IIA 88 front prop clearance

[Johnno1969]

Hey folks,

I am a little concerned about the clearance between the front propshaft and my brand new crossmember. A mate fabricated the new member and was pretty meticulous with his measurements - but now with everything in place it looks a little too close for comfort. The old (very rotten) crossmember did not have a cutaway for the prop, and in photos (though no two are from exactly the same angle) the two crossmembers look damn close - but there is not much clearance now. It is about 30mm at the trailing edge of the crossmember (closest to transfer case flange). At the leading edge, it is around 6mm. These measurements are taken with the chassis jacked up and the road wheel, spring and axle left to hang by their own weight. The engine and transmission are in the vehicle, but no bodywork is fitted.

I'd expect that in driving conditions, sudden shocks could cause the suspension to drop suddenly and the springs flex downward.... so it seems to me that the prop will likely strike the crossmember the way that it is.

I will attach some photos. I'd appreciate any thoughts. Apologies that the photos are not dead square-on. Hard to get the SLR in there...

Cheers,

John

[Johnno1969]

What happened to the bleeding photos? They were attached when I previewed the post. Trying again....

Clearance, front prop I.jpg (http://www.aulro.com/afvb/attachment.php?attachmentid=47241&stc=1&d=1337997218)

Clearance, front prop II.jpg (http://www.aulro.com/afvb/attachment.php?attachmentid=47242&stc=1&d=1337997427)

[Warb]

If the chassis is supported and the axle is hanging free, then how much more travel is left? On the front, the shocks provide the limit to downward movement, so if they have already bottomed out there is no more. If not, can you add weight to the axle (or lever it downwards) and check whether there is any clearance at maximum axle droop?

[Johnno1969]

If the chassis is supported and the axle is hanging free, then how much more travel is left? On the front, the shocks provide the limit to downward movement, so if they have already bottomed out there is no more. If not, can you add weight to the axle (or lever it downwards) and check whether there is any clearance at maximum axle droop?

The clearance between the prop and the crossmember is as described in the first post, with the travel finished. Thanks, I will lever a bit on the axle to see if I can increase the travel downwards. There are no shock absorbers on the axle; at present the vehicle is a rolling chassis. The thing is, there is bugger-all difference in the clearance with the axle either carrying weight or hanging. I'd like to think that with the vehicle assembled, the clearance would increase....but the heaviest item - engine and transmission - is already in place.

Cheers,

John

[Warb]

You may well find that the springs won't compress to the normal ride height just by lowering the vehicle. The interleaf friction will tend to make them stay where they are, until enough weight is added to make them move. However, that doesn't matter if there is still clearance at the bottom of their travel! Whether it's 5mm or 500mm clearance doesn't really matter.

My Delco catalogue lists the open length of the front shocks as 437mm, which I'd assume is eye to eye. Measure between the two shock mounting bolts/pins, and if that distance is more than 437mm then you are at maximum travel, unless you have longer shocks!

[Johnno1969]

Thanks very much for that advice. It's what I have been rather hoping to hear! I would rather not have to take the grinder to the nice new crossmember... I will still get a crowbar and see what I can do with levering the axle downward, just to be sure. Last thing I would want is for the suspension to drop on a rebound and bring that prop up hard against that crossmember. It would be interesting to hear from anybody else who has a IIA shorty and hear how much clearance there is in the same spot on their vehicles.

[Warb]

I've just been out to the other shed to use the press, and had a quick look around. My '68 SWB farm vehicle, at rest, has about 10mm of clearance between the propshaft and the leading edge of that crossmember (but with no rubber in the bushes and worn springs, the axle is probably higher than it should be, i.e. "extra" clearance). A SIII LWB that somebody has fitted with home-made extended shackles has perhaps 15mm, and a LWB IIa that may have originally been a 6 cylinder has at least 40mm, though it appears to have a much deeper "drop" on the cross member.

But the '68 SWB is much the same as yours.

[Johnno1969]

My Delco catalogue lists the open length of the front shocks as 437mm, which I'd assume is eye to eye. Measure between the two shock mounting bolts/pins, and if that distance is more than 437mm then you are at maximum travel, unless you have longer shocks!

The distance between the two shock mounting pins on my vehicle is 442mm, which would seem to be good news. Thanks for having a look at your vehicles too, mate. Much appreciated.

I think I will see what it settles to with the vehicle reassembled before I make any decisions to go cutting into anything. Trouble is, by then it'll be all rebuilt!

One thing that has occurred to me is that, by the book, the prop is meant to be fitted with the yoke (splined) end down near the diff. If I reversed it (which is the way I have always used/seen front props on Defenders) it would effectively increase clearance over that crossmember.

[JDNSW]

The distance between the two shock mounting pins on my vehicle is 442mm, which would seem to be good news. Thanks for having a look at your vehicles too, mate. Much appreciated.

I think I will see what it settles to with the vehicle reassembled before I make any decisions to go cutting into anything. Trouble is, by then it'll be all rebuilt!

One thing that has occurred to me is that, by the book, the prop is meant to be fitted with the yoke (splined) end down near the diff. If I reversed it (which is the way I have always used/seen front props on Defenders) it would effectively increase clearance over that crossmember.

The only reason for having the sliding joint at the front is so that dirt etc is not forced into the joint by vehicle motion. But if the clearance is as you say, and there are no shock absorbers fitted, I don't think you have a problem. You don't have to finish the vehicle and then check - just fit the front shock absorbers. What is critical is the maximum extension, not the clearance at rest, and, as pointed out above, the maximum extension is limited by the shock absorbers.

Another point to check - I assume all engine and gearbox mounts are in good condition. But even in this case, there is a certain amount of slop in the attachment holes of these, and it is possible that the engine/gearbox has a slight lean to the right that can be corrected by loosening everything, jacking up the RH side of the transfer case, and then retightening everything. The weight of the transfer case is likely to have ensured that all the slop was taken up in the right hand down side if you were not thinking of this.

John

[Johnno1969]

Another point to check - I assume all engine and gearbox mounts are in good condition. But even in this case, there is a certain amount of slop in the attachment holes of these, and it is possible that the engine/gearbox has a slight lean to the right that can be corrected by loosening everything, jacking up the RH side of the transfer case, and then retightening everything. The weight of the transfer case is likely to have ensured that all the slop was taken up in the right hand down side if you were not thinking of this.

John

Hey John,

Thanks very much for your points. I will be tidying up how the engine and transmission sits on the mounts and see how things rest after that. I do tend to think it'll all be fine, but it's certainly been worth throwing out the question to the brains trust.

Thanks,

John