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Driveline Weakest Links M6

2K views 7 replies 5 participants last post by  thewrx 
#1 ·
Was just wondering, if anything was to break in a manual driveline what would it be?
Assuming no wheel hop and a high rpm launch with traction N/A

  • TR6060 trans is strong and rated to cam/heads NA power. Cross this off.
  • The clutch life is dependent on how much slip, i.e. heat. But will never instantly fail. More gradual failure.
  • Tailshaft / Axles. Has anyone heard of these breaking? Are these strong enough?
  • Diff. Usually a true track diff is strong enough for NA power. Cross this off as I'm getting it done.

In summary I'm thinking the tailshaft and axles, what are your thoughts? Should I replace these to be cautious?
I want a 1.5 - 1.6 60ft.
 
#2 ·
with my little 6MT high HP group, so far we have one broken driveshaft (900+ hp) and a broken axle (750 hp). both have major clutches. Meanwhile, I'm rocking an OEM clutch with 700ish HP and 70K miles. But, I'm not doing launches with sticky tires.

so, it all depends how you drive it. If you are launching hard with 600+, you had better have some upgraded components.
 
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#4 ·
The transmission is fairly robust, as noted.

The MT diff (or more specifically the limited slip unit) is a weak link. The minimal needed upgrade is the Camaro SS-1LE rear unit with the Eaton True-Track differential unit. Beefed-up billet side bearing retainers are also available for this diff. Also consider the Camaro Z28 rear cover with internal heat exchanger, which can be tied in to the transmission fluid cooling circuit (also as in the prior-gen Camaro Z28.

Replacement of the stock clutch with a stronger unit (i.e., Monster triple disc clutch) is a good upgrade, particularly if track work is planned (the stock clutch slips more if hot). Do Not Fail to replace the plastic clutch throw-out bearing spacer with the aluminum after-market part. This is one of GM's little "reliability time bombs" so thoughtfully included in the OEM car (like the rocker arm roller bearings and the stock valve springs).

The stock driveshaft is marginal but nicely quiet. Replacement with a one-piece driveshaft will be stronger, but is longish for bowing resistance. I have had not-good luck with aluminum (it tears). Steel with more diameter and more wall thickness should be adequately durable, but will be heavier and have greater rotational inertia to overcome. Carbon fiber has many desirable qualities for a one-piece shaft, but there is concern about proximity to hot exhaust components, The resin holding the CF together gets weak (soft) if overheated, a greater concern for a street car vs. a track car. My stock driveshaft has not failed yet, but my thinking is to try for a stronger 2-piece custom shaft of the same design if this happens. I also have purchased a new stock driveshaft as a spare.

The stock axle half shafts will not take excessive abuse, and don't include some of the "secret sauce" such as different torsional stiffness on each side to damp resonance. There are now much stronger, and better designed half-shafts available from the aftermarket.

A contributing factor to driveshaft and rear drive unreliability is the quite soft bushings and limber suspension members used in the rear suspension, The stock set-up allows excessive deflection, and consequently mis-alignment of drivetrain components while under heavy torque loadings. Installing stiffer bushings and more-rigid suspension members (e.g., rear trailing arms and rear toe links) will improve reliability (if not ride quality).
 
#6 ·
Thanks for the responses, helps a lot. If I only replace the axles and diff, would this put a lot of strain on the driveshaft? Am I better off replacing this at the same time to avoid it now becoming the weakest link?
Does anyone know if the driveshaft is the same one used on supercharged vehicles?
 
#7 ·
Something will always be the weakest link…match the components to your power level and driving style, then keep a “repairs” reserve in the bank.


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