Recently I had the opportunity to run the car on a track at the AZPOCA INDE Track Day. We put the car together back in 2017 and it has been driven sparingly but have finally decided it's time to run it a bit. After a few laps it started to develop a noise coming out of the rear of the car. Strangely the noise only could be heard during the turns (both right and left) but nothing could be heard when running light or hard in a straight line. The volume of the noise started low and stayed low and increased with speed again only while cornering.
Some background: Gearbox is full 80/90 Pennzoil GL-5, Half Shafts rebuilt and spun balanced by a competent Drive Train shop, The ZF is an unknown but shifts perfect and has a reasonable lash. Liars Poker says the car has 53k miles. We have checked for excessive play at the rear wheels in both 3 and 9/6 and 12 positions and there is no noticeable motion of the wheels. All bushing and bolts were replaced at reassembly. Someone has been in the rear uprights before: the lower cross bolt area of the casting has grease fittings and they have flowing grease. The axle retention nut is the newer "flat sided" nut (W/O the crown as I've seen in some pictures).
I have reviewed the "Rebuilding The Back Suspension" from The Pantera Place referenced in several earlier Infopop write ups. This write up seams to best reflect the sound but I haven't found any rubbing as the author did!
Two popular scenarios have emerged: First is the Upright Bearings and secondly the the Differential section of the ZF.
First: I'll be rebuilding the Uprights! There appears to be 4 types of bearing configurations from my reading.
A) Stock type bearing replacements: 6208-2RS (40x80x18) and 6308-2RS (40x90x18) both have the rubber side shields on both sides.
B) Modified (no Machining Required) 6308-2RS or 6308-DDU and a 3208B-2RSRTNG (30.2 wide double row BRG for the inner; Wilkinson is mentioned with this variation).
C) Modified (no machining Required) Dick Koch design utilizing double row tapered roller bearings. Apparently this design is only on a couple of cars and information is scarce.
D) Modified with machining involved! Dual Tapered roller bearings which I understand is the "Bullet Proof" option! And again little information can be found on this modification.
The questions:
Have I listed the correct bearing numbers for option A and B?
Does anyone have any information on options C and D? I'd really like to pursue Option C as tapered rollers would be a better option without machining. I have resources to execute Option D if I can secure the information and the bearing numbers involved. But would rather not cut the upright castings.
Sourcing options for the bits, pieces and seals?
A side note while I'm in here with this torn apart: Is there a two piece inner hub and bolt on disc available to replace the stock brake rotor (clearance for 15 inch wheels with the 6 piston Wilwood caliper and park brake kit from SACC)?
Maybe a replacement stock disc drilled and grooved? We can reuse the stock disk but as I said we're in here.
Second: Going into the ZF Differential Section
Is there a ZF Manual that covers these gearboxes (ours is #4104 and is labeled type 2)?
Hoping this is not necessary but could be related!
Winter is coming here in Michigan and like it or not I'll have down time!
