Series 3 Parabolic Problems

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Kiwi Landie said:
Hi All

Tottot is correct - I have given this a lot of thought - but necessarily so in my view. Things are clearly amiss at present. I cranked up a decent push down on the front of the chassis last night and can confirm that no amount of loading is going to correct the mismatch such that the standard prop will fit without it being stretched out to the max.

David - I have a standard 2.25 engine and box.

Nick - Yes the locator dowel sits nicely in the middle of the U bolt plate hole on both sides.

By my measurements and by comparison with a set of standard springs, the dowel in the centre of the GME springs is too far forward by about 20-25 mm. The springs I have are symmetrical so cannot be mounted 'wrong way around'. My proposed solution was to simply redrill the hole in the bottom spring plate (the one the U bolts go through). This having the effect of sliding the axle backwards along the spring, so it is in more or less the correct position. I agree that drilling the springs themselves is not a good idea at all.

I agree that having the axle a little forward of the bumpstops is not a bad thing when the vehicle is static and lightly loaded - the axle will tend to move back a touch as the springs flatten out under load. However, by measurement, even if the spring is flattened right out, the locating dowel (and hence the axle in its current setup) is still well forward of the bumpstop position. This (in my mind anyhow) has to be incorrect. After all, 35 mm is half the length of the bumpstop. I could see 10 or even 15 mm offset being beneficial, but not the amount I have.

I also agree that having a propshaft that is not in (roughly) the middle of its slip length when the vehicle is static will eventually end in disaster. Hit a bump and you will push hard on the transfer case, go over a hole and the prop will fall apart.

So - the question is - is the dowel position in my springs incorrect? I have measured the chassis against another truck and the key dimensions are identical so I don't believe my chassis has been modified.

If the dowel is wrong, is there fundamentally a problem with redrilling the U bolt plate to slide the axle backwards a bit?

I have asked Paddocks for their opinion on the springs. Not heard anything yet and am not overly hopeful of inspiration from this quarter. I may be wrong though.

I'm reluctant to chase down a longer prop if my suggested modification will work.

Thanks all for your input thus far.
Click to expand...
 
Kiwi Landie said:
Hi All

Tottot is correct - I have given this a lot of thought - but necessarily so in my view. Things are clearly amiss at present. I cranked up a decent push down on the front of the chassis last night and can confirm that no amount of loading is going to correct the mismatch such that the standard prop will fit without it being stretched out to the max.

David - I have a standard 2.25 engine and box.

Nick - Yes the locator dowel sits nicely in the middle of the U bolt plate hole on both sides.

By my measurements and by comparison with a set of standard springs, the dowel in the centre of the GME springs is too far forward by about 20-25 mm. The springs I have are symmetrical so cannot be mounted 'wrong way around'. My proposed solution was to simply redrill the hole in the bottom spring plate (the one the U bolts go through). This having the effect of sliding the axle backwards along the spring, so it is in more or less the correct position. I agree that drilling the springs themselves is not a good idea at all.

I agree that having the axle a little forward of the bumpstops is not a bad thing when the vehicle is static and lightly loaded - the axle will tend to move back a touch as the springs flatten out under load. However, by measurement, even if the spring is flattened right out, the locating dowel (and hence the axle in its current setup) is still well forward of the bumpstop position. This (in my mind anyhow) has to be incorrect. After all, 35 mm is half the length of the bumpstop. I could see 10 or even 15 mm offset being beneficial, but not the amount I have.

I also agree that having a propshaft that is not in (roughly) the middle of its slip length when the vehicle is static will eventually end in disaster. Hit a bump and you will push hard on the transfer case, go over a hole and the prop will fall apart.

So - the question is - is the dowel position in my springs incorrect? I have measured the chassis against another truck and the key dimensions are identical so I don't believe my chassis has been modified.

If the dowel is wrong, is there fundamentally a problem with redrilling the U bolt plate to slide the axle backwards a bit?

I have asked Paddocks for their opinion on the springs. Not heard anything yet and am not overly hopeful of inspiration from this quarter. I may be wrong though.

I'm reluctant to chase down a longer prop if my suggested modification will work.

Thanks all for your input thus far.
Click to expand...
No Kiwi.....not talking about the in the U bolt mounting plate hole....you cant see this one when the axle is sat on the spring.

Much more important.....on the top side of all of the springs is a round bolt head.....this round head has to sit inside a lug or hole on the flat mounting face on the axle body....easy to miss it.....if the axle sit incorectly....it will sit either forward or to the rear.
 
Ah - ha! Now we're talking. Yes - I remember that now from when I put it all together and look back at the photos. Yep - that lug is definitely located inside the corresponding 'socket' on the bottom of the axle.

This is the kind of advice that I was looking for - So - sliding the axle backwards on the spring is not as straightforward as simply redrilling the U bolt plate hole, I'd need to deal with this top mounting lug issue as well.

I'm thinking that this would be a much more difficult proposition.

That's a blow - I thought I was on to something there. Still - better to find out before I start pulling things to bits. Thanks a lot.
 
OK - a bit more to report here.

I got hold of GME. They were very quick to respond, but told me to go through Paddocks.

So - I hung out for a reply from Paddocks.

A day or two later I got an email asking for my front axle serial number. So I sent that. Next day I got an email saying that my front axle was off a Range Rover and as my car was clearly a hybrid, they couldn't help me further. They'd been pretty helpful up until that point though - to be fair.

Not sure how a Range Rover axle fits a series, but greater wisdom than mine may have an answer.

Suspecting that this was all a bit of a red-herring, I figured what I actually needed was max and min lengths of the prop gap front and rear.

So - armed with a couple of 2.5 tonne truck tie-straps I wound the springs up to the bumpstops, to measure the gap at full bump. I then repeated this at the rear.

I can assure you that winding up brand new parabolics to the stops is very hard work! It's also pretty scary taking the tension off again......

I hoisted the chassis up to obtain full droop and rear.

So I now have four measurements for the two propshafts:

Full droop: Rear = 580 & Front = 650
Full bump: Rear = 570 & Front = 600

On full bump, both axles appeared to be around 15 mm forwards of true bumpstop centreline, but there was plenty of contact, so I think this issue is less critical than I previously thought.

So I now need a couple of props that fit the above specs.
 
A RR axle is quite a bit wider in track than a Series.....with std wheel the would protrude outside the body line.....and of course the maybe evidence were the RR fitting have been cut of the axle.
 
It being a rangy axle would explain a lot. I had noticed the disc brakes but thought they were a conversion available for the series.
It is a lot of work to convert a coil spring axle to leaf and yours even has the axle tube stiffener found on HD vehicles.
As well as the wider track check the ball housing to axle bolts
Series axle has 6 bolts
Coil spring axle has 7 bolts.
 
None of the parts you list have any thing to do with the swivel housing Blackburn. I recon it is a series axle with disc conversion fitted Kiwi has.
 
Only six bolts each end of my axle. It doesn't look as if it has been modified, but without anything to compare it with, it is difficult to be certain.

If it is a Rangie axle, does anyone know if the differential is different from a Series? To my way of thinking, the length of the diff nose would be the only variable which would change the length of the propshaft, which is the key issue that I am now trying to solve.

Either way - it does look as if I need a slightly longer prop at the front, and can just about manage with a standard rear.

Cheers
Andrew
 
Rangy diff and series diff same on the outside. Different gear ratios though.
Your series axle has been modified, no series had discs as standard.
 
Yep - I fitted the Heystee disc setup and threw away the drums.

As far as I can tell - my axle is the same as all of the books/Internet photos, with the exception of the strengthening piece on the bottom edge of the passenger side.

Certainly the diff looks the same as the Series illustrations, and when I had it to pieces and counted the teeth - the ratios are standard Series.

So - I cannot account for the apparently Rangie serial number, but like I said a few posts back - I think this is a red herring. Maybe it was also an export serial number?

Cheers
 
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