all

[HoZy]

Hahahahahahahaha

[walesy]

Hahahahahahahaha

you ok hozy?

[colgf]

If you want to risk damage to tailshaft, damage to diff mount rubber,damage to overextended axle half shafts & universals, damage to diff casing, damage to diff rear cover & oil seal causing diff oil leaks, damage to pinion front oil seal; sure go ahead!!!! My advice is NEVER jack an IRS vehicle by the diff.

[Reaper]

Same - jacked commodores up under IRS diffs for as long as they have been around with no ill effects.

Reaper

[Jonno]

its how i was taught to jack the rear up at trade schoool

[Murdoch]

If you want to risk damage to tailshaft, damage to diff mount rubber,damage to overextended axle half shafts & universals, damage to diff casing, damage to diff rear cover & oil seal causing diff oil leaks, damage to pinion front oil seal; sure go ahead!!!! My advice is NEVER jack an IRS vehicle by the diff.

How do you figure this?
You are not going to over extend half sharfs jacking from the diff cradle. The wheels will drop to their maximum irrespective where you jack it from at the back, even at the designed jacking points.
Its not going to move the tailshaft either? Its fixed to the diff, which wont move when jacking?

[STEALTHY™]

Alllllllllllso always use the diff to jack the car up (quicker for changing 2 tyres at once). Never had any issues with damaged parts as a result. Also never even heard of it being an issue until i read this thread.

[TrikkBen]

Fail thread... Diff is the only place I ever jack any of our cars up. The diff would have to be one of the strongest points in a car, The manual your recalling would have been written buy some soft #### in an office, The sill points are only there so numptys in suits who have no trolley jack can change a wheel.

[Surfwagon]

Same here never had a problem jacking up under diff
The car glovebox manual talks about using the jacking points on the sill but they are talking about using those stupid breakdown wind up scissor jacks because in reality how many people carry a trolley jack in their boot in case of a flat tyre.
Also in regards to using sill points how many people use the proper spacer block between the jack plate and the welded ridge on the sill.
Most older cars you look at have flattened sills from not using the proper spacer.

[SuperSixty6]

Pj,

I thought we agree'd to stay off this Forum? For the reason being non other then the replies you have got so far! :-p

I have had any issues myself, As states above it's a heap easier when changing both wheels (Trolley jack).

[Chrisvyss]

If you want to risk damage to tailshaft, damage to diff mount rubber,damage to overextended axle half shafts & universals, damage to diff casing, damage to diff rear cover & oil seal causing diff oil leaks, damage to pinion front oil seal; sure go ahead!!!! My advice is NEVER jack an IRS vehicle by the diff.

Thats interesting because the diff housing does not move up if you jack off it as its attached the car however using the sills the drive shafts drops down affecting all thats mentioned, as the cars weight is already on that point. My bests mates sons both holden trained mechanics and they say no issue so i go qwith them.

[Surfwagon]

I've seen a car (thankfully not a coomodore) fallen off stands when some one jacked up one side using the sills, placed stands under one side and went around to the other side and as the car lifted the car slid sideways.
Luckily for the guy the jack handle sticking out jammed against a wall but not before the head of the jack had slid towards the centre of the car crushing the sill which was now bent it inwards.
Even if he had fitted wheel chocks the car still would have gone sideways but this won't happen if jacking up the car by the each end with chocks fitted to the opposite end wheels.