Hey guys, so i have a quick question regarding the s2000 rear diff. My father has an s2000 and when he bought it, the previous owner had installed a 4.77 gear set. Now the car is FI and the gears are more of a hindrance than they a worth. He is thinking about switching out the final drive back towards stock but is curious about the power handling ability of the stock diff. The car is making about 350-360 to the wheels but is taken care of quite well. Its dragged every so often but no serious abuse. The question is, what would you guys do if you were in this situation and what are the options? I guess the simple plan would be to put in a stock gear, then an alternative would be to put in some sort of custom stock ratio forged gear or throw in a different diff (most of the s2000's use some nissan diff??). Thanks for you input guys!

 

Well, if all he has is the gear replaced then it's not much stronger then a stock diff. Does he have a reinforced housing or anything? We need more specs on what he actually has now.

I'm sure there are a number of people who would trade him there stock diff + cash for his geared one.

Inline pro offers a kit that allows the use of the R200 diff out of the Nissan 240sx (as well as a few others). The kit is pretty expensive... It includes custom mounts, a custom drive shaft, and custom DSS axles. You have to source the diff housing and actual differential on your own. In the end you are looking at well over 2k for a nice setup. My ATS LSD for the R200 dif in my 240 ran me 1500$ alone and that was not with a housing... You don't have to replace the factory Nissan diff, but then you would be running an open diff and that's pretty lame.

 

i assume you could always weld the diff...thats what all my buddys who have 240's do anyway

 

^ thats just cause they dont have an lsd and cant afford to buy one so they weld it. a welded diff isnt such a good idea for dd or track cause the wheels are locked togather 24/7 this means when you take a turn both rears are spinning at the same rate and the car wants to go straight instead of turn. If your drifting than thats a different storry cause you dont need traction since your rears are sliding

 

and dont forget it makes the diff really REALLY noisy

 

350-360whp isn't too wild. I don't think I would go through the expense of a R200 swap.

PM s2kpuddydad on s2ki...he builds killer reinforced s2k diffs. I personally know one of his diffs has been holding up to a 600+whp car for about a year...not to mention a ton of dyno pulls for tuning. Puddy can build with either a stock 4.10 or if you want taller he can use a 3.90.

 

The diff housing itself is weak. So since he has a 4.77, the housing is more likely to break than with a stock gear since the torque is multiplied more with a 4.77.

If he has a re-enforced housing, it may be a different story.

But yeah.....you can trade someone the 4.77 diff for a stock diff and they'd probably pay you some $$ on top.

 

i think you got it backward. higher ratio mean it requires less effort to move the car forward which mean less stress on the diff. think of a worn clutch, it's more likely to slip in top gears where the engine has to work harder to more the car forward.

stock diff should be able to handle 350whp fine as long as you don't launch it. clutch dump is fine if the rear wheels break traction. if you do a low rev launch and the rear hooks, then bye bye diff. you should look into getting a reinforced diff if you plan to drag race.

 

With a higher diff ratio, it's easier for the engine, trans, and driveshaft to move the car forward. The diff and axles see more stress as they are at/after the point where the torque is multiplied. You're still moving a 2800lb object. The acceleration is greater. Which means that the extra work (torque) comes from somewhere.

The diff.

Making it easier to break with a higher ratio.

Think of it thsi way:

It's easier to move a bolt with a wrench with a 4ft pipe on the end of it. The wrench is, however, more likely to break that way. Plus, it will break at the point of the most torque multiplication. It usually breaks at the socket end....not near your hand.

This is pretty synonomous to your engine being the wrench handle by your hand. They're putting out the same amount of torque. The engine still transfers X torque at Y RPM into the trans. The trans ratios still multiply that torque by their stock parameters. The driveshaft still transfers the stock amount of torque as multiplied by the trans. The diff is where the most stress is. It has to multiply the allready multiplied torque.

In 1st gear, it's not unlikely for a 4cyl car to have 2000+ lbs of torque to the ground.

Ex: stock AP2 162lbs of torque at the flywheel x 3.13 (1st gear) x 4.1 (diff) = 2078.95 lbs/ft.

If your stock diff is prone to failure under stock torque multiplication (4.1:1), then it will be MUCH more prone to failure at 4.77:1.

 

If you decided to piece together an R200 conversion, I have a set of the DSS axles I would let go for cheap. You can find the R200's for really cheap, so all you would need other than that would be the driveshaft and mount kit.

It wouldn't be too bad piecing it together like that.

 

are you talking about the differential unit itself or the rear diff as a whole unit? as far as i know the differential unit itself is not the week point but the bearing caps that holds it in place is part that is commonly broken (although i have seen pictures of broken pinion and ring gears but i think that was the after effects of broken caps). i understand your view and i agree that the differential unit itself does see more torque but i look at it this way. with a higher gear ratio, that means it's easier for the pinion gear to turn the diff unit, which means less stress between the pinion gear and ring gear and the pinion gear will not push the ring gear back as much and will not cause the bearing caps to break. my point of view is the load on the bearing caps and not the differential unit itself.

i don't really want to hijack this post any further. if you wish to discus some more, we can do it on PM or start an new post. thanks,