Sideloader Ratios

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zinnocoupe
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Sideloader Ratios

Post by zinnocoupe »

I am in a discussion with several fellow parts hoarders. Our topic is 3.25 Open sideloader diffs. This unit came from an e9 csi. I'm not real familiar with e9s but I assume this diff is the same sideloader that comes in e3s, e12s, and early e24s. The question is: Is the 3.25 ratio open SL found in our early e24s?? Is this a fairly common ration to find? I see several references to 3.25 sideloaders if I search though this forum so assume this can't be that rare. Hopefully one of the gurus on here has an answer for me....... Brucey, Bobbo . Bueller? :lol: Thx in advance
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Re: Sideloader Ratios

Post by bpoliakoff »

My understanding is the 3:25 is the ratio used with automatic transmission cars and probably why you don't come across them in LSD
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zinnocoupe
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Re: Sideloader Ratios

Post by zinnocoupe »

Right, that makes sense Bert
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Re: Sideloader Ratios

Post by GRNSHRK »

Dave, my '80 came stock with a 3.45 ratio and 4 speed, which has long since been upgraded to a 5 speed OD gearbox.

I have also upgraded to an LSD, it was "supposed" to be a 3.64, which I really wanted, but the "40" stamped in the case was not for the ratio, it's for the % of lockup, 40%.

So yeah, while I do have that, I would still love to go to 3.64, apparently quite rare...

Sounds good on the 3.25 being used with slushboxes, but I really have no idea.

HTH!
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Re: Sideloader Ratios

Post by zinnocoupe »

Bobbo, Thx for the reply. Where is this "40" stamped on the case? I've never heard of this before I thought it was just stamped for example:
11 40 . Meaning 40 Divided by 11 = 3.6363 . or 3.64 . I've not heard of the % of lockup being stamped on the outside of case. I also thought the standard lock up was 25%. Interesting . :-k

heres a diff pic . This one is 13 40 . =3.07 . No "S" . so its open

ImageIMG_7204 by Dave Grayson, on Flickr
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Re: Sideloader Ratios

Post by bpoliakoff »

+1
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Re: Sideloader Ratios

Post by GRNSHRK »

Uh, plus nothin' Bert :-({|=

So, attached photo shows both the all important "S" and "40" stamped next to it =D>

The seller swore that it was a 3.64, 40:11 as Dave duly noted :-"

What I don't have is a photo of the 38:11, which I guess is stamped on the casing somewhere :-k

The seller also told me that the diff was from an older chassis, E3 perhaps, although unlikely, thinking more E9 :-?

And the rebuilder told me that it was one of the diffs that you (or he) could set to whatever lockup ratio I wanted :shock:

I thought that 40% was just fine \:D/
Attachments
3.64 diff2 - S 40.JPG
3.64 diff2 - S 40.JPG (1.01 MiB) Viewed 8878 times
3.64 diff5 - S 40.JPG
3.64 diff5 - S 40.JPG (842.13 KiB) Viewed 8878 times
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Re: Sideloader Ratios

Post by bpoliakoff »

Maybe you have just have opened up a whole new can of worms. Never heard of this option from the factory nor anything more than a 25% lockup It would be neat if you could find some support info. If you can't find any back up, a call to Metric Mechanic may be the only accurate answer
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Re: Sideloader Ratios

Post by zinnocoupe »

Its very interesting and unusual from what I've seen Bobbo. I have an LSD with the S stamped but it still has all the other numbers denoting ratio.

Thats the only spot I've seen stampings so I wouldn't know where else to look.
I wonder, have you confirmed the actually ration by turning the input shaft and counting the number of times the the output shaft turns?

I have heard of a 40% lock up ratio being an option and I "think" I've seen a few cars on the forums that have it but not sure.

As for changing the lock up ratio, I believe thats done by anding more discs into the stack inside the unit. So any diffs ratios can be changed although it requires taking the unit apart obviously. At least this is the procedure for the medium case diffs in later e28 e30 cars.

I'd be interested to learn more about that diff you have Bobbo,

My 3.64 LSD supposedly came from a 50K mile e3, I'll be putting that in my e12
ImageIMG_7223 by Dave Grayson, on Flickr
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Re: Sideloader Ratios

Post by GRNSHRK »

Well, now isn't this getting interesting =D>

So, maybe E3 it is :-k

Curious what that additional "3" is stamped on yours :-?

Shit, think I'd drive all the way to BC to get my grubby fingers on that one :-"

Frankly, while a call to Metric Mechanic might solve this puzzle, I've tried calling them before on other occasions, trying to figure out what coolant hoses I would need for their max cooling package, only to hear crickets :-({|=

Anyhoo, let's keep this one going, getting interesting 8)

BTW, drop me an email when you get a chance, not sure if I told you, but I'm retired now, so the Thermo E addy won't work #-o

[email protected]
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Re: Sideloader Ratios

Post by bpoliakoff »

3:64 is the holy grail for an OD transmission.The E24 guys on the "other" forum and big players on the other coast swear that is the one to get. I myself have seen very, very few 3:64 lsd side loaders. Of course once you have an LSD then it's just a hunt for a diff with the gears and an open diff really doesn't hold much value so that could be a way to go and just build 1 out of 2
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Re: Sideloader Ratios

Post by zinnocoupe »

Yeah I figured there would be a little excitement at the pic of that diff. That came up on CL in Seattle a few years ago. Lucky for me I was the first one to contact the seller and had to go speeding down there from Vancouver the next day. The seller was a Volvo guy and didn't really know what he had until he had 30 or more emails all wanting the diff. Happily he didn't try to jack up the price or anything on me. Its the crown jewel in my parts hoard. As for the other numbers stamped I have no Idea. Every sideloader I see seems to have other random numbers stamped in those locations. Bobbo, yours is the only one I've seen with numbers like that.
I did know you were retired, but forgot. I emailed you a while ago and didn't hear back. So I posted my question here.

Bert, I didn't know that. So you could take an open 3.64 and an LSD 3.46 and make a 3.64 LSD??? Interesting idea. This never occurred to me.
I've got a 3.64 open I just acquired.

Still hoping to find more info about the rarity or not of the 3,25 open diff? Anyone?
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Re: Sideloader Ratios

Post by bpoliakoff »

I think the only difference may be if there is a different bolt pattern on the ring gear. I am not sure if it is the side plate or the ring gear but there is a difference where one uses 8 bolts and the other 10. So if in the ring gears it's a problem. And yes there should never be a problem switching gears from one carrier to the next in the same housing as long as the bolt pattern is the same. I do not believe a 3:25 is rare. IIRC Bobbo had one laying around in his garage many years ago thaat I think he was willing to give away
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Re: Sideloader Ratios

Post by duracel79 »

bpoliakoff wrote: Thu Sep 26, 2019 8:38 pm I think the only difference may be if there is a different bolt pattern on the ring gear. I am not sure if it is the side plate or the ring gear but there is a difference where one uses 8 bolts and the other 10. So if in the ring gears it's a problem. And yes there should never be a problem switching gears from one carrier to the next in the same housing as long as the bolt pattern is the same. I do not believe a 3:25 is rare. IIRC Bobbo had one laying around in his garage many years ago thaat I think he was willing to give away
I have bought and part swapped a few Side loaders for my E21 race car and 8/10 bolt is with respect to the ring gear.
I have heard of the LSD housing being re-drilled to suit the other bolt pattern but can't remember which way round they went.

Externally early side loaders have the flanges retained by a long bolt and the later diffs have snap in flanges. The LSD unit or std Diff carrier are different for early and late and the flanges need to match the diff centre.

The E12 has been the source for me for 3.64, 3.91 & 4.44 ratio open diffs.
We also have a couple of 3.25 diffs one std in our E9 csi and the other from a csl.

Cars which have side loaders with available ratios I have found on RealOEM:

E3 - 3.45 (38:11), 3.64 (40:11)
E9 - 3.25 (39:12), 3.45 (38:11), 3.64 (40:11)
E12 - 3.07 (40:13), 3.45 (38:11), 3.64 (40:11), 3.91 (43:11), 4.10 (41:10), 4.27 (47:11), 4.44 (40:9)
E24(E12) - 3.07 (40:13), 3.25 (39:12), 3.45 (38:11)

Yes the LSD units can be built similar to later units with extra plates, with or without preload.

HTH

Ben
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Re: Sideloader Ratios

Post by zinnocoupe »

Ben, Its very interesting. Thx for posting your info. I don't think I've seen so much info all put down in one spot on diffs before. Many thx

And I just want to clarify
Yes the LSD units can be built similar to later units with extra plates, with or without preload.
By this statement you mean, by adding extra plates you would increase the % of lockup? In other words 3 plates = 25% add a plate= 30% lockup?

And what is the preload?
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Re: Sideloader Ratios

Post by duracel79 »

Yes more plates gives more lockup, but I don't know the actual %'s.

Preload is the force required to turn one output flange independently from the other without any input load.

BMW supplied lsd's have a preload in the region of 50 to 100 ftlb. This is what you measure to see if a std LSD is worn or not.

my race diff now has 6 drive plates (3 either side) and very little preload, which means that at zero input power the diff will act almost like an open diff. However as soon as there is either acceleration or deceleration force then it will start to lock up.

HTH

Ben
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Re: Sideloader Ratios

Post by zinnocoupe »

Ok thx for the info Ben. Thx for replying
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