Re: 4.10 gears...not what I expected.
 

From another perspective - the recent Mountain Run some of us did last week:

Shortly before doing the run, I had a chance to experience Brett's 350 LT5 thru (4.10s). There is NO QUESTION the seat of the pants could feel the increase in punch over my 3.45 cog (allowing a little to maybe an extra ≈ 30 hp for the bigger cams in Brett's car).

But, as others have said, 6th gear in the mountains was pretty much useless, except above 70 on flat stretches. I believe a bigger ratio would have been useful in the hilly terrain. Even with a lot of the time spent in 2nd and 3rd gears and sustaining 3000 to 4000 rpm** over some stretches of curves, there were times when I was dropping into 1st (remember altitude plays a role too). A little more "dig" would have been welcome; it would have put the LT5 into its sweet spot - above 5000 rpm+ more easily.

**From the perspective of lingering in the 3000-4000 rpm range, it occurred to me that would put an LSx or perhaps even the new LT1 (C7 motor) right in their sweet (torque) spot - assuming at or close to the same rear gear ratio. Those LSx motors' (torque) peaks earlier (at less rpm) compared to the LT5, and in that particular application they would out-pull the LT5s unless the ZR-1 had something like the 4.10 ratio to bring the LT5 rpm into its prime torque vs. rpm range too.

That said, the results from last year's running of the 1/2 mile in Monee clearly showed where the LT5s shine. As Pete mentioned, the LT5s are obviously long-legged; pretty much dominating LS motors at that event in spite of the LS boys having a cubic inch advantage. (limited to NA motors, that is). I would attribute that to the fact that venue favors motors with peak hp in the high rpm range. The 3.45 geared Zs did very well for themselves! But, there were reports from the 4.10 geared LT5 guys that in that venue the cars would nose over when hitting 5th gear (somewhere above 120 mph).

So, the 4.10s in any one gear will increase torque at the wheels, and thus acceleration - in that gear, taken on the whole in a distance/speed venue vs. a hilly/twisty course (with altitude tossed in) ether the 3.45 or the 4.10s have their special place.

For now, I will admit the 4.10s are fun, especially on the street. But, taken on the whole - the extra shift in the 1/4 mile mitigates most of the advantage of the 4.10 gear for the ZR-1; at least for that venue (maybe if one power shifts, the extra shift could maybe be overcome to result in favor of the 4.10s...but not with MY ZF transmission - thank you very much!!). AND, hitting the 1/2 mile at the top of 4th with the 3.45 - is about as ideal as you can get for that application.

The 3.45s are evidently pretty good "all round" for speed/distance up to 1/2 mile contests (sans possibly power shifting). However, for mountain thrills...the 4.10s would have been VERY nice to have. It boils down to the venue, I recon. Too bad we don't have quick-change rear differentials like we had in modified stock (dirt track) racing. In under 20 minutes you could change the ratio to fit the speed/rpm equation for that track.

I'm thinking I'd love the 4.10s for street and cruising the twisties. But, for speed/distance contests, the 3.45s - up to 1/2 mile - it's pretty hard to beat the versatility. Even if one goes with a compromise between 3.45 and 4.10 (or 4.30s?) that gear too would favor certain venues at the expense of some other. Decisions, decisions....:( Maybe the answer is to have multiple Zs, each with different ratios and simply choose the Z that fits the situation. Yeah... I LIKE that idea!

Re: 4.10 gears...not what I expected.
 

It seems too much might not be enough, meaning the extra shift into fourth gear is offsetting any positive impact of torque multiplication when using the 4.10 ratio. Why not use a 3.73 ratio which will give a smaller torque multiplying advantage, but will keep you in third gear in the 7000 rpm range through the traps.
And so it goes....Jim

Re: 4.10 gears...an update on my conclusions.
 

So, I've had these new gears for a week now, and I am ready to amend my initial comments. Those comments, as I've said earlier, were based upon overly-inflated expectations that had gone unrealized. I also want to reiterate that I know Marc's "18% more torque" claim is 100% true. I NEVER doubted Marc and never wanted to give the impression that I doubted him and if I did that, I apologize to all, and especially Marc. My point was that I didn't FEEL 18% more torque, not that I thought it wasn't really there.

1) The car moves away from a stop much more easily and requires less slipping of the clutch. It gives the impression of a smaller, lighter car.

2) As Marc says, it does get to the "meat" of the power band more quickly, which is great.

3) The upper gears are definitely more useful.

To anyone considering this gear change, my advice would be to consider it more of a "driveability" upgrade than a "performance" upgrade. In my opinion, the overall character of the LT5 does seem to work a little better with the shorter gearing, which lends credence to the claim that the engineers originally designed this drivetrain with these gears in mind. Just don't expect the thing to take flight the first time you hammer it, like I did!

Re: 4.10 gears...not what I expected.
 

Yeah... That's where hp elbows its way into the discussion. For example, I (and several others here in FBI country) are @ or above 500 hp. I go through the traps at 121 mph and just as my shift light comes on (at 7100 rpm). A 3.73 would require a shift to 4th before the traps.

However, a 3.73 may be correct for a stock motor. When mine was stock, I ran 112 mph in the traps at about 6600. A 3.73 might be a good stock motor ratio.

This echos back to what Lee says - that being power mods are what makes the big difference, at least in the ZR-1/ 1/4 mile performance.

Re: 4.10 gears...not what I expected.
 

Here's another food for thought.
Two ZR-1's run same 1/4 MPH one has 4.10's the other has stock 3.45.
Guess which is winning from a 40-50-60-70-80-90-100 roll.

Pete

Re: 4.10 gears...not what I expected.
 

Im not a fan of steep gears myself. I have a little explanation that I tell people that Includes a Sumo wrestler vs Chuck Norris if anyone would like to hear it lol.

Trying to be as short as I can.. but to me gears are great if you are running 1/4 mile and 'quickness' means everything to you. If you can hook first gear, that steep ratio will help launch way harder and you will shave a noticeable amount off your e.t. For all other speeds besides launch gears are useless. The way I see it comparing 3rd gear with 4.09s and 2nd gear with stock gears is more relevant. Look at the speeds of those two final drives and you will see the multiplication difference and at the MPH that it occurs. People fail to take into consideration that yes gears multiply torque, but you are going slower in those gears. So 3rd feels faster.. but now you are only going the same speed as 2nd used to get to. SO really is your new faster 3rd much better than the old 2nd? that's how I see it.

Also the zf is a 5 speed + massive overdrive. reverse shares the same synchro as 6th so using 6th to accelerate [-X. Don't ask me how I know.

On my LT4 that spun 8k I dropped from 4.30 which was a waste of tires gear to 4.09. Which effectively made my trans a 3 speed (1-2 were useless) and went down to a 3.73. WIth the target troque being so high it effectively killed torque in the low range which was my goal and helped hook 1st gear on street tires. I also trapped 128 mph on low profile 19s at 44 psi on a road race suspension. Most races were well over in 4th anyways which was perfect since it topped out around 275 ish km/hr. Let the torque do the work which is what I like to say :)

Theres a reason the c6 z06 went numerically lower with a final drive. Torque. let the torque do the work. The viper is another example. It has a numerically low gear ratio (1st gen anyways) why? because its a truck motor and it doesn't like to rev. give it less gear and let the torque do the work. Its no secret viper owners got brainwashed by all the gears bs and put 4.10s and went to the track and went slower. In my opinion its one of the biggest mistakes people make with high hp/torque cars and why some dyno queens just cant make the mph and times on the road.

Re: 4.10 gears...not what I expected.
 

This echoes what a lot of folks homed in on with the 4.6 DOHC Cobras. A 3.73 or 4.10 was kind of considered what should have been the stock gear (3.27s in my year) but for 1/4mi work the conclusion was 4.30s or 4.56s - the mantra became "Don't fear the gear!". Apples and Oranges sure, but the curves, character, peaks and limits are similar. Note I did not say similar NA power!

Please note the above is secondhand but as a part of that community I watched a lot of efforts reaching that conclusion. I was autocrossing in stock class with my '99 so a gear change was something I could only lust after.

Now with the red car in *SP class I can, and hope to (someday) go to the 3.54. A lot of work for not much gain but still it is a gain, and that's racin'.

Cheers,
- Jeff

Re: 4.10 gears...not what I expected.
 

Curious, what PCM were you using on your 8000rpm LT4? Aftermarket? Stockers shut down after 7300-7400rpm.

The other reasons why the ZO6 and Viper went with a lower rear gear, was to be able to reach their top speeds with teh available transmissions.

Re: 4.10 gears...not what I expected.
 

All else equal, the 3.45 geared car will win from a roll. Unless you are rolling on in 5th gear.

Re: 4.10 gears...not what I expected.
 

If I had no idea what a ZR-1 was, and I was to go back and read this thread in its entirety, I would conclude that the ZR-1 serves one primary purpose: a 1/4 mile drag car. Virtually every poster mentions, above all else, 1/4 mile time, rpm, etc. Granted, I was curious as to whether any back-to-back acceleration comparisons had been done with the 2 gearsets, but I didn't change gears to ensure that I went through the trap at a specific rpm. That's just me, though.

Not saying there's anything wrong with it at all; I'm just kind of surprised that rpm in gears seems to be the most important factor in a potential gear swap. Just my observation.

Have a great holiday weekend, all! :cheers: