chuckster

I have a 3.42 rear MN6.

There are 2 ways to make my car quicker.
1. Add more HP
2. Add 3.73 Rear

My question is this...

How much HP would it take to equal the thrust of the 3.73 Rear. And how much would that HP cost (not NOS)

Then I could compare the cost of adding more HP or changing the rear.

I realize that there is no HP gain with a rear change and it's not measureable on a Dyno. But who cares, quicker is quicker. as the old saying goes..."Horsepower sells cars, Torque wins races" :D

Mike Mercury

There are a couple reasons why I am taking the axle ratio change versus mods to the engine:

1. GM Warranty. It would very difficult for a dealer to notice the axle ratio change. Although the M-M Warranty Act should protect you anyway, I don't want to take the risk.

2. Does not add stress to the engine with increased HP. No fear of a check engine light, no need for a MAFT; or ECM reprog on the MN6.

3. Rear carrier exchange is all done from underneath; no need for anyone to get under the hood... lean over the side and scratch the paint.

These reasons are for my mindset, and you may have other reasons to avoid an axle ratio change. Yes; I am taking the "safe" route :)

SteveL2

Mike,

I agree completely with your 3 points and they've been pointing me toward the rear end change also. But, on point 2 regarding the PCM, I thought I previously read that on an MN6 no PCM change is necessary, but in this thread there might be a suggestion that there could be PCM issues: http://forums.corvetteforum.com/zerothread?id=177865

Chuckster -- thanks for this post. I am trying to make the exact same decision, but so far there's not too many folks who seem to have timed comparos on acceleration before and after just the 3.73s (some did other mods at the same time).




[Modified by SteveL2, 12:26 PM 11/13/2001]

George Cooper

That post about the PCM reprogram was from L.A.P.D., but it wasn't clear whether it was intended for the M6 or the auto. Hopefully, they will respond and clear this up. I don't know why you would need to mess with the PCM on an M6.

TAL

From what I understand you will need a PCM reprogram with either the auto or MN6.

I have been toying around with the idea of 3.73 gears for the Hardtop. I am very happy with my simple mods I have done and don't want to affect any drivability. I'm even happy with the stock exhaust! Although the Z06 catback would be nice!

Going to a 3.73 would give a virtual 2.95 first gear doing away with the pathetic 2.66 gear we are saddled with. The reason why the Z06 has such great acceleration is the 2.97 first gear.

From what I have heard Motive Gear is supposed to come out with a 3.42, 3.73, 3.90, and 4.10 gears for the C5. West Coast Corvette has the dibs on this product but their contract will expire from them in 6 months. The gears from Motive Gear are the ring & pinion type which will be MUCH less expensive than the whole rear section that you must buy.

Motive Gear promises they will just as quiet as the OEMs but your installer MUST be good at installing gears because any misalignment will result in noisy gears (ie howling).

I hope these gears are much less expensive than the whole carrier...

Peach

Doing both, take no chances :cool:

Austrian Vette

Yes!!!:D

Michael

SteveL2

Chuckster -- forgive me if this is common knowledge, or if I'm getting this all wrong, but here's a thought. I just came across a post elsewhere, and not related to vettes, but it defined torque, at the peak of HP, as:

peak torque = (peak HP) * tranny gear size * rear end gear size

So, it sounds like the biggest "fun" out of this rear swap is insured so long as the rear end size goes up by a bigger factor than the peak HP goes down. In other words, I've read on other posts that the 3.73 gears actually make HP go down, but I think it's only on the order of less than 3%. On the other hand, a swap in gears from stock 3.42 up to 3.73 is an increase of 9%. As a result, peak torque goes up. This should explain Mike's excitement, provided I didn't get it totally wrong.

Peace.
:cheers:


[Modified by SteveL2, 3:30 PM 11/13/2001]

kewlbrz

The reluctor for the speedo pickup is located on the rearend.

An Auto requires PCM programming to adjust for shifting and torque control I beleive.

the MN6 requies no such programming.

vette-crazy

I'd add HP. The lower gear is only going to cause wheel spin. You will ultimately need HP/TQ to win a race. I believe SW uses the 3.42 rear gear.

kewlbrz

SW uses the 3.73 in his black 9 second FRC. He does use slicks tho.

HP (power) is what wins races. Not torque. HP is a function of Torque and RPM.

thekev_2000

I do not think this is correct, I installed a set of 3:73 in my car along with a new Cartek clutch 3 months before I had my engine work done and I did not have any issues with my MN6. I can not speak as it relates to the automatic...but if I had to guess I would say YES you need to reprogram for an A4.

When in doubt do both,......I think someone else said that also :lol: :lol:.

Good luck with the hardest part....the decision :cheers: !

SteveL2

I read a thread on the viper forum where an owner of both a Z06 and a viper asked if others agreed with his observation that stock for stock the Z06 hung with the viper through 2nd gear. Setting aside the barrage of nasties that ensued arguing Z06 vs Viper overall, it seemed the consensus was that the Z06 gearing was highly beneficial until about 70 mph. If this is true (and I haven't a clue if it is), wouldn't the 3.73 greatly help the non-Z06 at least until the 70 mph range? In other words, sure, added HP is wonderful, but when you say it wins races, does that mean really from about 70 mph on up? Thanks for any elaboration. :cheers:


[Modified by SteveL2, 8:37 PM 11/13/2001]

chuckster

Um... The original question was...How much HP = the 3.73 gears. Wheel spin Schmeel spin....I'll get drag slicks. :D

I am looking for thrust. I am sure I will do a cam eventually but..

Lets say I install the Hammer cam right now. Will I run the 1/4 as fast or faster than If I did the 3.73 :confused:




[Modified by chuckster, 9:44 PM 11/13/2001]

C5Noir

I want 4.10's, not those cheesy 3.73's :D (JK). But really, 4.10's would be the ultimate kick butt setup for street/strip :).

KingTut

Nobody has mentioned Heat and Noise. Most of the more horspower mods increase the heat around the engine (ie in the drivers seat) and the increase in noise from headers, less restrictive exhaust, etc. The gears are completely non noticable except you jump off the line quicker than the other "stock" guy.

Maybe we are talking about "Quicker" vrs "Faster". Win in the 60, lose in the 1/4. For my street only money - I take quiet quickness.

C5Longhorn

How much do 3.73's affect top end? I personally would prefer more horsepower. Good luck with whatever decision you make.

jschindler

I've watched an 02 Z06 stay with a Viper from second gear roll on to about 90mph - more than once. In fact, the same cars, I've been told, ran together from a dead stop also to about 90 or 100 (in all cases, they backed off by about 100). I watched the roll ons, and both drivers confirmed this info.

WestCoastCorvette

Gota call yesterday on 3.73, 3.90 and 4.09 gears available. Looks like the pricing will be about $1500 a set . Is anyone interested? :eek: :eek:

kewlbrz

3.90? 4.09?

West coast corvettes tried to do the rebuilt factory rearends, with 3.90's which had to be shoehorned in. Most the concern was reliability because after 3.73 the gear sizing and number of teeth really begin to degrade strength. 4.09s?? How in the world? is this in a stock sized getrag carrier?

The great thing about the 3.73's. The only ones built and put together by getrag for performance purposes with hardened components are the ones you see in group purchases. And price is for the whole unit. Np exchange.

What is the offer you are talking about? Exchange? Just rebuilt with different gears?