I am going to pick up a super hicas diff assembly and i was wondering what do i need to make this all work in my 93 240sx hatch w/o abs? Can i just take my diff case and just put in the vlsd and just use my original axles and drive shaft?
Thanks
Swaping in abs VLSD
-
Hijacker
- Posts: 14373
- Joined: Wed Aug 13, 2003 4:57 am
- Car: '92 240sx Convertible
'94 F-150 - Location: Fredericksburg, VA
if you want to make it easy on yourself, grab the driveshaft too. the ABS shafts are slightly shorter than the non-ABS units. Taking the VLSD and putting it in your diff case is easy, but it's time consuming, and expensive if you don't have R200 shims lying around.
Basically, there are preload shims placed between the diff bearings and the case that put resistance on the differential. Once those are chosen correctly, the backlash needs to be figured up properly. The backlash is the amount left or right the diff sits. You can shift it left and right, by increasing/decreasing the thickness of the preload shims.
Once all that's done, then you have to check the gear teeth contact patch. You do this by placing prussian blue on a few of the ring gear teeth, and then you spin the diff from the input shaft. I find it easier to spin it with a power drill that has the proper socket attached to it.
What you check for are light spots on the gear teeth to see if they leave a comet shape. A fat head on the inside that tapers off a thin tail. If the comet isn't centered properly, then you need to adjust the pinion gear height. Which means you need a new set of preload washers for the pinion gear.
Oh, and the preload washers aren't cheap. The side shims are 16 a piece. You will need around 6 of them, and you only end up using two.
Or, you can grab the driveshaft and make it a lot easier on yourself. Don't forget the stub axles
Also, if this is going into an S14, you'll needto swap your S14 rear cover onto the S13 carrier
Basically, there are preload shims placed between the diff bearings and the case that put resistance on the differential. Once those are chosen correctly, the backlash needs to be figured up properly. The backlash is the amount left or right the diff sits. You can shift it left and right, by increasing/decreasing the thickness of the preload shims.
Once all that's done, then you have to check the gear teeth contact patch. You do this by placing prussian blue on a few of the ring gear teeth, and then you spin the diff from the input shaft. I find it easier to spin it with a power drill that has the proper socket attached to it.
What you check for are light spots on the gear teeth to see if they leave a comet shape. A fat head on the inside that tapers off a thin tail. If the comet isn't centered properly, then you need to adjust the pinion gear height. Which means you need a new set of preload washers for the pinion gear.
Oh, and the preload washers aren't cheap. The side shims are 16 a piece. You will need around 6 of them, and you only end up using two.
Or, you can grab the driveshaft and make it a lot easier on yourself. Don't forget the stub axles
Also, if this is going into an S14, you'll needto swap your S14 rear cover onto the S13 carrier
Re: (tenkawa_akito)
So i can't use the stock shims and stub axles that are on my car?
-
Hijacker
- Posts: 14373
- Joined: Wed Aug 13, 2003 4:57 am
- Car: '92 240sx Convertible
'94 F-150 - Location: Fredericksburg, VA
you might be able to use the shims out of the VLSD carrier, but you never know what the total diameter of the non viscous carrier is. The tolerances are so precise, it's mind boggling.
Case in point. I swapped a VLSD unit out of a silvia into my carrier, but the old shims from my open diff were too thin. The preload was so light, I could easily spin the diff by hand when the ring gear was off. I changed thickness by only a few thousandths of an inch, and it made all the world of difference for the preload. It took a little force to get it to spin.
As for the stubs, non VLSD stubs will not work with a VLSD. The VLSD stubs are longer, so they can engage into the viscous coupler.
Also, if you do decide to go the swap route, swap the ring gears too. Even though they're the same, the ring and pinion have had a lot of miles to settle into each other, so it's easier on the person rebuilding the rear end to use the same ring/pinion combo.
Like I said, it will be tons easier to just grab the driveshaft out of the donor car.
Case in point. I swapped a VLSD unit out of a silvia into my carrier, but the old shims from my open diff were too thin. The preload was so light, I could easily spin the diff by hand when the ring gear was off. I changed thickness by only a few thousandths of an inch, and it made all the world of difference for the preload. It took a little force to get it to spin.
As for the stubs, non VLSD stubs will not work with a VLSD. The VLSD stubs are longer, so they can engage into the viscous coupler.
Also, if you do decide to go the swap route, swap the ring gears too. Even though they're the same, the ring and pinion have had a lot of miles to settle into each other, so it's easier on the person rebuilding the rear end to use the same ring/pinion combo.
Like I said, it will be tons easier to just grab the driveshaft out of the donor car.