hey im new! (4x4 info please!)

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inferno
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hey im new! (4x4 info please!)

Post by inferno » Wed May 10, 2006 10:45 pm

ok im tom and im from essex. i work for bx spanners, however nothing i do on here should be linked to the business as its not mine!

my latest project is to fit bx 4x4 transmission to a 309 gti, initially without the hydro suspension.

id like to know more about the bx 4x4 box, im collecting a complete doner car but have been advised that its likely to blow in no time at all!

however looking at the suspension set up on the bx4x4, it applies even power under acceleration btween the wheels due to the anti dive system. now im wondering if this could be the cause of the gearboxes front wheel drive going bang? and therefore would having normal suspension increase the life of this box and allow for my to fit a 2litre turbo engine?!

i know this isnt strictly bx, but this is my last hope of getting the info on the rare 4x4!

any info/opinions would be great! thanx!

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Post by ed4ferrets » Wed May 10, 2006 10:56 pm

I'm not the 4x4 buff you're looking for, just wanted to welcome you to the club :lol: :wink:
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Philip Chidlow
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Post by Philip Chidlow » Wed May 10, 2006 11:10 pm

BX Spanners in Essex??.. Nowhere near Chelmsford are you? Oh, and welcome to the Club. Good luck with the project.
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inferno
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Post by inferno » Wed May 10, 2006 11:13 pm

yes bx spanners in essex... nazing/harlow/hoddesdon area, about 45 mins from chelmsford mate, and what the hell,,, we have a lot of breakers i listed a few in for sale!:P

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Philip Chidlow
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Post by Philip Chidlow » Wed May 10, 2006 11:17 pm

I assume you do BX servicing and oily stuff then? I have a couple of things I'd like sorted this year. I'm down to one car at the moment so the big question is do you have a courtesy BX? :lol: :lol:

PM contact details and I'll give you a call,

Phil.
• COMING SOON... 1992 Citroen BX TZD Turbo Hurricane
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DavidRutherford
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Re: hey im new! (4x4 info please!)

Post by DavidRutherford » Wed May 10, 2006 11:29 pm

inferno wrote:it applies even power under acceleration btween the wheels due to the anti dive system. now im wondering if this could be the cause of the gearboxes front wheel drive going bang? and therefore would having normal suspension increase the life of this box and allow for my to fit a 2litre turbo engine?!
The suspension has nothing to do with the gearboxes breaking. The problem is a weak gear-pair. It used teeth that are too fine, and these strip fairly easily. A classic case of "down-to-a-cost" rather than "up-to-a-standard" (fine teeth are cheaper and easier to manufacture than coarse ones)

Very good luck indeed fitting BX 4x4 running gear to a 309 shell. That will require a massive amount of modification, including fitting a transmission tunnel, completely revised rear suspension pick up points, revised front suspension arrangement, bulkhead modifications, etc.etc.etc.

It does beg the question as to why fit the running gear to a 309? Why not just enjoy it in it's "correct" location.

And why even use BX4x4 running gear.... when the 405 MI16 4x4 is stronger. (but still won't drop straight into a 309 shell)
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inferno
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Post by inferno » Wed May 10, 2006 11:48 pm

Very good luck indeed fitting BX 4x4 running gear to a 309 shell. That will require a massive amount of modification, including fitting a transmission tunnel, completely revised rear suspension pick up points, revised front suspension arrangement, bulkhead modifications, etc.etc.etc.

It does beg the question as to why fit the running gear to a 309? Why not just enjoy it in it's "correct" location.

And why even use BX4x4 running gear.... when the 405 MI16 4x4 is stronger. (but still won't drop straight into a 309 shell)


ok im doing it this way as i have a rotton 4x4 in running order coming my way. i also have a 309 gti i was about to turbo with a xantia activa engine.however i am building a 16v turbo engine and from the driving experiences ive had in my astramax(2litre 4x4 turbo 300ish bhp) and my citroen zx(2litre 8v 6speed 170ish bhp) i cant see the power being usable. so im looking for a 4x4 setup.

im also a welder fabricater, cars have only recently became my job, always were a hobby. so im confident i can mod the gti subframes and rear arms to accomadate the drive train. the hydr suspension may be added at a later date.

surely if just one part lets the box down i could have a new part machined in stronger material?

And with regards to the courtesy bx... im afraid we dont!!!
we normally lend out the bosses astra :P however there is a nice bx 16 im waiting on that i suspect will be used for that purpose!

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Post by DavidRutherford » Wed May 10, 2006 11:59 pm

inferno wrote:so im confident i can mod the gti subframes and rear arms to accomadate the drive train.
Even Peugeot themselves couldn't do this. They used the complete rear suspension from the BX 4x4 in the back of the Pug 405 4x4. The rear hubs on the 309 GTi cannot be powered, and BX arms/hubs are very very different from 309 ones.

Considering that this box struggles with 120-ish BHP, I really do think you will have a very very expensive time trying to get anything more than that through it for more than about 20 miles.

Would be cheaper just to go and buy an Audi Quattro. And faster. And handle better.
Last edited by DavidRutherford on Thu May 11, 2006 1:19 am, edited 1 time in total.
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Post by Philip Chidlow » Thu May 11, 2006 12:03 am

Wouldn't it be better to find another BX shell? Or even do a Pug 4x4 to BX conversion? (Seeing as I know FA about all this, maybe I'd better stop fantasisng and leave it to the machine-smiths! :D ) Thank-you, And good night!
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inferno
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Post by inferno » Thu May 11, 2006 12:06 am

when theres a will theres a way;) putting a turbo engine in the bx is too easy... i like a challenge ;)

oh and i have a 309 beam that can be porewerd ;)

as i said my only concern is the weak box issue, i need an alternative... or details of the parts that give up... although i still see the wieght distrubution due to the anti dive must add to the power breaking probs?!

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Vanny
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Post by Vanny » Thu May 11, 2006 12:54 am

sorry, i told this mad man about the site, more fool me!

Tom and i had a discussion on this topic earlier, at length. We worked it out to this, the front transmission is known to be weak on the BX 4x4 stipping teeth on the power tranmission coupling. But why does the 405 4x4 transmission not fail? It doesn't have hydraulic suspension at the front for a start!

Now more than a few 4x4 tranmission systems that Tom and i know about fail when one wheel is turning faster than the other at the front or the front wheels are moving particulalrly quicker than the rear, loading the diff and causing damage!

So the front of the the 405 has normal sprung struts which compress under breaking, the BX hydraulic struts don't do this, theres more load and more weight so there is more force through the wheels presumably slowing them down at least a little. Front slow back not so slow, broken diff!

Its a theory!

Yes the 405 Mi16x4 has a rear hydraulic axel, but why? I put plenty of money on the real reason being cost, why make up a new rear sub and mounting and trailing arms and so on and so forth if your sister company already has all the gear made up (and probably in surplus amounts!).


I think every one here has some reason for loving the PSA vehicles? So why would i want to go buy an audi quattro (yeah, amazing cars) when i could have much more fun building something stupid and being able to gloat! Any body else managed to fit a Xantia pump and get rid of the bloody FD and had far too many people laughing all through the build? Didnt think so, i like a challenge, Tom deffinatley does! I'm collecting Xantia hubs and a full hydractive system shortly, and i've kind of sourced a HDi engine too . . . please someone stop me!

Anyways best of luck Tom, i still believe your a head job for trying, but as of yet no one i know of HAS tried to put any other engine onto the BX 4x4 system, has to be worth trying :D

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Post by DavidRutherford » Thu May 11, 2006 1:04 am

Vanny wrote:So the front of the the 405 has normal sprung struts which compress under breaking, the BX hydraulic struts don't do this,
BX struts do compress. If they didn't you'd have no suspension.

The suspension isn't the issue here... as it's not the diff that breaks, it's a gear pair that strip. Nothing to do with the diff at all.

The reason that 405 MI16 4x4 boxes are stronger is because they are not the same. The BX 4x4 and the 405 GL4x4 have open diffs all round, with a solenoid lockable centre diff. They have the weak gear pair, and they break.

The 405 MI16 4x4 has a Torsen centre differental, and a limited slip rear diff. No manual locks. The internals are stronger, and they don't break, even under the 160-ish bhp of a 405 16v
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Vanny
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Post by Vanny » Thu May 11, 2006 9:41 am

Your miss reading that again Mr R, UNDER BRAKING i said, if i brake really hard then does the BX nose dives the same way a sprung car does? Cos if thats the case my BX doesn't do that, in fact non of the BX's that i have raced on a track nose dive, hell with my dodgy rear suspension the back end drops not the front!


Theres also an insinuation that the gear pair has nothing to with the diff, nor the transmission, or even the engine, but since there all linked through the same part it must surely be possible that if the corners are travelling at different speeds then it might well be the huge load increase that strips the teeth and not just a heavy foot! I've seen many of these boxes that have supposedly stripped teeth, and when reconned thats always the problem, but the perceived cause has always been loading the teeth with too much torque in too short a time (ie dumping the clutch), but what if that ISNT the problem? What if the problem is that there is no play or room for slip within the diffs (which makes sence if the mi16x4 transmission doesn't fail decause of slip diffs), and this lack of play is what grinds off the teeth?

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Post by DavidRutherford » Thu May 11, 2006 11:32 am

The tiny difference between the front axle speed and the rear axle speed under braking is irrelevant compared to the difference in their speeds when going round a corner. The front axle takes a wider path around a corner, and hence travels further than the rear axle in the same time.

Which is of course only a problem if the centre diff on a BX4x4 is locked. If it is open, then the differential allows for this difference in speed in the same way that the single diff on a normal front wheel drive car allows for each front wheel having different speeds round a corner.

Yes, if the centre diff is locked, and you try and drive around a corner on tarmac, then the transmission will "wind up" with some fairly hefty forces generated because the centre diff cannot do it's job (very much like a series Land-Rover in 4wd mode... which has no centre diff, but that's another story)

But. As I understand it, the weak (fine toothed) gear pair which is the problem on a BX4x4 is between the 5-speed gearbox and the centre differential, and hence it will only see the torque generated by the engine. The 4wd arrangement can be wound up to breaking point, but this load will not be seen by anything "upstream" of the centre diff.
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Post by jeremy » Thu May 11, 2006 11:35 am

Anti dive suspension is a matter of steering goemetry, and broadly speaking is linked to the leading arm effect. if you drive a ZX or something with trailing rear suspension arms (like a BX) but with the handbrake on the back and stop it on a hill with the handbrake on - the back rises as the car rolls back. In reverse the trailing arm suspension functions as leading arms and holding the wheel produces a lifting force as the thing tries to rotate.

To produce anti-dive on the front the suspension is designed to function with a little leading arm effect - to counter the drop. Sometimes this manifests itself as some very strange wishbone angles (Rover P4 and 5 - P6 by a reaction arm?) and may be the reason why BMY struts point backwards. To be honest I don't think the BX has much - but do agree they don't dip much under braking - so it may be achieved by the braking force simply locking the strut by the application of excessive side force on the lower strut piston arrangement causing it to stick.

The hydraulic system plays no part at all in anti-dive as the volume of fluid ised to operate the back brakes is negligible and the height correctors take about 20 seconds or more to react (as when you sit in the boot with the engine running.)

My guess as to the cause of damage would be shocks transmitted down the transmission - principally caused by one wheel spinning then gripping and sending a shock down the transmission. From what David has said the Citroen system would use a conventional diff with a lock and the Peugeot uses a Torsen which I think relies on a Silicon gel or fluid for its operation and can provide some cushion.

With a conventional unlocked centre differential, if one wheel slips ALL the drive will go through it. If that wheel starts to grip (which can happen very suddenly) then tremendous force is applied to the transmission as that wheel snatches and transmits considerable force to the rest of the system. Not even Land Rovers take kindly to this treatment - but of course going slowly in mud is much less likely to damage the thing than full throttle starts on tarmac. (A bit of mud is quite kind to transmissions!)

If I wanted to go faster round corners I'd be looking at installing the passive rear self steering system as used on ZX and Xantia - it really is impressive on a ZX and does its job very well. Not as dramatic I agree - but probably more effective!