Jump to content

Wobbly back end


Recommended Posts

Just received a couple of sets of Mill Services lifters today, different sizes to give me a choice of what to do with the back end of the 90 to restore some altitude. Good timing as it is a public holiday here tomorrow, to remember the Navy beating the Germans 2200-6 a few years back (and we thought 5-1 was good...)

I know that 2" or more of lift at the front can give propshaft vibrations (as I found out...) but what are people's experiences at the back? I have 2 sizes of lifters 1" and 1.5", plus the rubber isolator rings which add another 0.3" approx so 1.3" or 1.8". My feeling is that either is likely to be OK but I just wondered if anybody else has had prop vibrations on the back, or if it only affects the front? I haven't measured but I think the back prop is longer so presumably less of a problem. But still keen to avoid having the whole lot off several times as I did with the front :)



Link to comment
Share on other sites

Prop vibrations affect the back, just as much as the front.

They are mostly caused by the nose of the diff not being parallel to the gearbox drive flange.

The more out of allignment, the more vibration.

On the back however, it is easier to fix by putting shims between the radius arm and chassis bush (tractor washers are good for this). This causes the axle to rotate a bit and you can easily bring the two into alignment with no more than a selection of washers.

It has the added benefit that with the two parallel, the A frame ball joint is closer to the position in which it gives the greatest articulation.


Link to comment
Share on other sites

Thanks Si

I didn't really ask the question I was trying to ask (it was stupid o'clock when I did the original post!) :wacko:

What I meant to say :) was "at what height do prop vibrations start to become noticeable" - general feeling is 2" or so on the front, but what about the back... I think the rear prop is a bit longer so possibly slightly less sensitive to height changes than the front??

I have some measuring to do today of suspension deflection between the "empty state" and the "fully armed and ready to scramble state" which will affect the decision - I'm getting ready for my annual Christmas excursion to the land beyond the seas where be dragons :) and I don't really want to find I have an irritating wobble when I'm away from home and only have limited facilities to change anything around :unsure:

Interesting idea with the washers - what do you call a "tractor washer"? - presumably a washer off a tractor! - but what would it's original function have been?

You must get some ferocious prop vibrations when you crank your air suspension up to +15"?!

Link to comment
Share on other sites

I decided to try the bigger ones first, so have put the 1.5" on.

Bluddy excellent! No prop problems, and the other thing I was worried about - topping out the shockers - isn't happening either, I went for a rather-too-fast charge down a very rough track for about 1 mile or so, to get a photo I shall post up later before the subject matter disappeared, and no problems at all - in fact I reckon it is now probably the most comfortable 90 I have ever driven over rough ground - combination of retaining the std (relatively soft) springing, adding gas shocks to keep it under control, plus a lift at both end to stop saying "hello" to the bump stops - and you can charge along at an indecent speed without hitting top or bottom of the travel.

Highly chuffed B)

Roll on Christmas :)

Link to comment
Share on other sites

Monroe Adventurers - got them from Bearmach, good price too (though we deal with them at work so get trade prices - not sure what they retail them at but they were F cheap!!)

The fronts are noticeably stiffer than the std (good condition) LR ones I took off, the rears are a bit stiffer but not too much. Just spot on - really chuffed with them and achieved exactly what I wanted. Also, and this is quite important for here, they have proper metal stone guards on the pistons not some rubbish plastic boot - using the vehicle on gravel roads with lots of stones pinging around at speed underneath, you really don't want exposed pistons!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy