AWD and LSD or spools - discuss !
Posted by A1337STI
Pete Remner Senior Moderator Location: Cleveland, Ohio Join Date: 01/11/2006 Age: Midlife Crisis Posts: 2,022 |
Jeff Reamer Mod Moderator Location: Marlette, Michigan Join Date: 08/14/2010 Age: Midlife Crisis Posts: 489 Rally Car: Subaru |
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Except that the drop gear mod wasn't in place of doing diffs it was done in addition to the diffs. (IIRC) First Rally: 2001 Driver (7), Co-Driver (44) Drivers (16) Clerk (10), Official (7), Volunteer (4) Cars Built (1), Engines Built (0) Cages Built (0) Last Updated, January 4, 2015 
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Alex Rademacher Elite Moderator Location: Reno,nv Join Date: 09/10/2007 Age: Midlife Crisis Posts: 686 Rally Car: 93 GC with an 01 RS swap! |
So really all i need is a drop gear and i can forget all my diffs.
how much Tork, sorry Jam do i use when i Titan up the transmission when i'm all done? on a serious note, what does grinding down the ramps do for the Clutch pack LSD Diff? does that make it lock up faster? / more break away torque ? I found a good lead on a cheap (not used in the US) 20 kg center. its phase 1 though. I do have a phase 1 transmision but i found a phase 2 (2002) one with better gears (outback) we may look at moving the gears over to the phase 1 and using 20kg center .. cause i should be able to do it really cheap. Then i'll have 20kg center, and a subaru mechanical LSD rear . i think its a 1-way |
Tony Wells Ultra Moderator Location: Omaha, NE Join Date: 07/08/2008 Age: Possibly Wise Posts: 191 Rally Car: SP Evo IX #112 |
To lock the diff under accel/decel, the pinion stub shaft tries to split the carrier via the ramps and the carrier pushes on the clutch packs. If you look at it from overhead so the clutch packs look like vertical lines and the carrier is split in the middle you can see in your head how it works. Now take the extreme case, a ramp angle of 90*, if you look at it from overhead, that's essentially a "shelf" and pushing on it won't split the carrier. So as you lower the angle, it's going to push on the clutch packs harder. And you can probably figure out that the angles on one side of the shaft are for accel and the on the other side are for decel. If you have a 90* angle on one side, it's a 1-way diff, there's no dynamic lockup in that force direction which usually is decel. I even found a pic of a Ralliart diff where you can see the gear shaft peeking through and the ramp angles: 
All this has nothing to do with breakaway torque. The clutch pack will have some sort of spring arrangement helical or belleville that will pre-load the clutch packs that in part determines breakaway torque. Obviously the friction of the clutch packs matter, you can put shims or more discs to up the breakaway torque, etc.. And as an aside, the salisbury diff is clever as shit. Edited 3 time(s). Last edit at 08/04/2014 01:57PM by Nubby. |
Alex Rademacher Elite Moderator Location: Reno,nv Join Date: 09/10/2007 Age: Midlife Crisis Posts: 686 Rally Car: 93 GC with an 01 RS swap! |
Ah, gotcha. now that is very cool.
so on a 1-way one side would have an angle and the other is gonna be a 90 degree "ramp" but you can grind that into some sorta angle and then its a 2-way? (or perhaps its a 1.5 way if you only added a little bit of ramp) I believe 1 of the 3 clutch pack R160s i have is a 2-way . From the picture and awesome information sharing above i should be able to figure that out very easily if i just take them apart . or take the LSD part out of the carrier ...
I guess the Ideal thing to do would be for me to actually try out both and see if i Like the locking under Decel/braking or not. ... and an other Question (maybe dumb) would a 1-way or a 2-way last longer in-between rebuilds ? I would think the 1-Way would last longer due to paved Transits . every time i'm deceling or braking (maybe to go around a highway off ramp) the 2-way is trying to lock up , and if the paved friction is higher than the break away TQ its not going to be able to, but it will try (thus wearing down) where as the 1-way won't be trying to do anything under Decel/ brake/ coast and should only be wearing out when i'm on the gas, turning, and too much grip forces the lsd to differentiate output speeds . |
John Vanlandingham Super Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Nice piccie. here's looking inside: 
The side gears, planet gears and cross shafts are all nestled in the 2 "Pressure rings". Pressure rings have lugs splining them to the case which you can see in the square form grooves...---and in modern stuff---like last12-14 years you may have shorter "big fawkin teeth----like 4 groups of gigantor splines with a 45* PA which is way better-er-er cause they can be shorter (leaving more area for friction on the discs and plates and for drastically less stress from the 45* thing vs the 90* which makes stresses in the L of the plate..) Like this: SEE drive and coast ramp angles in 120'clock ish position 
So the power flow comes in from ring gear--which is bolted (most of the time except sometime in my Saab) to the diff case and the ring gear goes ----> that moves the case ----> and the cross shaft pushing on the ramps pushes them this way V and that way ^ and that pushes on the clutch discs and plates---which are splined to the side gears into which we have half shafts plugged in.. Changing the angle of the notches---ramps in the pressure rings---changes the rate the cross shaft ride up them and hence rate and max lock up effect... In the beginning there was the 45* pressure angle---makes a 90* angle seen from above... Then in mid 70s Ford came up with 30* PA "pressure angle" for a harder lock and Escort dominated... When the mid 90s came along and much of the rally world did mostly asphalt and people saw how nicely "active" diffs worked (bazzillion dollar clutch plate diffs with elector-hydraulic pressure varying according to what some genius tech nerd decided was needed), and they worked especially well on asphalt, the idea of alternate angles on COAST was introduced so the asphalt guys could get nicer turn in and then progressive lock up on exits.. Interestingly in the years Tommi Mäkinen was being Tomi, Team Manager and ex-Dubya Aresey drive Andrew Cowan of Ralli-Art fame was axed about if they were using active diffs all over 9gotta be some "trick" to 'splain Tomi"s results) and he said "No, clutch plate rear and front" When questioned like "Huh? No active, Oh Noez!!!" he siad "It may not be the most sophisticated set up, but with a clutch plate diff, you know what you have." After all the infinite wisdom generously shared here by people far smarter than Cowan, and far faster than Mäkinen, I look back and can't help wonder how virtually all the world has been fooled into wasting time on Salisbury type diffs when it's been proven right here that lockers are the best set up? 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. Edited 2 time(s). Last edit at 08/04/2014 03:16PM by john vanlandingham. |
Alex Rademacher Elite Moderator Location: Reno,nv Join Date: 09/10/2007 Age: Midlife Crisis Posts: 686 Rally Car: 93 GC with an 01 RS swap! |
That actually does make a heck of a lot of sense now
too bad my R160 trade for a 20KG center fell through.. that would have been perfect and 0$ out of pocket (the best type of upgrade LOL) |
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Banned Super Moderator Location: the end of the universe Join Date: 02/12/2006 Age: Possibly Wise Posts: 1,432 Rally Car: 1980 Opel Ascona B |
You can swap center diff sections back and forth between phase 1 and 2 transmissions, it's a direct bolt up either way. The only thing you have to watch out for is the transfer gear situation. The early center diff section uses 1:1 transfer gears so it's not going to work for an early WRX unless you're using the same R&P ratios fron and rear. A phase 2 gearset will not work in a phase 1 transmission case because they moved the position of the reverse idler gear by 1mm and shit won't mesh. |
Alex Rademacher Elite Moderator Location: Reno,nv Join Date: 09/10/2007 Age: Midlife Crisis Posts: 686 Rally Car: 93 GC with an 01 RS swap! |
wow you just saved me (well mostly my crew chief) a lot of wrenching time .
our phase 2 transmission is a 2002 Outback far as i can tell it does the normal 1:1 transfer gears as both its front and rear FD ratios are 4.11 thanks mr Clarkinen
I'll be getting a slightly longer 1st and 2nd gear , and a much shorter 5th by moving over to the outback transmission. i **think** the gears are slightly wider and there for maybe stronger as well. but it was a free upgrade for me (also gives me a spare transmission) so i jumped @ the chance. |
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