Jump to content
HybridZ

Non-Conventional Differential Options...


Mikelly

Recommended Posts

I'm starting this thread for several reasons, and I'm sticking it, as I hope we get some serious development to come out of it...

 

Two things brought this issue to mind... Tom Barnett (Mayolives) continually breaking CV joints at road courses, and Jody Creegan (JBC3) breaking a forged stub axle.

 

Non-conventional (ie NON-Nissan) differentials/ axles are the topic of discussion, and here's why:

 

The traditional Chapman strut/ diff design is not the most practicle design, and is limited.

 

The gear selections are extremely limiting for those who need TALLER gears for road course duty.

 

The CV Axle/ Half Shaft/ Hub carrier/ stub axle/ Bearing is very limited, and a potential failure point.

 

You can keep or discard the chapman strut housing, doesn't matter to me...

 

So what are the options???

 

Ford 8.8 center? Winters Quick Change? Chevy Corvette C4 differential/ Axles?

 

This discussion will include the removal of the existing Nissan differential, Axles, and modify the strut assembly as required to accomodate something more significant, without giving up the independant rear design... SOLID AXLE DESIGNS need not apply...

 

Come on you engineering gear heads. Weigh in here...

 

Mike

Link to comment
Share on other sites

  • Replies 55
  • Created
  • Last Reply

Top Posters In This Topic

Hi Mike:

 

No answers, but a suggestion...

 

Someone already does an IRS Ford 9 inch for Cobra Replicas. Now I know that it has inboard disk brakes, but that shouldn't be insurmountable - either modify floor pans or do a conversion w/o the inboard disks...

 

My reasoning is simple - the Ford 9 inch is the strongest out there with a wide variety of ratios available - why bother with anything less?

 

Of course, this is JMHO....thrown out for cussin' and discussin'...

Link to comment
Share on other sites

Guest bojo68

Just going to throw out some things to consider-

Super coupe tbird IRS

03-04 Cobra irs

Jaguar IRS(inboard brakes)

750 BMW

Corvette Transaxle

Viper

928 Porsche(tramsaxle)

Old Mercedes 280-300 used a swing axle that technically is IRS, but I would not want to do it.(the 6.3's would gobble them up)

Link to comment
Share on other sites

Hi Mike:

 

No answers, but a suggestion...

 

Someone already does an IRS Ford 9 inch for Cobra Replicas. Now I know that it has inboard disk brakes, but that shouldn't be insurmountable - either modify floor pans or do a conversion w/o the inboard disks...

 

My reasoning is simple - the Ford 9 inch is the strongest out there with a wide variety of ratios available - why bother with anything less?

 

Of course, this is JMHO....thrown out for cussin' and discussin'...

 

that's what i was thinking... like a quick change domestic IRS.

 

i saw a 510 with a jaguar IRS setup.... inboard discs, though

 

EDIT - bojo beat me to it!

Link to comment
Share on other sites

As far as the ford 8.8 IRS - none of the new Hi-Po Mustangs have them. I have heard a lot about breakage with lots of torque...

 

I don't think that a transaxle would be the way to go because our weight distribution is pretty close to 50/50 already (for handling) and a forward weight bias and associated weight transfer can only help when drag racing.

 

I was very aware of Cobra kits that utilized the Jag IRS, but I thought the purpose of this exercise was to provide a WIDE range of gearing, which ain't exactly the case withthe JAG unit.

 

Once again, JMHO's...

Link to comment
Share on other sites

I think for road course duty, Tom has the set up figured out. The stock axels were a little long. This, along with the reversed CV cages which limit the angle the cv's will function with out binding, were causing the CV's to bind. He had shorter axels made and his problem is solved. I believe something around 7/8 inch shorter.

 

 

Having had much experience with the Q45 diff conversion on many years of track events, I can tell you I will not do that set up on the next car. The main reason is weight. A clutch lsd in an r200 and Tom's axels with CV's will handle anything I can give it.

 

 

For the straight line guys, I'll sit back and learn something.:icon46:

Link to comment
Share on other sites

Like MARK said,the R200 is plenty strong for road course duty.Tom's new axles did the trick,but his ride height is still a bit compromised.The diff and whole rear suspension is just in the wrong place for our needs.So...Bain Williams new V8Z will be sporting what we hope is the solution.We're still some months away from completion.Photos will follow upon completion.Sorry to seem to be a bit off topic,but I think this geometry stuff relates to whatever diff is in the Z.

Link to comment
Share on other sites

Once you get CV's installed the location of the diff is much less critical than it is with the U-joints. I wonder if the solution to these issues along with a lower PMOI might be obtained by moving the diff forward. Take a look at a 911 and the transaxle outputs are 2-3 inches ahead of the companion flanges. No reason we shouldn't be doing the same thing.

 

Alternatively there is the Terry Oxandale method of moving the diff up, although this raises the cg.

Link to comment
Share on other sites

Usually tall gears and road courses aren't compatible. Have you tried to figure out exactly what gear ratio you'll be needing? What is your redline rpm, what trans are you running, what tire size in the rear, and what do you figure your top speed will be? This might help you figure it all out (you can manually adjust all the ratios and stuff to suit your particular combo): http://www.geocities.com/z_design_studio/

 

Just as an example my old setup with 7000 rpm redline, 23.5" tall tires, 3.70 gears, and a Nissan 5 speed topped out at a theoretical 172 mph or so. It would never have gotten there unless dropped off of a cliff, but there was still plenty of room to adjust it higher by taller gears and tires if I wanted.

 

I just plugged in 285/35/18, 7000 redline, 3.55 gears and the .773 O/D ratio and it comes up with a theoretical top speed of 196 mph...

Link to comment
Share on other sites

How about the good ol r230 ?

I'm going with that, with a 2.94 ratio. By combining parts from an 300ZXTT and Armada rear, you can get tall gears. 2.94 , 3.36 . And 3.69 from the 300zx TT .

 

I rarely go to the track or strip, so I won't miss the low '60 foot time' type of ratios. On the street I should still be able to break traction even with the tall gears ( turbo LT1/ 4 speed auto, by summers end ) and the won't be embarrassed by the occasional cocky sport bike rider on the open freeway.

-Les

Link to comment
Share on other sites

Debating the merits of the R200 and R230 diffs kind of misses the entire point of this thread. It has also been covered to wretched excess in other threads.

 

I think the Ford 8.8 pumpkin in T-Bird/Mark VIII/Cobra/ or Explorer guise has a ton of promise. They're affordable, easy to find, and gears are readily available, as are limited slip options. There are also several spindle types to choose from.

 

FWIW: The Jag setup is H-E-A-V-Y, same for the 9". Cool for a street rod, not for a 2500lb sports car.

Link to comment
Share on other sites

Ad in Rotterdam has been fitting BMW third members to the vehicles he has been outfitting for competition in Rally Events. I will be in his shop in October with a new digital camera and hopefully can document his conversion for posterity.

 

This is the website for his shop:

http://www.va-motorsport.com/index.php?page=3A&Sbm=0

Link to comment
Share on other sites

Jon M. That calculator is fine on paper, but not so good in real world application...

 

John Tedder and Mark Icard, What are you guys seeing on the front and back straights at VIR top end?

 

My guess is that both these cars are gear limited to about 150MPH. This is just a guess...

 

My "Current" setup will use a Hoosier 275-35-18 which is 25.2 inches tall. The tranny is a TKO600 W/Road race gearing (1st gear is 2.87, 2nd is a 1.89, 3rd is a 1.28, 4th is a 1.0 and 5th is a .82) and the Current diff is the Q45 w/ 3.54 gears. I plan to spin the motor to about 7K RPM.

 

As SVEN said (Thanks Sven), The Datsun rear has been debated to death... Hence the title of the thread for this little excersise!

 

Mike

Link to comment
Share on other sites

Mike,

I installed a Quaife with 354 gears coupled with the GForce using the following ratios. 1st-2.94, 2ed-1.94, 3rd-1.34, 4th-1.00, 5th-.90. With 265-45-15 rubber and limiting my revs to 7K, mathematically, I top out at 150 in 4th and 166 in 5th. On the long back side at VIR, I will short shift into fith at about 6500 and then pull for a short distance before the lefthander. At that point I'm real busy just hanging on and that's about as fast as I want to be going in a 2400 lb z car. I like the higher geared 354 because I'm boosted. You na guys may benefit from a lower ratio and more rpms. The 354 gives me a fast 3rd ( 112 mph) that seams to work well for me but as we know, there is no perfect ratio that will work at all the tracks. I haven's used the new gears at CMP yet but I will be able to try them this weekend. The old 370 rear with a nissan gear box, had too low in rpm in 2nd and 3rd at CMP, but the new setup should give me better lap times. As Mark mentioned, I had custom axle shafts made that are 7/8" shorter that the stock lsd ones. This enabled me to run the axles in the original position, without reversing the ends, which I believe, was causing binding and cv failure under heavy compression. The installed lenght of the new shafts is 1/2" shorter the the reversed end setup. Now, all seams to be fine and dandy back there. To be continued.

Link to comment
Share on other sites

No functional speedo here, but according to the datalogger 152 on the front straight, don't know on the back. Mark is faster than I am.

 

Available R200 ratios force the use of an overdrive trans, which eliminates a jerico type. My TKO has the 0.83 OD, and I haven't found the end of it yet, I think it calculates to 172 or so.

 

jt

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...