Welded Diff for Rally?

But seems so easy to remove 2 mm of material from cover, the 2mm spacer and have four clutch plates instead of two.
Notice the washers are available in 1.8 to 2.3 mm and plates in 1.9 - 2.1 mm thickness. Only one belleville. How do you decide how tight the belleville ends up at?

05 33141201939
Stop disk. 1,80MM

05 33141201938
Stop disk. 1,85MM

05 33141201937
Stop disk. 1,90MM

05 33141201936
Stop disk. 1,95MM

05 33141201935
Stop disk. 2,00MM

05 33141201934
Stop disk. 2,05MM

05 33141201933
Stop disk. 2,10MM

05 33141201932
Stop disk. 2,15MM

05 33141201931
Stop disk. 2,20MM

05 33141203791
Stop disk. 2,25MM

05 33141203792
Stop disk. 2,30MM

06 33141206919
Stop disk

07 33141204367
DIAPHRAGM SPRING

08 33141203795
OUTER DISC. 1,90MM

08 33141203796
OUTER DISC. 2,00MM

08 33141203797
OUTER DISC. 2,10MM

09 33141210626
INNER DISC

10 33141206909
COMPRESSION RING

---

Grant Hughes

#7 is belleville spring---one on each end...at least on ever OTHER ZF , Salisbury, everything else I have been inside of..

Do what you want, you will anyway...But if you understand what you're doing, you need to add a disc #9 and a plate #8 per side....4mm per side so 4 from the cover. 4mm deep in the case.
More surface area just means ALL the clutches and discs last longer... not that they lock up more..

The angle of the pressure rings (what ZF calls them) #10 is what sets the max loading...

But do what you want, I'm sure you set lots of different ZF diffs up and have more info than the 2-03 publications I have from ZF and only dome 5-6 ZF diffs--and bunches of others.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham
#7 is belleville spring---one on each end...at least on ever OTHER ZF , Salisbury, everything else I have been inside of..

Do what you want, you will anyway...But if you understand what you're doing, you need to add a disc #9 and a plate #8 per side....4mm per side so 4 from the cover. 4mm deep in the case.
More surface area just means ALL the clutches and discs last longer... not that they lock up more..

The angle of the pressure rings (what ZF calls them) #10 is what sets the max loading...

But do what you want, I'm sure you set lots of different ZF diffs up and have more info than the 2-03 publications I have from ZF and only dome 5-6 ZF diffs--and bunches of others.

Hey John, what I meant was only one option for the belleville, not sure if you need more than one option. I thought you'd once said shimming OR going to a thicker belleville changes characteristics of the diff.

I will do what I want, hopefully with help and input from you.
So what does adjusting the thickness of the clutch plates or the shims do to the characteristics of the diff?
What do you think is a good ramp angle for RWD? We've modified Subaru ones but maybe want a little different for RWD I would think.
Send me copies of those ZF publications.

---

Grant Hughes

Quote
NoCoast

Quote
john vanlandingham
#7 is belleville spring---one on each end...at least on ever OTHER ZF , Salisbury, everything else I have been inside of..

Do what you want, you will anyway...But if you understand what you're doing, you need to add a disc #9 and a plate #8 per side....4mm per side so 4 from the cover. 4mm deep in the case.
More surface area just means ALL the clutches and discs last longer... not that they lock up more..

The angle of the pressure rings (what ZF calls them) #10 is what sets the max loading...

But do what you want, I'm sure you set lots of different ZF diffs up and have more info than the 2-03 publications I have from ZF and only dome 5-6 ZF diffs--and bunches of others.

Hey John, what I meant was only one option for the belleville, not sure if you need more than one option. I thought you'd once said shimming OR going to a thicker belleville changes characteristics of the diff.

I will do what I want, hopefully with help and input from you.
So what does adjusting the thickness of the clutch plates or the shims do to the characteristics of the diff?
What do you think is a good ramp angle for RWD? We've modified Subaru ones but maybe want a little different for RWD I would think.
Send me copies of those ZF publications.

Its all pre-load. Everybody makes one bellville spring, and some you add thicker plates--check the price..some you add thicker shim, some like these ZF things a thicker washer.
Pre-load;
sometimes last century I axed reigning Swedish Champion Ola Strömberg what 'everbody' set preload or break-away at for FWD cars--since that what he drove and I was driving too..
He said and I quadruple checked it about 175 ft/lbs "so you can limp out" . I said the sswedish equivalent of "Shit the bed!!!! 175 break away?" What then do RWDs go for?
He said around 220-240 ft/lbs and then he 'splained the way you check and set...
(For those that haven't done this its simple: get 2 spare output flangies and splined studs, weld a big 1"-1'1/4 nut on each, put one in a vise and put a wind up torque wrench on the other and pull.
Say you set the torque wrench to 175.. If the torque wrench clicks before the diff turns, you're over 175... conversely if the diff rotates before the wrench clicks off, you're under... dismount diff, whip it apart and add or subtract a 0,25mm or .010" shim, reassemble and check again..Usually takes 4-5 times to get it close.)

.010" changes things...

Ramp angles: I can't say what ideal is. Most old non-Ford designs are 90 degree included angle or 45 degree pressure angle...Ford had ZF make em 30 degree PA or 60 included...worked more aggressively or something.. Now there so many choices.. I do know that the variety of angles on drive and kinda open on coast was driven by need fro better turn in on FWD cars on asphalt with crazy tarmac tires...we don't do tarmac with crazy 200 hp fwd cars so maybe not so much issuse..

Besides, the surface of the pressure rings are hardened probably .015-.020" so if we were clever and re-machined the angles, what are we gonna do about the heat treat? Re-heat treat? I can do that for cheap cash only deals but is it worth it for a potentially piddly difference?
I dun't zink so.

So just shim the thing, and get it installed.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Here's stock BMW ramp angles, 45 on both. I'll likely leave them as is for now as I liked the welded diff once I got use to it so am not really afraid of big lockup under decel.

Regarding heat treating, as far as I know the modified diff that had ground ramp angles on the Salta STI that Dick Rockrohr still rallies has held up to way more torque on a way smaller diff without any post grinding heat treatment. It's like the T5 input shaft ground down to fit 2.3 pilot bearing. Sure, the heat treatment is gone, but does it really matter in a rally car application?

---

Grant Hughes

So that's set up for the same lock up in drive and coast. 45deg does seem a little soft though, especially with only 2 friction plates.... I like John's suggestion of adding another set in there.

A part that small is going to have really good through hardness on heat treat. If it's Nitrided, then you could have some issues. Nitriding only effects the first 0.5mm or so. Stupid little Nitrogen interstitials....

But yeah. If the section isn't black (a very good indicator of Nitriding), then you should be find to grind away if you desire.

Okay John, I disassembled and measured internals today.
The inner spacer/shim is 4 mm thick, 89.35 mm out diameter (maybe 90 mm if caliper is out of spec), 49.35mm inner diameter.
Clutch disc is 2.0 mm

Stop shims are 1.9 mm
Stop disc are 2.2 mm

My first thought was get the 2.3 mm stop disc and 2.1 mm clutch disc and check it from there, adding more shims to get more preload.
Got a good source for discs and shims? Or recommendation on where to buy other than going down to a dealer that likely doesn't sell the shit anyhow.

I realized the diff I thought was seized is actually a 3.15 LSD out of the donor car I bought for the engine and it just is a bit tough to spin by stub shafts. I'm going to go ahead and swap that in to run the hill climb in two weeks, seeing as we have plenty of other work to do in the one shop day and two shop nights between now and then.

---

Grant Hughes

What about using a e36 BMW LSD with a 3.91 ratio? They supposedly have the same bolt pattern on the half shafts as the XR's do.

Quote
cmanreinhart
What about using a e36 BMW LSD with a 3.91 ratio? They supposedly have the same bolt pattern on the half shafts as the XR's do.

They do...but they use M10 bolts.. And 3.9 with the ridiculous 1st in the BMW box would make 1st utterly useless, but not short enough to want to get a good drive starting in 2nd..

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham
They do...but they use M10 bolts.. And 3.9 with the ridiculous 1st in the BMW box would make 1st utterly useless, but not short enough to want to get a good drive starting in 2nd..

Hmmmm interesting, If I could drill out the XR's half shafts that might be a swap worthwhile...

Quote
cmanreinhart

Quote
john vanlandingham
They do...but they use M10 bolts.. And 3.9 with the ridiculous 1st in the BMW box would make 1st utterly useless, but not short enough to want to get a good drive starting in 2nd..

Hmmmm interesting, If I could drill out the XR's half shafts that might be a swap worthwhile...

What? The Bowel Movement Wonder diff ?

No they are weak and bust the half shafts easily,,Besides you have to fab mounts and Beemers never make 2 rear diff covers the same , and they are too narrow and who wants a wimpy 3,9 7" diff with a limp-wristed 3,9 ratio when you could have a strong 4,3 ratio, 8 inch ring gear, easy to adapr diff that alternate ratios cost 139 to 190 bucks for new ring and pinion sets vs the Bring More Wampum's ONE MILLION DOLLARS for any ratio..
Why?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham
What? The Bowel Movement Wonder diff ?

No they are weak and bust the half shafts easily,,Besides you have to fab mounts and Beemers never make 2 rear diff covers the same , and they are too narrow and who wants a wimpy 3,9 7" diff with a limp-wristed 3,9 ratio when you could have a strong 4,3 ratio, 8 inch ring gear, easy to adapr diff that alternate ratios cost 139 to 190 bucks for new ring and pinion sets vs the Bring More Wampum's ONE MILLION DOLLARS for any ratio..
Why?

^ This!

Matt's had nothing but trouble with the BMW stuff, though he may be a bit harder on equipment than most. On my BMW compact I went the supra route and while that was a gigantic pain (fab work), the diffs are cheap, the rebuild kits are cheap, and ring & pinions are cheap and ratios plentiful.

Dave

Quote
cmanreinhart
Hmmmm interesting, If I could drill out the XR's half shafts that might be a swap worthwhile...

Sean Medcroft did a BMW E36 diff into his Merkur. Okay for convenience purposes but the Supra is an easier and probably cheaper option.

Quote
JVAB
Besides you have to fab mounts and Beemers never make 2 rear diff covers the same and they are too narrow and who wants a wimpy 3,9 7" diff with a limp-wristed 3,9 ratio when you could have a strong 4,3 ratio, 8 inch ring gear, easy to adapr diff that alternate ratios cost 139 to 190 bucks for new ring and pinion sets vs the Bring More Wampum's ONE MILLION DOLLARS for any ratio..

They made three different diffs pretty much forever. The 188 mm ring gear, so called the medium case, which is a 7.4" diff which is not a 7" diff.
They made the medium case with lots of ratios, but the 3.91 is lowest that was sold in an E36 so you might have to get a junkyard or ebay used 4.1 which is really not a super hard and difficult thing to do and they were sold in enough different cars that I found one during BOGO day at the U-pull and an LSD center section. In Europe they also made a 4.27 which can be found on ebay for anywhere from $50-200.
The Supra diffs are great and should be main choice for something like a Merkur, but the BMW ones are total garbage, uber-expensive (unless you choose to make it that way) nor are they totally impossible to make into a decent rally diff.

---

Grant Hughes

Quote
NoCoast

Quote
cmanreinhart
Hmmmm interesting, If I could drill out the XR's half shafts that might be a swap worthwhile...

Sean Medcroft did a BMW E36 diff into his Merkur. Okay for convenience purposes but the Supra is an easier and probably cheaper option.

Quote
JVAB
Besides you have to fab mounts and Beemers never make 2 rear diff covers the same and they are too narrow and who wants a wimpy 3,9 7" diff with a limp-wristed 3,9 ratio when you could have a strong 4,3 ratio, 8 inch ring gear, easy to adapr diff that alternate ratios cost 139 to 190 bucks for new ring and pinion sets vs the Bring More Wampum's ONE MILLION DOLLARS for any ratio..

They made three different diffs pretty much forever. The 188 mm ring gear, so called the medium case, which is a 7.4" diff which is not a 7" diff.
They made the medium case with lots of ratios, but the 3.91 is lowest that was sold in an E36 so you might have to get a junkyard or ebay used 4.1 which is really not a super hard and difficult thing to do and they were sold in enough different cars that I found one during BOGO day at the U-pull and an LSD center section. In Europe they also made a 4.27 which can be found on ebay for anywhere from $50-200.
The Supra diffs are great and should be main choice for something like a Merkur, but the BMW ones are total garbage, uber-expensive (unless you choose to make it that way) nor are they totally impossible to make into a decent rally diff.

Yeah yeah whatever the actual measure is Grant---and I'll bet a whole nickle that you have not disassemble a Ford Xratty 7.5" and the whatever the fuck the Krauts want to call their "bigger one" and laid the parts side by side...the so called bigger one is "One Full step" smaller ring gear...
Whatever the fuck its called, it is obviously and significantly smaller..

And usually when I try or suggest and upgrade I usually try to upgrade to stronger things than I'm taking out---and I don't let brand loyalty blind me...

The bigger size, unbreakable strength and stupid cheap cost for second hand gears---$12 off ebay for a 4.3 set---should be obvious choice

Second,

Sean did 2 or 3 BMW diff assemblies... and then when people had inner CV over extended because the diff is "that much" narrower, he came to somebody that is a bit more careful and who measures things--- and I made some CV spacers out of some old dead CVs--sliced a 4-5mm section off--..
I have said the ZF and Salisbury type diff I like--its my preferred design...so
BMW easy and for some cheap but for rally use good decent ratios are THOUSANDS of DOLLARS, and they're still small, and driveshaft length is a instant problem requiring attention and cost.

Why bother?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham

Quote
NoCoast

Sean Medcroft did a BMW E36 diff into his Merkur. Okay for convenience purposes but the Supra is an easier and probably cheaper option.

Quote
JVAB
Besides you have to fab mounts and Beemers never make 2 rear diff covers the same and they are too narrow and who wants a wimpy 3,9 7" diff with a limp-wristed 3,9 ratio when you could have a strong 4,3 ratio, 8 inch ring gear, easy to adapr diff that alternate ratios cost 139 to 190 bucks for new ring and pinion sets vs the Bring More Wampum's ONE MILLION DOLLARS for any ratio..

They made three different diffs pretty much forever. The 188 mm ring gear, so called the medium case, which is a 7.4" diff which is not a 7" diff.
They made the medium case with lots of ratios, but the 3.91 is lowest that was sold in an E36 so you might have to get a junkyard or ebay used 4.1 which is really not a super hard and difficult thing to do and they were sold in enough different cars that I found one during BOGO day at the U-pull and an LSD center section. In Europe they also made a 4.27 which can be found on ebay for anywhere from $50-200.
The Supra diffs are great and should be main choice for something like a Merkur, but the BMW ones are total garbage, uber-expensive (unless you choose to make it that way) nor are they totally impossible to make into a decent rally diff.

Yeah yeah whatever the actual measure is Grant---and I'll bet a whole nickle that you have not disassemble a Ford Xratty 7.5" and the whatever the fuck the Krauts want to call their "bigger one" and laid the parts side by side...the so called bigger one is "One Full step" smaller ring gear...
Whatever the fuck its called, it is obviously and significantly smaller..

And usually when I try or suggest and upgrade I usually try to upgrade to stronger things than I'm taking out---and I don't let brand loyalty blind me...

The bigger size, unbreakable strength and stupid cheap cost for second hand gears---$12 off ebay for a 4.3 set---should be obvious choice

Second,

Sean did 2 or 3 BMW diff assemblies... and then when people had inner CV over extended because the diff is "that much" narrower, he came to somebody that is a bit more careful and who measures things--- and I made some CV spacers out of some old dead CVs--sliced a 4-5mm section off--..
I have said the ZF and Salisbury type diff I like--its my preferred design...so
BMW easy and for some cheap but for rally use good decent ratios are THOUSANDS of DOLLARS, and they're still small, and driveshaft length is a instant problem requiring attention and cost.

Why bother?

The reason I was thinking "BMW LSD Diff swap" was because it seemed like the most straight forward swap in terms of having the same blot pattern on the CVs. Also another reason behind going BMW was that for my senior year in High School I need a Senior Project for my Engineering class (I probably sound like a yung noob right now saying this since I'm a 16 year old kid talking on a rally forum). But with that in mind I'd probably end up designing some mounting brackets on SolidWorks then ordering the desired square tubing or whatever and welding them together to mount up the Bimmer diff.

The reason for not going Supra is that I'd have to design and make CV adapters, and right now i just don't feel like I have the skill level/resources to do that.

So at the end I hate to sound like an asshole trying to take business away from John you its just that for my "Senior project" I'd like to design up some cool for my XR (like a diff swap) Instead of something stupid like designing and 3D printing a gay model trail (nothing wrong with model trains, just not my thing).

Anyways maybe id be still interested in doing a Supra Diff swap if some how I could only buy the CV adapters, and then just design up the brackets to mount it....

Hope you guys understand since I've put a lot of thought in this, and how I might go about doing a diff swap for a senior project.

-Thanks, Conner