Badger_McLetcher
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| posted on 18/1/26 at 01:32 PM |
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Sierra LSD Modification?
Hi all, it's been a long old time since I've posted here!
I've got a bit of a conundrum I'd like some help with; I've got two diffs, a flanged 3.62 Sierra LSD and a push-in 3.14 Sierra
Open.
Is it possible to combine these into a flanged 3.14 LSD? If so what's the best way, and is there a workshop manual or similar I can
reference?
I've been trying to research this but can't seem to get a definitive answer. Experience has shown that while the AJ30 Jag gearbox is mostly
OK with the 3.62 diff, it's a little short at higher speeds. Given the torque to weight ratio, and how useless first currently is when
accelerating hard, I think the lower ratio would suit it.
Cheers all!
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gremlin1234
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| posted on 18/1/26 at 02:23 PM |
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might be easier to change wheel/tyre sizes?
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Badger_McLetcher
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| posted on 18/1/26 at 04:57 PM |
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Definitely an option, but ideally I'd like to keep the wheels I have on it for now- the bodywork is all built around them, and I figure I can
then use a wheel change in the future for fine tuning.
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Sanzomat
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| posted on 18/1/26 at 10:15 PM |
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I'd be interested to hear the definitive answer to this too. I was under the impression the crown wheel is thinner on the viscous LSD ones and
thicker on the open ones so not interchangeable but if the crown wheels are actually interchangeable then it opens up opportunities for me to put a
taller CWP in my 3.62 LSD with Lobros as I've found a 3.38 open one.
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roadrunner
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| posted on 19/1/26 at 07:04 AM |
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At the risk of looking stupid, what is the open diff.
I have a push in type 3.14 and would love to convert it to LSD.
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Sanzomat
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| posted on 19/1/26 at 11:16 AM |
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https://www.locostbuilders.co.uk/forum/9/viewthread.php?tid=204901
Looking back I found this thread. The post from Mcerd1 suggests all ford 7" CWPs are interchangeable. If that is correct, and no reason to doubt
Mcerd1, then I could get any 7" diff with the 3.38 ratio I want and transfer my viscous LSD and lobro stubs into that case without having to
reset the forward/aft setting of the pinion. I guess I could also put the open diff with my existing case and CWP to make an open 3.62 that I could
sell on to offset the cost of the 3.38...
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mcerd1
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| posted on 21/1/26 at 09:17 PM |
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^^ feels weird seeing me as the source 
I never ended up doing it myself - got too good a deal from one of the guys that was rebilding them for a living in the end (I think I paid for it
almost all of the work with otehr spare diff's and gearboxes pulled from scrap cars.... most of them are in Caterham S3's now  )
mine ended up just being a 3.92 LSD (I had 3.92 open and 3.62 LSD) nothing as fancy as a 3.14
But yes swapping over the CW&P set from a 7" to another 7" should be no big deal - but it will mean re-ajusting everything when you
build it
Also the bolt-on flanges for the LSD are different from open ones (this is also what stops you making a ford LSD with push-in shafts)
So as long as you keep the stubs with the centre they came from it should all work
- I did manage to get my hands on a copy of the workshop manual for rebuilding these diffs at one point, but it might just have been the 7.5"
version - if want a copy send me your e-mail on a u2u message and I'll see what I've got in the archives...
[Edited on 21/1/2026 by mcerd1]
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Sanzomat
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| posted on 21/1/26 at 09:40 PM |
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Thanks for the offer. I tried to u2u but it comes up with a "forbidden from this server" message. Odd as I know I've sent and received
u2u s on here before.
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mcerd1
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| posted on 21/1/26 at 10:05 PM |
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try just opeing this:
https://www.locostbuilders.co.uk/u2u.php
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roadrunner
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| posted on 22/1/26 at 07:27 AM |
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I've just seen on the MK site that a 7" 3.14 LSD for push-in shafts are selling for £2499
[Edited on 22/1/26 by roadrunner]
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Sanzomat
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| posted on 22/1/26 at 09:15 AM |
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quote:
Originally posted by roadrunner
I've just seen on the MK site that a 7" 3.14 LSD for push-in shafts are selling for £2499
[Edited on 22/1/26 by roadrunner]
I guess that is fully refurbed with new bearings and seals and a new Blackline ATB fitted but still shocking!
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MikeR
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| posted on 26/1/26 at 10:47 PM |
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I tend to suspect they double what ever price they get it in for - i've often seen things cheaper than their website.
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