Mack Posted January 29, 2006 Share Posted January 29, 2006 o.k. so I was fiddling around in my head with a long list of parts and what will swap and what wont and I came up with this.... taking a J30 VLSD, gutting the carrier out of it, and putting it in an M30 long nose housing. then, using the J30 input shafts and making a hybridized CV shaft utilizing the M30 shafts and putting the M30 rear control arms on my 280ZX (exact same design, just better brakes and the ability to run positive offset rims) now I kn ow a VLSD is not nearly as good as a clutch type or a torsen, but this could be done with very readily available U-Pull-It parts, probably all for under $100, at least at the places where I buy parts. I know some of the guys, and they usually cut me deals, and Im sick of trying to track down the 300ZXT CLSD for the past few years, only to find ones in the $500 price range. when, for only a few more hundred dollars, I could just get a new one. comments? ideas? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 29, 2006 Share Posted January 29, 2006 You can get a new CLSD carrier from http://www.differentials.com or http://www.reiderracing.com for about $500. Quote Link to comment Share on other sites More sharing options...
Mack Posted January 30, 2006 Author Share Posted January 30, 2006 that Im still going to go with this plan. this will not be an everyday track car, just the occasional autocross and spirited bit of driving. may make a rudimentary diff cooler while Im at it tho..... heat is what kills (and makes them work!) viscous LSD's. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 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.... Quote Link to comment Share on other sites More sharing options...
Mack Posted January 30, 2006 Author Share Posted January 30, 2006 although I feel bad because the set-up I have in mind is not nearly as involved. basically, i was thinking of attaching (weld?) some heat sink fins (a lot) to the bottom of the diff and build an airscoop about an inch off the bootom of the diff, but make it wider. maybe put a door on it so I can shut it on long road trips, kind of like the series 1 doors on the aircleaners. it would operate kind of like a diffuser, where it would grab air off the bottom of the car and maybe I could work out a way to spit it out somewhere useful. although, the 280ZX does nothave NEAR the aerodynamic problems as the 1st gens. This will not be a road race car, just the occasional jaunt around the autocross track, maybe se some extended amounts of race time at MSA! I dont need to keep it super cool, just something to help dissapate some of the heat that builds up. maybe put a small fan under there for inbetween runs. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2006 Share Posted January 30, 2006 Your diff won't get hot enough at autox to justify the expense of a diff cooler. If you have a 280ZX you might consider just getting the 300ZX turbo diff cover. I think it bolts right on to the ZX (the Z has some clearance issues) it's aluminum and finned which should have better heat transfer properties, and it about doubles the sump capacity. It also has some areas on the side that are cast for a cooler inlet and outlet, but they don't drill and tap the cover on the 300 ZXT. Easy enough to drill and tap the holes if you still felt like you needed an external cooler. It returns the oil straight to the sump, not to the gears. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 you will find that the mass of the hot differential is soo great that you cannot hope to get enough suface area properly cool the differential with external fins..... The finned rear cover is made of aluminum..in full contact with the gear oil...and was STILL only suitable for "street" use... The pump/cooler will take up heat from the entire housing front to rear and dissipate it quickly through the HUGE surface area of the cooler... The pump/cooler also negates the need for the oversized finned cover... which makes installation much easier.. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 The Nissan finned cover would make the mistake of picking up AND returning fluid to the same area in the differential housing..... The top channel return port would allow fluid to come in contact with the full length of the differential housing before returning it to the pump.... It is important to actually USE the pump and cooler to draw heat from the ENTIRE housing...not just a little puddle in the rear. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2006 Share Posted January 30, 2006 Hmm. All this time I thought oil coolers were intended to cool the oil and only indirectly affect the housing temperature. Seems to me a water jacket and coolant sytem would be a better way to cool the housing... maybe you ought to get to work on that. I used the stock 280Z cover with my LSD and did as many as 12 1/2 hours sessions in one day with 3 drivers and never had any problems with my diff or LSD not functioning correctly. Now that I shimmed mine up I added the finned cover and I'm hoping that the increased sump capacity and the little bit of cooling that the finned cover provides will be sufficient. Hopefully you'll have your water cooled diff sorted by the time I have a failure in the case that I'm wrong. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 ""I thought oil coolers were intended to cool the oil and only indirectly affect the housing temperature"".. ^^^WOW!... I am again...stunned...^^^ You seem to understand some of the finer points...as you mention a waterjacket system...which does a very good job in most cases of getting rid of heat... But you seem to miss the fact that many things in life are half @$$ approximations of what SHOULD be done... Just because Nissan..or Hitachi.. chose to do things HALF @$$ does not mean that We cannot..or should not do them right ourselves... As we have found many times... The systems we have seen employed either by the factory...or by early race teams.. were often NOT WELL THOUGHT OUT... they made provisions for price and ease of assembly... not always because they determined them to be the text book right way to do it... If you were to bother with the trouble of modifying the rear end in any way... why not do it right... By the time you welded fins.. or changed the chassis to accomodate the rear cover... You could have installed all of the fittings for a proper oil cooler set up... You would still be in for a few hundred $$$ for the pump, cooler, and lines... but if you would consider getting a finned rear cover...modifying the chassis to fit.. and buying some sort of pump and oil cooler IN THE FIRST PLACE.. then why on earth would you go and do it WRONG???... did you not even consider that the 2 fittings on the finned rear cover were only intended to be used as PICKUPS...drilling only one side..... And what you took for a return was actually done the way I described with another fitting on the top front area of the housing...???? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2006 Share Posted January 30, 2006 Waste of time/money. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2006 Share Posted January 30, 2006 To directly answer your question of why I did what I did, I did it as part of another project. I wanted adjustable toe and figured while am at it I might as well add the finned sump: http://forums.hybridz.org/showthread.php?t=89111 Cost: $8. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 Wow... I want my stuff to last... Nissan did not build it's consumer cars to stand up to the rigors of racing... they were unconcerned with longevity in competition... likewise... the teams who raced the early Z cars had bugets that were BOTTOMLESS when compared to our meager cash stashes our wives don't know about...they determined that their rear ends lasted LONG enough... they were disposable compared to the lifespan I would like to see from my race cars. I am also pushing the drivetrain of MY race prepped S-30 WAYYYYYYY PAST it's design limits...... with a small block Chevy engine with almost 3 times the power... Driving style also has a lot to do with heat generated in the drivetrain... I would like to use more engine braking without worrying about building up extra heat... Early Datsun race drivers had far less traction from their tires... braking and drivline heat simply could not be generated at the rates that our modern tires will produce.. For all the spit polishing, chrome plating, and powdercoating I see on Z car drivelines... some of these folks could use a little help on spending their time where it counts... You jmortenson may have determined your rear ends to be sufficient..and/or cheap enough to replace regularly... I on the other hand can do the job correctly and have nice stuff for years to come... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2006 Share Posted January 30, 2006 Yep, that's right. Cheap and it's only lasted through 6 years of autoxing at least monthly and a whole bunch of track days. You'll see very quickly that downshifting is an essential part of slowing a Z down on a track, so I always do that. As for tires... well I'm running 250/45/15 Yokohama A005 slicks so I think I could say that I can and have generated some heat back there, although I did start with street tires then move to DOTs, so it only really had 4 YEARS of the slicks. I suggest you spend your money where it's needed. But it's your $$$. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 I am posting here to provide ideas and information to a forum that has much useful information... not all of it right... When I see someone posting information on systems that they may have seen in use first hand...but are still WRONG... I will let them know about it... I was as tactful as I could be in describing the operation of the system in GREAT DETAIL... and then you post this.. ""It also has some areas on the side that are cast for a cooler inlet and outlet, but they don't drill and tap the cover on the 300 ZXT. Easy enough to drill and tap the holes if you still felt like you needed an external cooler. It returns the oil straight to the sump, not to the gears."" I'll quote myself: ""did you not even consider that the 2 fittings on the finned rear cover were only intended to be used as PICKUPS...drilling only one side..... And what you took for a return was actually done the way I described with another fitting on the top front area of the housing...????"" all of this AFTER I have described the proper way to set up a cooler in a differential of this type...and a description of a historic attempt at a similar system. None of the finer points have been adressed... like maximum fluid temperature acheived without an oil cooler???... or where to place the thermo switch???... brands of pumps available???...what kind of coolers???? proper hose types??? proper fluid types and their acceptable operating temps... clearance and mounting locations???? Just someone getting into a *&$$ match over old misnomers... let's move beyond this to more important matters. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2006 Share Posted January 30, 2006 OK, let's take a step back. Mack says this is going to be a street/autox car. Do you think your super-wazoo cooler is necessary for street/autox car? I stated my own years of experience, but I actually have quite a bit more than my own experience to fall back on. My friends with 510s have been using Nissan LSD's for longer than I have. None has an oil cooler. All run DOT's or slicks. All have MUCH more track experience than I do, as well as close to a decade more autox experience. Not one has had a diff failure that I'm aware of, but I've only been privy to their parts failures for the last 15 years or so, so admittedly there might have been something in the late 80s that happened that I'm not aware of. I haven't seen it in a long time, but I am pretty darn sure that the Nissan Comp catalog from about 10 years ago had a picture of the diff cooler system, and that it sucked out of the lower port in the cover and returned to the higher port in the housing. I'm 99.9999% sure. You can drill a hole in the housing and add a fitting or whatever you want to do on your car. Please post a thread with your results when you're done. But that's not the way the Nissan Comp oil cooler worked IIRC. Cooler fluid in the sump gets recirculated through the diff by the ring gear. That was the idea. The oil is a coolant as well as a lubricant. You're right about that. I guess the question is how much heat is too much, and how much expense is justified in trying to "fix" this "problem". That's where we disagree. Unfortunately, as is your MO, you seem to be intent on calling anyone who disagrees with you patently wrong. That's the part I take issue with. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 Jon.... I made no derrogatory remarks about you or about your opinions.... I made a factual statement "The Nissan finned cover would make the mistake of picking up AND returning fluid to the same area in the differential housing....."" Your response was a dismissal and derogatory in tone by alluding that I should go and make my super water cooled jacket which was never part of the discussion..but a crappy diversionary load of BS... this post also shows your ignorance..which I am in a mood to point out.. Jons quote>> "Hmm. All this time I thought oil coolers were intended to cool the oil and only indirectly affect the housing temperature. Seems to me a water jacket and coolant sytem would be a better way to cool the housing... maybe you ought to get to work on that." Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2006 Share Posted January 30, 2006 You're right. I made the first openly sarcastic comment. Sorry. Still a waste of money on a street/autox car like Mack's. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 30, 2006 Share Posted January 30, 2006 so you let me school you and showed your butt... to simply say that you have never messed with an oil cooler.....and you dont see why... and you seem to know of no one who even runs a high powered engine on an old school car... and your "catalog picture" of the oil cooler set up was G@& &@^^ MOCK UP!!! for a picture in a catalog...!!!! I have a few old school nismo catalogs... the only oil cooler photo I can find is for a solid axle..and it also includes slingers and traps to further control oil flow in an awkward flow....live axle application...without the cover in place...which would seem to show the importance OF FLOW in the system...VERY different from your perception... Quote Link to comment Share on other sites More sharing options...
5foot2 Posted January 31, 2006 Share Posted January 31, 2006 So.... what about the short nose vlsd in the long nose case? Anyone looked at it, done it, knows a friend who knows a guy who's fathers brother did it? Quote Link to comment Share on other sites More sharing options...
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