MDL-01C5

I've posed this question in "other" places, but they're so busy trying to sell them that I'm not exactly confident in their honesty.
Unfortunatly, 95% of people here are F-body guys, and may know nothing of this, but I value the quality over quantity here anyway...
When aftermarket gears (made by Motive, I think) finally became available for us C5 guys last year, everyone was ecstatic-- as we've been limited to 3.73's for years...
They came out with 3.73's, 3.90's, and 4.10's.
Here's the issue:
Getrag, the people who manufacture the diff case, says that the case can not handle more than the 3.73's without breaking. They say they've known this since the case was designed, which is why they've only ever offered 3.73 as an upgrade...
This was big news when they came out, because people were afraid of breaking diffs (they're like $2000 for us, and buried indide the car--no pumpkin-swap ease for us <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> )...and low-and-behold, some of those who ignored the warnings and went with 3.90/4.10 ratios did indeed grenade their rear ends.
Case closed, right?
Well, No...
To date, they still sell these rear gears with enthusiasm, and evidently, (at least according to the 2 vendors that sell them), they've sold hundreds with no failures other than those few initially.... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
I want to know what you guys think of this...
I'm really tempted to swap into some higher gears within the next year..it would be a Godsend to the powerband I've got, but I'm not willing to do it on the sole assurance from the people who sell them or those that haven't (yet?) exploded them in their cars in the few months they've had them.
What do you all think?
Thanks <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

<small>[ August 11, 2002, 12:12 AM: Message edited by: MDL-01C5 ]</small>

Brother J

Sounds like a roll of the dice. How lucky do you feel? Personally, I'd go with the 3.73's.

P&DZs

iTrader: (1)

I'd been reading corvetteforum and seeing the initial pumped attention given the new ratios. However, as you said, since the things have been out I've not seen enough people/users touting how wonderful,long lived etc.. I'd have to hold off for the $$$'s that are involved for the C5 'till I'd seen more of a track record established by the early users(guinea pigs).

99 Black Bird T/A

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MDL-01C5:
<strong>Getrag, the people who manufacture the diff case, says that the case can not handle more than the 3.73's without breaking. They say they've known this since the case was designed, which is why they've only ever offered 3.73 as an upgrade...
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">If I had a vette and Getrag said that, it would be 3.73's for me.

Maybe after a year or so you'll get a feel for how well the diff case holds up with 4.11's etc and can decide then if it worth the risk.

meine96ws6

iTrader: (4)

I wouldn't see a problem with higher gears, its once you drive aggressively+ wheel hop then boom...you have issues.

Contact a reputable company...rpm for example, great reputation and have wonderful customers service..

And they did mine..

1 FMF

iTrader: (1)

my understanding fwiw for any gear case is that it has a torque rating which is based on materials and design of the case for starters.
The torque output from the engine is known for any given rpm, i.e. dyno graph. Just off the top of my head i'll use 400 lb-ft at 4000 rpm as a max. In first gear for whatever transmission ratio you have, I'll use 2.66 from the T56 for the math, the max torque leaving the transmission is 1064 lb-ft. So with a possible torque input of about 1000 lb-ft into the ring & pinion the differential case has to withstand that force and that torque gets multiplied further by the ring & pinion ratio and then the axles and tires see that output. it should be fairly easy to understand that if you had lots of traction and the heavier the vehicle, that increasing R&P ratio to higher number increases torque to the axles and with a high enough ratio you simply snap the axles, or blow the differential apart because the case can't handle the force.
If you said 3.73 R&P ratio was the max, google tells me the standard auto ratio is 2.73 and the oem performance ratio is 3.15 for the vette. 3.73 is an 18% increase over 3.15 which i assume is the max safe ratio, and 4.10 is a 30% increase. I'm sure the manufactures designed things and set limits, how much i don't know but i would guess about 20-25% meaning they knew what the max torque input would be given the engine and transmission package so they provide a differential case with a R&P ratio that would handle at least 20% more torque than it would ever see. If you go changing the R&P to what is a 30% increase then yeah based on those numbers you are going to have problems if you launch the car hard and have traction. so whether it's safe to run higher R&P ratios depends on how you drive, if you can consciously drive such a way you never exceed the torque input/output rating of the differential then you would be ok and that may boil down to not accelerating as fast as you can especially in first gear.
I can't see your pics or links above, under what conditions were those failures? If it was a pedal to the floor from 20 mph in first gear then i would be worried, if they were clutch dumps at the track then maybe not so much.