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26 spline/IRS diff options

244tiCanuck

244tiCanuck

Well-known member
Joined
Sep 3, 2004
Location
Edmonton
Since BNE and Bakaxel no longer seem to offer the 27 spline stub shafts for IRS diffs (not available from either in years), does anyone know of another option for us IRS folks to get a decent LSD going?
I see that Tenaci has a 26 spline torsen style diff, but it's looking like about $2k CAD by the time I get one here and I'd like to get a clutch type diff if I can. I have a G80 3.15 diff from a 960 that I'll run in the meantime, but I'm not so much a fan of G80s for actual fun driving at speed.

I DO have a BMW diff in the right gear ratio with a clutch type LSD, but I sort of consider that the nuclear option, being that it's probably a solid few days of messing around modding the sub frame and then having to get a different driveshaft again.

Is there another way?
 
My math was off. The Tenaci 26 spline IRS torsen would be about $1200 CAD landed (forgot to subtract VAT from item and shipping). That's not bad and I might just go with that and see if it blows up.
 
I *think* you can buy the side gears from Tenaci or Bakaxel and convert a 588 truetrac yourself. Might save some money overall.
 
I read somewhere (here? instagram? a facebook page?) that the 27 spline BMW medium case, large flange drive flanges (of which I have a few) will fit a Volvo dana 30 27 spline diff in an IRS housing, if you modify them for the seal or snap ring or something? I don't have a Volvo 27 spline carrier sitting around to try, but does anyone know if there's any validity to this? The diameter and spline count are the same, from what I can tell.
 
I'd swear some crazy guy in the Netherlands, (who had installed a V12 engine with 12 throttle bodies) also had upgraded the IRS to withstand the expected power of the V12. Can't recall his name/handle.... have not seen an update in a LONG time.

Another Canadian brother of yours might have also started down this path. I think he goes by 940 16 Valve (or similar), and was up in your neck of the Canuckistan woods. I'm sure he had pics of a BMW unit he had harvested and was in process of trying to fit. I believe he went 20 Valve WB in that same car.
 
DET17 said:
I'd swear some crazy guy in the Netherlands, (who had installed a V12 engine with 12 throttle bodies) also had upgraded the IRS to withstand the expected power of the V12. Can't recall his name/handle.... have not seen an update in a LONG time.
Click to expand...
Sander

Thread 'Sander's 6.0 V12 745 project'

I got far enough along now with it to make a new thread. Old thread (16V Turbo) here: http://forums.turbobricks.com/showthread.php?t=165886&page=23

Short recap, I got the car in 2008 with the purpose of putting a V12 engine in it, but due to lack of working space or even a garage I decided to turbocharge it. It's a 745 GLT so it had a 16V engine already. After years the itch to put a V12 in there was still there and now I have a garage and enough space to do it. Then this showed up:

...
 
I saw they were using BMW diffs. I have collected the things to swap to a BMW diff.
What I'm asking, is about modifying the BMW drive flanges to fit a 27 spline Dana 30 carrier, so as to fit an LSD to the IRS Volvo diff and keep the Volvo diff in the car. I think it was a Facebook post or Instagram or something where I saw someone explain that they modified BMW diff output flanges to fit the Volvo diff. The BMW flanges have 27 splines and are the same spline diameter as a 27 spline Dana 30, so it doesn't seem that crazy to me. I just don't have a 27 spline Volvo carrier to try it with and would like some confirmation before ordering anything.
 
So I've confirmed that a BMW 27 spline stub axle fits nicely in a 27 spline Dana 30.
The Volvo CV axles bolt up to the BMW flange.
This will open up options for LSDs without me having to hack up my subframe to swap to a BMW diff and get a new driveshaft and stuff.
I ordered a 27 spline lunchbox locker off Amazon, test fit the BMW axle stub and sent it back hahaha.
Now I'll modify the BMW stub axle to fit the Volvo IRS diff housing side seal and an inner retainer ring.
My mini lathe chuck has no good way to grab it by a machined surface, so I had to make a temporary lathe center to turn the seal surface between centers. It works.
I am considering having it induction hardened for the seal to have a hard surface if that is more cost effective than just shaving it down a bit more and jamming a speedi sleeve on it. There are a few places that do that type of heat treating locally, I have no idea what it costs to run just a couple of parts.
Anyone have any idea what alloy something like this is?
Pics here in whatever order they come out in.



 
I mean, Tenaci sells both a torsion and clutch type limited slip for 26 spline applications as well.
 
244tiCanuck said:
My math was off. The Tenaci 26 spline IRS torsen would be about $1200 CAD landed (forgot to subtract VAT from item and shipping). That's not bad and I might just go with that and see if it blows up.
Click to expand...
What was the best place you found to order the tenaci diff? Also on classic swede it looks like quafe is making a 26 spline diff soon
 
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