bjhines

I had an opportunity to speak at length about differential and tranny coolers with a pro BMW race car builder... The rear ends in the BMWs are similar to what Hitachi produced for our Z cars... I tracked down an old plan for a cooler set up used in Z car differentials way back in the 70s...It incorporated a themo switch in the drain plug... a relay and an electric pump... The design used the breather port in the top of the cover as a pickup..extended internally of course...this ran to the pump..through the cooler...and returned via a port drilled into the top of the differential housing... It would appear that the return port squirted cooled fluid directly onto the pinion...I guess the idea was to cool the highest friction area directly... I bounced this design off the BMW expert and he had some surprising responses and ideas... first off.... There is no provision for a breather in the old Datsun race car design...This would be a mistake...any design must incorporate a breather and a catch tank... secondly.... There is no provision for reducing the amount of metal bits in the oil moving though the pump...bad idea...and easily fixed...the reason for using the modified breather port may have been to allow the extension to draw fluid off the top of the pool...thereby avoiding most of the metal bits in the bottom of the housing... there is however a greater risk of cavitation in the system under high G loads.... an easier solution is to use a magnet in a small inline bowl to catch the metal bits without building up and blocking flow(magnetic filter)... Third...and most important... where to return the cooled fluid???...It seems that it is a bad idea to squirt the cooled fluid directly on moving parts...especially the pinion and/or the ring gear...excess oil will be flung off the parts with great force and will cause foaming of the fluid...this will also cause a great deal of parasistic drag...the foamed fluid will expand a great deal and may end up in the catch tank instead of the differential where it is needed... I was told to return fluid to the top front of the differential housing where it can run both fore and aft in the top channel...feeding extra oil to the pinion shaft and the pool in the main part of the housing...oil can run freely through channels cast into the housings in the top and bottom front portions of the housing... The pump and cooler should work with as little back pressure as possible...there should be a kill switch in the car to allow the driver to shut off the pump in case the cooler is damaged... the pump should flow around 5liters per min free flow..this will be much less in operation though the cooler. Also... the pump and cooler should be placed at or below the fluid level in the differential housing.. so that drainback will not overfill the housing and cause leakage during storage... I thought you guys might like these ideas....

absolutely... the bolts are threading into the original buttons that datsun pressed into the side gears on the original R180s that came in 240Zs. The "buttons" fit 25 spline side gears... also the same as used in Subaru R160s and R180s... the only problem I have found witht he Subaru diffs is that the R160 is much narrower than the R180... so the stubshafts will stick out of the sides of the R160 a few mm... but I do not see a problem with this in operation..

you dont need to cut or weld anything for any R180 if you do what I outlined above... the only thing you have to check is the 25 spline shaft.

Haaa... our Z car club president traded his 240Z for a supercharged Hoosier slicks miata.... as I recall I bested his times throughout the last event...although we were close...but the driver is still learning his car... Oddly enough...our track events coordinator owns a 1971 240Z and seems to want to replace it with a BMW E30.... If I were going to compare 2 close performers...I would say that the BMW E-30s are the closest match for a 240Z... Mine is a 1972 240Z with the original L24..rebuilt in 1986...sat in a barn for almost 2 decades... I woke it up with some headwork and a cam and put MSA blue springs on it with blue tokico shocks...replaced all bushings and slotted the strut towers and shaved the upper mounts for added negative camber.. bigger front sway and added a rear sway bar... I run on 225/50/15 Victoracers, or 205/50/15 Azenis.... AND I use stock brakes with track pads.... I would say that a well prepared Z car will beat most well prepared Miatas...at least the Miatas don't do very well at our events... I have video of my 240Z chasing down another track prepped Miata with slicks that stick WAYYYY outside of the wheel wells... I have driven another supercharged Miata on the street and it was FAST!!!... but I wondered at it's capability on the track... The Z car puts down more power with similar mods... with an LSD and some suspension tuning you can get an amazing amount of speed from a Z car...

This may have contributed to the tearing of the internal teeth on the disks in Phixius' LSD.... as the internals wore... the movement of the side gears became excessive... the teeth on the disks were being wrenched in 2 dimensions against a cheese grater quality surface and ripped off the disk... You may gain life in these units by smoothing the notches in the side gears and limiting axial movement with some sort of case to side gear spacer.. even if it only comes into play as the unit wears out...the spacer would need a recessed area in the case.... deep enough as well...

they do indeed look brown on the ends...This clears up much for me...Why on earth did you post that other side gear picture knowing it was new and showed ZERO wear... That does possibly mean that they are supposed to operate without static lash... it is unlikely there is another static contact point... but that does not change the fact that the gears wont take any abuse without static lash... that is a half *** stab at a good unit...I am seriously dissapointed... 4x4 folks have known that for years... I am willing to entertain the idea that this is a FUNDAMENTAL FLAW in the notoriously weak 300ZXT LSD units. I would love to see what the wear rate is on a new set of internals during track use... The stock units could be seriously upgraded with proper spacers with minimal cost.. There must be a reason.... like thin wall thickness.... the units may tend to split under shock loads when you do that... I will measure case dimensions on the NISMO unit as well...

I cant tell what the surface looks like in that picture...blow it up and crop it at a better resolution...and the dam cups are face down.

but the rear faces of your side gears have ZERO wear as well... they are cross radially machined still...

I am not trying to be insulting... I have one I found in a parts pile...and it left me stranded a long way from home...verrry expensive tow...it's internals now serve as weights for gluing up woodworking...It did not have proper axial thrust clearances when I ineptly set it up in a worn out used up 14 bolt quite a while ago... If the side gears are not set up right... there will be exessive slop in the drivetrain...just like a worn out set of spiders and sides..the lsd does not inherently have more slop than the open diffs.... the proper set up of the internals and the sprig plates are there to eliminate this...at least until the springs compress. There is no thrust washer behind the side gear face... as I explained.. those pictures in my album with thrust washers on the back/widest flat rear are for R180 OPEN DIFFS...MY R200 LSD side gears have never come close to touching the inside cup of the pressure disk.... This is the R200 LSD side gear and inside of the cup... http://album.hybridz.org/showphoto.php?photo=5416&size=big&cat=500&page=1 These are the side gears for the R180 open diff.. The left hand side had never turned before.. it was butt spanking brand new...notice the tumbled finish on the left hand spacer...pretty crappy ehh...and I was always sooo careful cleaning them... http://album.hybridz.org/showphoto.php?photo=5395&size=big&cat=500&page=1 it should be more than obvious... that they do not have the notches for the clutches to engage...as I previously posted...

I read it and I explained it from the beginning... YOU are misinterpreting Gordon's site... the SIDE GEARS are not what spreads the pressure disks apart... It is in one of you r first condecending posts... I explained it in greater deatail to you than even Gordon's site mentioned... because I understand how it works in great detail. If your gears are thrusting out of alignment axially...or in any direction... they wont last long under pressure...period... This is a basic engineering fact... I can't help it if you found your rear end in some half stripped parts pile and nursed it back together... I'll bet you have some wear marks on one surface or the other now that you have been using it.....I'll bet you find a lot of metal filings in the carrier now as well... how about posting pics of the worn out spider and side gear faces after it breaks during the next track event.

OK then... post a picture of the INSIDE of one of the CUPS/pressure disk... lets see what kind of polish that suface has... because there is absolutly NO polish from wear on the rear face of the side gears... that was one of the big deal pics you posted... if you saw soo many rear ends.. and/or you actually set up new ones into old housings... you would know that there is NO design using side and spider gears on a single cross/pinion... that would allow for axial movement of the gears... period... there is no diff made using those parts that does.....err....well one... There is only one that I know of.. and it used 2 separate spiders pinions that had the ability to ramp the spiders inward /radially on the face of the side gears... this accounted for the axial displacement of the side gears in the carrier... and this design was for a FULL FLOATER axle style...

The only R200LSD parts are named as such in the album...be careful what you are looking at. The spacers with the oil holes are for the R180 open diffs...you will see that those side gears have no slots for the cluches in the LSD... Which pertains to another post I made about how to convert ANY R160 or R180 from Subaru, late Nissans, etc.... the conversion allows you to BOLT your old 240Z stubs into the NEW snap in style R180s... which is trickier than you might think...there is no easy conversion to allow factory style halfshafts and side flanges..except mine...which seem to be ground breaking. I checked this out today... and the R1XX tend to use the same 25 spline equal length studs... The R190s use a combination of 27 and 29 spline axles...of course the R200s use unequal legth 29 spline SNAP IN stubs...which is easy to convert to S30 chassis. ok... welll... your side gears show no wear on the back side of the gear face either.....you see the machine marks on them.... so dont get any ideas that your gears thrust back and forth axially.... This is one of many LSD units i have set up and installed... The gears thrust clearances are set static... I have never seen a clutch type that was not... This would have been more apparent to you if you had ever seen one in use in a non floating solid rear axle. Here is a picture of the stack on ONE SIDE... http://album.hybridz.org/showphoto.php?photo=5414&size=big&cat=500&page=1 Here is a picture of the ENORMOUS side and spider gears... and the HUGE cross...which by the way allows you to pass a shaft ALL THE WAY THROUGH THE ENTIRE REAR END.... which addresses my question originally. http://album.hybridz.org/showphoto.php?photo=5416&size=big&cat=500&page=1 Here is the LSD case number.... http://album.hybridz.org/showphoto.php?photo=5421&size=big&cat=500&page=1 Here is the ring stamping... as you can see... this is a 39:11 3.54 differential...which should get into the 140MPH mark with the T5 5 speed behind a race prepped 350 V-8. http://album.hybridz.org/showphoto.php?photo=5423&size=big&cat=500&page=1 Soo... all in all.... I am putting this back together soon...seeing how it is a unit that has seen under 2 years of occasional track events with it behind the L28 ... I am sure I will be back into it after a couple of years behind the V-8 T5... If there are ANY dimensions you want... call em out now.... I can get em for you... I will go no further until I hear from you guys.. but make it quick.