argonaut

I finally made it to Wakins Glen, a track I've always wanted to drive. 3rd lap of first session my differential starts whining horribly and smoke fills the cockpit. I pulled it into the pits and found oil dripping badly from left side, I think it may have been out of the vent. I drained the oil and it was full of metalic particles.

I've been running this car pretty hard with no cooler on the diff or trany. Don't know if this is the cause but I think I'm going to go ahead and put both coolers in now.

At any rate, I've done a little reaseach and would like some opinions on what to do:

- Gear Ratio - I've been using the 3.42 but now could go to 3.73. I drive Summit Point, Pocono, NJMSP the most. I wouldn't mind a little more jump out of the corners. Any thoughts on the ratio?

- New or "built" Rebuild - I can get a brand new GM 3.42 Diff for $1300-1500. Or I can get a DTE or RPM "Stage 2" for $1795 (3.42 or 3.73). What do you guys think, is it worth the extra money to get a "built" one.

- Based on some past posts I have read, I do not think I'm interested in the Quaife diff. It doesn't sound like a good option if you like to trail brake. But...If you have a Quaife I'd be interested in your thoughts.

EDIT: I have a 99FRC with approx 390 RWHP. Thus its the MN6 tranny

Thanks a bunch for any info - Brad

geerookie

What do you have? Coupe or Z06?
I have a '99 coupe (stock motor) and run a 3.73 gear. Since I'm down on power compared to the z06's it does help out of the corner BUT I run out of gear everywhere! I find my self having to short shift and ending up in 5th gear in many places which with the coupe is a handicap on the long straights (over drive and low horsepower).
In a Z06 a 3.73 may not be such a bad idea as you have a higher rev limit 6500 vs. 6000 in the coupe. That 500 rpm would fix some of the shifting I have to do and with more horsepower and a lower 5th gear it may work out for the better. It may also make 1st, 2nd and 3rd to short...something to think about.
I think I have decided when I replace my rearend I'm going back to a 3.42 AND up my rev limit to 6500. I have been running slicks and I can get them in a 25" to 27" diameter range so I will go a little shorter.
This is my experience over the past 4 years of running 3.73 gears.
Also I will probably just get a blueprinted diff from Phoenix for $950.

CHJ In Virginia

That really sucks to have the failure so early in the event. The Glen is a marvelous track. IMHO I would spend the extra $ (not that much more) and get the built RPM differential. Stay with the 3:42 gears. You can check with AlohaC5 on the forum, he also swapped back from 3:73 to the 3:43 gears for the same reasons in the first post. He had to shift into 5th too many places and it was hurting times.

0Vector Vette

I would recomend Zip Products, that's who builds my diffs. Give Justin Abbott a call, 1-800-962-9632.

Robert

96CollectorSport

Figure out what your minumum and maximum speeds would be for each corner of each track you drive (if you can do it) If you can't figure out the speed try to think where you were running out of rev's and had to short shift or coast.If you go to this site http://www.f-body.org/gears/ you will find out how much of a gain or drop.
All you need are the tranny ratios (MN6 1st-2.66, 2nd-1.78, 3rd-1.30, 4th-1.00, 5th-.74, 6th-.50) then put in your tire size and rev limit and compair the different axle ratios.
Hope it helps.

geerookie

Here's the one I use. You can choose which model car and tranny at the bottom. Also compare RPM ranges and tire sizes. Be careful...you can spend way to much time playing with this! Either the wife will start wondering what has your attention or you will have so much data you can't make a decision
http://xse.com/leres/ss/calculator.html

argonaut

Thanks for the inputs. Should have mentioned in the orginal post - car is a 99FRC with the MN6 Tranny.

AU N EGL

Bob from ECS has run many different Diff ratios on several tracks. I think he started with a 4.10 then went to a 3.73 and settled on the 3.42.

We runs at the Glen quite often.

AU N EGL

really. Zip is only a few hours north of me out side Richmand.. I buy a few things form them and bought my trailer from the place next store to them.

Can they do Transmissions too?

0Vector Vette

Tom,
They don't do transmissions yet. They have been doing diffs for years. They have built all of mine and did Leighton Reese diffs when he was running World Challenge. They can even do Quaiffe diffs if you like.
Robert

71corv

If you want to see a good example of Zip Product's work,see the September and October editions of "Vette" mag.

Gene

DTE Powertrain

Hi Brad..

We've built high performance differentials that have competed and set a Corvette World Land Speed Record at the Bonneville Salt Flats in 2007 (236.66 MPH A/BGT)- not to mention making multiple 250+ MPH passes (behind 1400+ RWHP) this year there also in that same car, so we have the expertise and knowledge base to configure you a durable, low-drag, race-winning HD differential to withstand very high powered applications that operate in abusive, extreme-heat environments. In fact, a lot of what we learned building those Bonneville differentials over the years has found it's way directly into our street and road racing differentials to this very day!

Give me a call when you get a chance and we can discuss your options to configure you a HD differential that will fit your specific road racing applications.

260-407-5455


Regards,
Phil

Wicked Weasel

I happen to be at this event with Brad and it really sucked he missed out on this. Nice guy and to watch him take apart the rear hoping it was only a seal to find metal in the oil was disappointing to say the least.

As far as gearing with your hp I would lean towards 373 over the 342 especially with the mn6. you will find places where you will run out of gear but I think the advantage of the 373 will outweigh the extra shift that you may have. When I had 460 rwhp with my h/c 346 I thought the 373 were a nice match. It wasn't until I went with the ls7 and 560 rwhp that the 373 just ran out in far too many places way too soon.



Of course everything comes down to personal preference.