bombero
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| posted on 8/7/16 at 09:16 AM |
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Sierra Diffs - Parts Swap??
I've got a 7" 3.92 LSD with Lobro shafts, fitted to my Westfield. I've been given a 7" non-LSD 3.92 with push-in shafts. My
questions are:-
1. Can I take our the 3.92 CWP and fit them to my diff?
2. Can I keep my LSD unit too, basically creating a 3.92 LSD with Lobro?
I don't intend to do the works myself but need to know the above so I don't make a right pudding of myself when speaking to a diff
engineer, lol!
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nick205
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| posted on 8/7/16 at 09:27 AM |
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Maybe worth a search on here or online, but can you not rebuild the driveshafts with Lobro CV one end and Tripod CV the other? May be a cheaper and
faster way for you to achieve what you're after. Rebuilding the CV joints is easy enough - peening the metal sleave over the Tripod CV joint is
a little tricky, but if you tackle the Lobro CV end it may be easier.
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nick205
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| posted on 8/7/16 at 11:02 AM |
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There's an LCB thread here on making "hybrid" driveshafts. Seems important to make sure you have the right driveshafts first though
WRT Ø for joint fitting.
http://www.locostbuilders.co.uk/viewthread.php?tid=204701
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fregis
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| posted on 8/7/16 at 09:03 PM |
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another option use 4x4 drive shaft ends.
ford sierra 4x4 without abs have lsd, lobro with bolts, and drum brakes - difference is part near wheel
but hard to find
[Edited on 8/7/16 by fregis]
Never be afraid to do what you are insolvent, remember: amateurs built the ark - Professionals built the Titanic.
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bombero
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| posted on 8/7/16 at 10:49 PM |
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Thanks guys....seems a bit more to this than I expected :-/
[Edited on 8/7/16 by bombero]
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mcerd1
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| posted on 12/7/16 at 11:11 AM |
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quote:
Originally posted by bombero
I've got a 7" 3.92 LSD with Lobro shafts, fitted to my Westfield. I've been given a 7" non-LSD 3.92 with push-in shafts. My
questions are:-
1. Can I take our the 3.92 CWP and fit them to my diff?
2. Can I keep my LSD unit too, basically creating a 3.92 LSD with Lobro?
I don't intend to do the works myself but need to know the above so I don't make a right pudding of myself when speaking to a diff
engineer, lol!
Just to make sure I understand you
you've got a 3.92 LSD with lobro's and a 3.92 open diff with push-in's - ie they both have the same ratio ?
you want to use the CW&P from the open diff - I assume this means your current CW&P are damaged / badly worn ?
the key points are:
* all the 7" casings are effectively the same
* all the 7" CW&P sets can be used in any 7" diff - open, ford LSD or aftermarket LSD
* The viscous ford LSD's use unequal lengths of stub axles and for the 7" are only available as 100mm lobro / bolt-on ones
* All the aftermarket LSD's and open centre diffs use equal length stub axles, with snap rings for the push-in and circlips for the bolt-on
* it is possible to modify the open centre bolt-on stub axles to accept snap rings, allowing them to be used with aftermarket LSD's such as
quaife /tranx etc...
so how easy all of this is depends on what your current LSD is and which diff centre you ultimately want to keep.....
[Edited on 12/7/2016 by mcerd1]
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bombero
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| posted on 12/7/16 at 11:19 AM |
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quote:
Originally posted by mcerd1
quote:
Originally posted by bombero
I've got a 7" 3.92 LSD with Lobro shafts, fitted to my Westfield. I've been given a 7" non-LSD 3.92 with push-in shafts. My
questions are:-
1. Can I take our the 3.92 CWP and fit them to my diff?
2. Can I keep my LSD unit too, basically creating a 3.92 LSD with Lobro?
I don't intend to do the works myself but need to know the above so I don't make a right pudding of myself when speaking to a diff
engineer, lol!
Just to make sure I understand you
you've got a 3.92 LSD with lobro's and a 3.92 open diff with push-in's - ie they both have the same ratio ?
you want to use the CW&P from the open diff - I assume this means your current CW&P are damaged / badly worn ?
the key points are:
* all the 7" casings are effectively the same
* all the 7" CW&P sets can be used in any 7" diff - open, ford LSD or aftermarket LSD
* The viscous ford LSD's use unequal lengths of stub axles and for the 7" are only available as 100mm lobro / bolt-on ones
* All the aftermarket LSD's and open centre diffs use equal length stub axles, with snap rings for the push-in and circlips for the bolt-on
* it is possible to modify the open centre bolt-on stub axles to accept snap rings, allowing them to be used with aftermarket LSD's such as
quaife /tranx etc...
so how easy all of this is depends on what your current LSD is and which diff centre you ultimately want to keep.....
DOH and double DOH .. I've spotted a fundamental error in my original post, grrr!
It should read: "I have a 3.62 LSD with lobros fitted, and I've been given a 3.92 non-LSD with push-in" Question is, can I
take the 3.92 CWP and put them into my existing diff?
Apologies to all!
[Edited on 12-7-16 by bombero]
[Edited on 12-7-16 by bombero]
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mcerd1
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| posted on 12/7/16 at 12:02 PM |
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in that case yes no problem - swap to any 7" ratio you like and keep the existing LSD and driveshafts 
all it should cost you is a set of seals and bearings along with the time to re-build and set it up
some places might even give you a few £ off in exchange for the spare bits (assuming you don't want them)
also just to check...
changing from a 3.62 to a 3.92 will give you an ~8% increase in the revs you need for any given speed & gear (or an 8% drop in speed for any given
revs&gear)
so if at 70mph your car currently sits at 3000rpm in 5th gear - then after changing to the 3.92 it'll sit at 3248rpm
or from another point of view if you find that you have to change from 1st to 2nd gear at say 30mph then you'll need to change at 27.7mph with
the 3.92 ratio
[Edited on 12/7/2016 by mcerd1]
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bombero
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| posted on 12/7/16 at 12:39 PM |
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Thanks mcerd1, very helpful! 
I did appreciate that there'd be an increase in revs at any given speed however, I hadn't an idea of how much so the % figure is a good
heads up for me. I'm researching into the swap in the hope of achieving quicker acceleration. I'm running an MT75 box is has a stupidly
short 1st gear, which will be unaffected by the potential swap (I'll just have to practice quicker/slicker gear changes, lol).
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mcerd1
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| posted on 12/7/16 at 02:56 PM |
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the % calc for any given ratio change is actually fairly simple
in your case its just 3.92 / 3.62 = 1.08 and multiply that by the original revs (or subtract 1.0 and multiply by 100 gives the +8%)
or the other way round if you want to know the drop in speed = 3.62/3.92 = 0.92 and multiply that by the original speed
of course if you want to save yourself the hassle you could just use a gear calc program like this one:
http://locost7.info/gearcalc.php
btw - I assume yours is the yellow one that I've seen in tesco car park a while back ?
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bombero
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| posted on 13/7/16 at 08:39 AM |
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quote:
Originally posted by mcerd1
btw - I assume yours is the yellow one that I've seen in tesco car park a while back ?
Ah yes it is! I see that you hail from the shire also!
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