Install a Quaife LSD in my new-ish 915 or buy a rebuilt, but used factory LSD box

[juicersr]

I am in a quandry as to weather to install a Guard LSD (sorry about the typo in the header - going with a Guard, not Quaife) in my realtively new, smooth shifting 915 (i installed it as an exchanged, rebuilt unit in my SC 8 years ago and have put about 20K+ miles) or purchase a documented rebuilt, factory LSD 915 with 20K non-track miles on the clock. The seller claims that it shifted great when he pulled it recently, but he did not do the rebuild, and has the shop rebuild sheet.

When all is said and done with the Guard install, and if no bad gears, etc are found, i am going to be set back about $3000 in parts and labor. The used but rebuilt 915 is about half that.

What would u guys do?

Guard's are supposed to be the $hit, but is it worth it?

What is the lifespan on a well-rebuilt factory LSD tranny, assuming it wasnt abused? I keep hearing things about how mediocre and problematic the factory LSD was.

[juicersr]

BTW, the factory box LSD is an earlier (70's) unit. This is the good 4-plate unit, right?

[sc_rufctr]

I would keep the gearbox you have an buy the Guard LSD and have it installed.

I know it's the more expensive option but before you decide you should consider...

Even though the early 70s gearbox has shop build information you still need to verify the information on the shop build sheet with the workshop that rebuilt the gearbox...
But the shop that rebuilt the gearbox may not have that information on hand. That depends on how organised and professional they are.

With the Guard option you also have the benefit of knowing it's a brand new unit with a good reputation.
Others may disagree but I've only heard good things about "Guards"
And obviously your gearbox has a known history...

That would more than justify the additional $1,500 to me.

[juicersr]

Thanks Peter, kinda feeling the same way.

Is a rebuilt early factory (ZF?) LSD that great anyway?

[sc_rufctr]

I don't know much about the earlier gearboxes or LSDs. But I do know the 915 got better and better as the years went by up until 1978. Then it pretty much stayed the same until the G50 was introduced.

One of the most significant changes was the adoption of the smaller input shaft bearing (diff side) that cured the notorious "shagged" pinion shaft bearing problem.

That happened sometime in 1984. Not all 915s produced in 1984 had this modification but in 1985 they all did.

So to sum it up: Get the latest 915 you can or keep yours with a known history.

[juicersr]

Didnt the late 80's have weak 2 plate LSD vs the earlier 4 plate version?

[Bill Verburg]

What are you going to be using the trans for?
street? stock early 4 plate 40% is great
track? the asymmetric GT 40/60 is the best
A/X? you'll want a gear type whether GT or Quaife doesn't matter.

The $ thing is a personal issue, For racing, ideally you'd want Wevo to totally go through the box but that would cost a lot more than $3k

[Peter Zimmermann]

Factory LSD weak? No way, no how! I have used three in my personal race cars (two were set at 40%, one at 80%) - never had a problem. Always used Kendall Three-Star Dino 80W/90 and Kendall LSD additive.

My shop took care of quite a few 915 cars fitted with LSD, many with more than 100K street miles on them. I never had to "fix" a factory LSD unit, but sure had to do a ton of synchros!

[Geary]

Why not get the rebuilt trans for your car, and the Guard LSD for your coffee table?

The early ZFs had the good friction discs that last for years ... and yes, that early model is probably the 4-friction disc unit (although any ZF can be rebuilt with 4 discs when using special thin plates).

It isn't often that the early ZF body breaks, but they certainly will occassionally:
http://images.thesamba.com/vw/gallery/pix/546978.jpg

[juicersr]

Thanks guys. This car is is mostly for occasional track/ DE, but with majority street use. Good to know that the stock units are robust. I havent seen the rebuild 'sheet' but can only assume for repair of stuff that usually goes bad in 915 and not LSD itself

Geary, LOL, not a big fan of the Guard except as expensive conversation piece?

BTW, if the factory LSD were set up higher at 80%, would it be difficult to 'reset' to 40%?

[Geary]

Originally Posted by juicersr

Geary, LOL, not a big fan of the Guard except as expensive conversation piece?

LOL ... No, I'm a huge "fan" ... I just said that because when most guys receive a GT LSD, they hate to hide 'em away in their transmission.

It's quite straightforward to change an 80% ZF back to a 40%.

BTW, I'm a bit curious about the topic header, as a Quaife isn't an LSD, and Guard & ZF certainly aren't Quaifes.

[juicersr]

Originally Posted by Geary

.

BTW, I'm a bit curious about the topic header, as a Quaife isn't an LSD, and Guard & ZF certainly aren't Quaifes.

Geary, sorry about that, but as i explained in the opening of the post, i screwed up and put 'Quaife' when i meant 'Guard' in the initial header (tired at end of long day yesterday), but the 'edit' function doesnt allow u to change the post header once it has been posted.