djtom
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| posted on 15/7/09 at 12:27 PM |
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Sierra diff driveshaft diameter?
Quick question - are there two types of push-in Sierra driveshaft? The measurement that I need refers to the splined section that pushes into the diff
itself.
I bought a Tran-X plated LSD from Ebay but my push-in shafts are too small in diameter to engage the splines within the diff. Speaking to Tran-X they
say that the diff is designed to replace a 7" non-lsd diff with push in shafts.
But that is what I have! Which leads me to the conclusion that there may be two different diameters for the push in part of the driveshaft, and my old
diff uses the small one, and my new diff uses the big one. Either that or I have just bought an expensive (but shiny and well-manufactured!)
paperweight.
Anyone got any ideas?
Tom
[Edited on 15/7/09 by djtom]
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MikeR
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| posted on 15/7/09 at 12:39 PM |
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there are two sizes.
Normally you get the 'smaller' size. The larger size will fit into a normal sierra LSD with some modification / bits from the sierra LSD
diff (how to has been covered on here before).
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avagolen
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| posted on 15/7/09 at 12:40 PM |
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Hi Tom, I cannot give the dimensions, but a little support info. I have been reliably informed that there are 3 diff sizes. 6.5, 7 and 7.5 inches.
They all look similar but with minor external differences. 6.5 diff have a different size castings on either side for the drive shaft inserts when
viewed from the rear, the 7" have the same size castings and the 7.5" have the same as the 7" but with solid castings where the long
bolt goes through at the top of the diff to chassis. I would think that your old diff was 6.5" See pics of 7" diff.
Hi Tom I am getting in a mess with this replay. If you look at the diff from the rear, you should be able to see both of the castings for the
driveshaft insert castings. If you cannot, it is a 6.5 inch" diff. The castings should be about 0.5" deep. See photo in my archive titled
7"diff, rear view.
I still cannot get one on this post....
Cannot find the "attachment:" button.
[Edited on 16/7/09 by avagolen]
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djtom
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| posted on 15/7/09 at 01:12 PM |
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Thanks guys. Doing a bit more research, it looks as though at least one other person has had this problem:
http://www.locostbuilders.co.uk/viewthread.php?tid=95460&page=1
avagolen - can you expand on which part of the casing differs from side-side on the 6.5" diffs?
Anyone else got any info on how to positively identify a 6.5" diff? Does this measurement refer to the dia of the crownwheel and if so, which
part exactly? OD. ID or PCD?
Thanks,
Tom
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matt_claydon
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| posted on 15/7/09 at 01:24 PM |
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See my posts here:
http://locostbuilders.co.uk/viewthread.php?tid=113835
and:
http://locostbuilders.co.uk/viewthread.php?tid=108845
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djtom
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| posted on 15/7/09 at 01:54 PM |
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Thanks Matt - it looks like in your posts you are referring to the dia of the driveshaft itself (i.e. the bit between the two tripode joints). The
part that I was referring to is the shorter length part that attaches the inner tripode joint to the diff itself - does this also vary in diameter
along with that of the main driveshaft?
Pic to clarify:
 
sierra driveshaft
Thanks,
Tom
[Edited on 15/7/09 by djtom]
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bimbleuk
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| posted on 15/7/09 at 02:39 PM |
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quote:
Originally posted by djtom
Quick question - are there two types of push-in Sierra driveshaft? The measurement that I need refers to the splined section that pushes into the diff
itself.
Yes there are two diameters for the splined end that inserts into the diff. The very early Sierras had the smaller diameter. Sorry I don't have
the measurement of the smaller shaft to verify this. I have a spare 7" diff that uses them but no matching shafts but I'd like to find
some.
One way of telling if you have the early diff is to weigh it as its 4 kgs lighter than the more common 7" diff (17-18kg dry).
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avagolen
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| posted on 16/7/09 at 12:53 PM |
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Hi Tom I am getting in a mess with this replay. If you look at the diff from the rear, you should be able to see both of the castings for the
driveshaft insert castings. If you cannot, it is a 6.5 inch" diff. The castings should be about 0.5" deep.
 
Rescued attachment Diff.jpg
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mcerd1
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| posted on 16/7/09 at 01:08 PM |
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isn't that a 7" diff ? like this one:
6.5" diffs are from the front of the 4x4 sierra / cossies - like this one:
.JPG)
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