What to do for a race car?

[datzenmike]

Weld it up. Deal with the under steer by modifying the suspension. Wheel spin is lost time. Spread the power to two tires.

 

Understeer Corrections

Drive a different line.

Use weight transfer to your advantage.

Push, plowing, front tires slide out first.

Usually slight under-steer is safer.

Raise front tire pressure.

Lower rear tire pressure.

Soften front shocks.

Stiffen rear shocks.

Lower front end.

Raise rear end.

Widen front track.

Install shorter front tires.

Install taller rear tires.

Install wider front tires.

Install narrower rear tires.

Soften front sway bar.

Stiffen rear sway bar.

More front toe out.

Reduce rear toe in slightly.

Increase front negative camber.

Increase positive caster.

Soften front springs.

Stiffen rear springs.

May need more front suspension travel.

Install wider front wheels.

Use softer front compound if possible.

Use harder rear compound if possible.

Remove weight from front of vehicle.

Add weight to rear of vehicle.

High Speed. Increase front wing down-force.

Too much front brake.

Vehicle is TWITCHY at limit and hard to keep ahead of in the steering department.

Lower front and rear tire pressures slightly.

Suspension may be too stiff.

Shocks may be set too firm.

Tires may be old or hard.

Vehicle may not have enough suspension travel.

Vehicle may have a toe problem front or rear.

Increase negative camber front and rear if possible.

[HRH]

I've autocrossed with a welded diff, it's no fun unless you're in a go-kart. ;)  Besides, if you set up the suspension correctly you shouldn't spin because both wheels will still be on the ground.

[HRH]

If it was rally, then hell yeah, I'd have traction aids.  For pavement with lots of grip though, I don't think LSD is a necessity.

[datzenmike]

You can have both wheels on the pavement and still loose traction.

 

Can you lower the vehicle any more??

[HRH]

Lol, what crack did you smoke this morning Mike?! :rofl:  No, it's as low as it will go, I already have to worry about hitting speed bumps.  And I don't have enough power to break traction if both wheels are on the ground. :)  I'm about to head out to the garage and install this diff here in a second.  Hoping it goes as easily as I think it will.

[Lockleaf]

I don't want to sound like a douche, but are you sure you got an R180? As far as I've ever known only STIs have that. Everything else is R160. Even my svx only had r160. Otherwise, what car did you get it out of, because that is useful info.

[HRH]

Late model Subis.  '01 Impreza.  Looks correct.  I'll know here in a second.

 

EDIT:  Well shit.  I think you're right.  Dammit!  They look so close, I didn't measure.  Only about a half inch wider on the flange plates.  Going to eat lunch and yank it so I have it for comparison.

[bilzbobaggins]

what are your going to yank???? lulz

[HRH]

Anyone ever used a hardbody front diff R180 for the rear?  I don't know if the front diffs have a different ring gear or whatnot because they're running in reverse.  Forgot they also have that extension shaft housing.  Were the 720s R160s or R180s in the front?

[Lockleaf]

720 front diff is r180 and it works on the back. The link below shows how sealik set one up to use on a 510, but it should tell you what you want to know. Sealik did it, so you can probably pm him about it too.

 

http://community.ratsun.net/topic/55608-r160-to-r180-510/

 

They came in 4.38 often, but I think also in 4.11?

[datzenmike]

The ratio is stamped on the engine tag under the pass side hood hinge on the inner fender. 720s were 4.375 on the early 4x4s and 4.11 later. D-21s had lower numbers.

[KoHeartsGPA]

What kind of a guy would I be without furnishing pictures?!  ;)

 

Same guy without any Ratsun stickers... ;)

[HRH]

^ Ah hah, I see what you did there! :)  So you want to know what the difference is between an R160 and R180?  About a half inch taller, and a half inch wider.  I took pictures with the tape measure I'll upload later.  Short of it is lockleaf was correct, I got an R160.  Now the only annoying thing is I'm going to have to go to Pull and Save to find an R180 in the gear ratio I want.  Which means getting dirty and not having air tools and generally it's annoying.

 

My other thought is to make spacers for the R160 lsd I have.  It's only a 1/2" to take up, however the R180 ring clips are internal to hold the axle shafts, whereas the R160 diff the ring clips are on the axles.  The ring land on the axle is quite large comparatively, so I can't just take the Maxima shafts and put them in the R160 diff, as much as I'd like to.  So that means I'd have to dick around with shafts too, as the Maxima has 280zx like shafts, not 510 or 280z like shafts.

 

So at the moment, I may go take a look at the 720s.  Need to dig around on the net and find out what ratios came in the zx cars.  Unfortunately I think they're on the highway side too.  The one Pat had listed at Pull and Save had a 3.54 ratio also, which is what I have.  I think the elusive 3.90 could have been found in an automatic Maxima sedan, but so far that's just as rare as regular Maxima.  There is an '81 wagon at pns currently, but it's wagon, so solid rear.  Boo.

[HRH]

As I suspected, all the Z cars got pussy highway ratios coupled with close-ratio transmissions.  Plus they had extra hp.  Consequently, guess I'm looking for 720 front axles then.  Maybe I'll just stick a Pathfinder solid axle under the rear.   ;)

 

Here's a good Z rear end reference:

 

http://www.zhome.com/ZCMnL/tech/GearRatios.html

[LenRobertson]

Matt - I hit the Valley P&S this afternoon. I'm pretty sure I saw a 4X4 720. Not sure of the year, but I'm thinking '82. Dunno if it has a front diff you can use. Also a 280Z and a 280ZX as donors for the 2.8 block and crank you badly need. But if that throws you out of the stock engine class, might as well go for a VG30. You have all winter to install it. I'm sure Reg would love to weld you up some motor mounts. :lol:

 

Len

[Lockleaf]

Do 720 front axles share the same spline count as your maxima? Or are you talking about custom axle, like 720 inner and maxima outer?

[HRH]

Hey Len, I probably just missed you!  So I just got back from Pull and Save.  I still have it, yanked the front diff from an '84 720 in 40 minutes.  I'll be cleaning it off and inspecting spline count and axle shaft fitment in a bit.  Then opening up and cleaning/resealing/oiling.  I'm thinking it's the same spline count, but not sure.  From my countings at the rear wheel, it should be a 4.11 gear set.  The other 4x4 720 was a 4.375, which is just too aggressive.  4.11 is a bit more than I wanted, but it's the same as what I had in the 510.

 

Truck had 186,000 on it, so figure half that (93,000) for the front diff.  Just a wag.  Got blasted in the front, but not enough to hurt the drivetrain.  So there we go.  I'll eat dinner and then go play, see if I can't get the diff back in tonight.

 

That was the odd thing about that '84/'85 720 Mike, there was no info anywhere on axle ratio.  The tag in the engine bay didn't have it, nor did the tag on the door.  Funny, huh?  The early '82 had an axle identifier.  I just ended up putting a lugnut on the rear wheel and marking one of the bolts on the driveshaft, then counting turns.

[LenRobertson]

Matt - It would have been great to see you. But if I had been there to talk at you and "help" with the diff removal, I guarantee it would have taken you twice as long!

 

The only thing I found at P&S was an nice 14-3 8 foot extension cord I can use in my shop (for $2.00). Sometimes if I can't find Datsun parts I have to settle for scrounging in trunks and back seats. At least I didn't leave empty handed. And it is actually something useful, not another Datsun 1600 valve cover or Elephant oil cap that I have several of.

 

Len

[datzenmike]

Bottom line reads TRANS:AXLE...... FS5W71B................. HF41

 

F.....  floor shift

S..... special over drive

5..... number of forward gears

W.... Warner synchros

71... distance in mm between main and counter shafts

B..... shifter type

 

H ..... third member style differential.

F.......90mm ring gear diameter

41.....4.1(1)..... 43 would be 4.375, 39 would be 3.90 and so on

[HRH]

Exactly, but the '82 had HF43.  The '84 or whatever it was didn't have anything at all!  No HF number anything.  The trans was identified on the plate, but it's like they forgot to stamp it with the HF41.  Weird.

[HRH]

Well the fun continues!  The stub shaft out of the R180 in the 720 is indeed the same depth as the stub shaft in the R160.  Problem is, they're both about a 1/4" too short.  The Maxima R180 has probably a smaller crosspin which exposes another landing for the ring that holds the axle in.  I have all three diffs on the bench now, going to take apart the Maxima one first, and see if it's possible to use that center pin in the R160 and get the proper engagement of the Maxima axles.  I don't think this will work, but it might.  If it does, then I can make some spacers for the wheel bearing side that will allow me to use my R160 LSD in place of the R180.  Yes, it's a smaller diff, but it's plenty strong for 2400 pounds and only the 2.4l L motor.  I think Todd started blowing his R160s up at about 300 hp.  I definitely don't have that much.

[paradime]

  I think Todd started blowing his R160s up at about 300 hp.  I definitely don't have that much.

 

Yet!

[Lockleaf]

If this idea doesnt work, can you at least take ring and pinion from 720 and drop them in to your diff housing?

[510T]

The dust seal on the r160 axle needs to be removed / swapped for r180 duty. That should allow it to seat correctly.

[HRH]

Yeah, dust seal if using the R160.  I'm going to be using the R180 diff.  Taking the Maxima carrier and swapping it into the 720 R180 housing, then swapping the 720 crown wheel onto the Maxima carrier.  The inserts in the spider gears for the threaded hole that accepts the bolt to hold the stub axles interferes with the halfshaft of the Maxima.  It's about 1/4" to 3/8" longer than the stub axle insert.  Have all torn apart now, taking lots of pictures, they'll be up eventually.  Should have a working 4.11 gearset together and hopefully in the car by tonight.