Changing Final Drive Ratio?

[nearmiss]

I just recently bought my first Corvette - a Collector Edition with LT4/6spd - and am pretty happy with the way the car behaves. One question though for the forum is about the final drive ratio. This car seems to be geared really TALL. Has anyone swapped out the 3.45 for something higher (3.9'ish or 4.11?) and if so, how'd you like the change in performance vs cruising and overall feel of the car?

Thanks for the help,
Nearmiss

 

[Kevin Doyle]

I wish some one would answer this I'm wondering about doing the same.Thanks Kevin.

 

[LT4BUD]

Many people have done this and I don't recall anyone expressing any regrets. I went with 4.10 gears which gives you 73 mph in 6th gear at 2000 rpm. On interstate trips at around 70 mph I still get 26-28 mpg. Really improves 1st gear performance, but to be honest once you get to about 45 mph there is very little difference in performance. Most including my self view it as a good improvement. Sure makes the car a lot more responsive in low gear!! Bottom line is do it, you'll like it!!!

 

[nearmiss]

Hi Kevin,

I posted the original question here and over on the general 1984-1996 technical forum. People that have made the switch seem to like it. I did a similar gear change on a 5.0 Mustang and it really brought the car alive. The Corvette is geared even taller than the Mustang was. So, based on replies like LT4BUD's and others, I'm going to make the change as soon as I get the new tires paid for, since 6th gear is really pretty useless as it is now with stock gearing (and CHP using radar). Good luck.

 

[Skant]

The only downside, as I see it, is the potential for complications and annoying noises. I'm getting such straightened out right now. But man does the car wake up!

The biggest effect of the gearing is to make your 1st gear much lower and provide a much stronger launch. But even after 1st gear, your gears are still that much closer to eachother (the RPM ranges don't change, but the torque multiplication is still higher)... so it continues to make a (less obvious) difference throughout the range.

Of particular interest to drag racing is that the top of 3rd gear with 3.45 is about 104mph... and a stock LT4 will post a little above that. Which means you're facing the decision of switching to 4th a fraction of a second before the finish line... or letting it bounce off the rev limitter a fraction of a second before the finish line. Both of these harm your ET. With 4.10's, you'll be squarely in the upper part of 4th gear at the end of the track with a little room to spare (and a higher MPH than with the stock gears). Which is why this gearing is generally favored over the 3.73 gears for drag racing usage.

- Skant

 

[LT4BUD]

In the quarter mile stock, LT4's typically end up around 107-109 mph which is right at redline in 3rd gear.
With 4.10 gears red line is about 115-116 mph in 4th gear. Red line being 6300 rpm and rev limit is 6425 rpm.
So with 4.10's you will finish up in 4th gear at the dragstrip.

 

[kblack_LT4]

LT4 quarter mile

In the quarter mile stock, LT4's typically end up around 107-109 mph which is right at redline in 3rd gear.
With 4.10 gears red line is about 115-116 mph in 4th gear. Red line being 6300 rpm and rev limit is 6425 rpm.
So with 4.10's you will finish up in 4th gear at the dragstrip.

I find this interesting. I just ran mine twice this past week for the first time and it matched what car and driver and Road and Track ran in 1996. I ran a 13.77 @ 104mph and a 13.66 @ 105mph. Now it's basically stock(X-pipe, Corsas, and K&N) but I did notice the launch is touchy as you really don't have time to set your rpm to what would be optimal for launch before the lights change, and on power shifting 2nd, even with 3.15 tires, it still spins for a 1-2 tenth loss at least. I will (now that I have a helmet and it I can do more runs) do more this week weather permitting. But I am in forth, before the finish line. I do not rev it to 6200 rpm as it seems to be only pulling to 6000. I'm thinking with an optimal launch and an easier 2nd gear shift, it might run 13.4 - 13.5s. It's obvious to me if we could get past the wheelspin (drag radials or slicks), it would be faster but I'm sure it would shell the rearend after a little bit. One major problem is the temperature, it seems to run about 220-230 and I have a 160 themostat waiting but need the programmer to fix that fan issue, etc... I"d be interesting in hearing anybody else's experience with their stock or modified LT4s. I have heard of some LT4s supposedly running 12.90s. Never seen it and everybody in the vette club I talked to thinks it bogus somehow. But there could be some that just plain run better than others.

 

[NewGuy]

Just had my CE LT4 3.45 swapped out with a 4.11. What a difference, especially in daily driving. It feels like the ratio GM should have done if they were not concerned about gas mileage (same reason for the 1-4 trick)

Anyways, when you are going in city traffic, can stay in third all day long unless to a complete stop. In fact, I find myself shifting less since cornering in third is the perfect RPM range.

Never liked 6th gear before. Crusing at 70-80 mph with only 1800 or so RPM's felt like I was missing the torque range necessary if needed to make a quick response to something on the freeway. Rarely went higher than 5th. Now, happily cruise in 6th, perfect torque range and extrodinary response. Not a cheap swap job but if your rear end needs work (the car rear end), you would love the lower ratio.

 

[stgry1]

X-pipe??

. Now it's basically stock(X-pipe, Corsas, and K&N)

KBLACK..was curious where you got the X-pipe. I've been looking high and low with no luck. Thx

 

[NC-LT4]

4.10's

I am also a new owner of a '96 Silver CE. I haven't driven it much because the left front tire is showing it's guts on the inside tread. So tires, wheels and alignment are in order before the gear change.

I did a 4.10 on my 6 speed '95 Firebird and it is a great set up.
My questions to this group who have installed the 4.10's or made any other gear change is how did they compensate for the speedo. Also who did you use for a source for the gears?

Thanks

 

[Vettelt193]

Anyone do the shopping to find the best price on gears? I want to do the swap too, the only thing holding me back is the $$$. If I could at least get a decent price on parts it would make a big difference.

 

[Shriker]

I have 4.10's and they are just about perfect. With the tall 6th gear you still have nice highway cruising and mileage but much better acceleration everywhere else. Vettes are relatively expensive to do gears on because the rear is more complex than say a Mustang or Camaro with live axle setups. Still worth it though....3.73's dont feel like much of a change and there is no "real" 3.90something its a welded combo - I wouldnt trust that with much power.

 

[JEFNLSA]

What is a rough estimate on what it would cost to switch to the 4:10's from stock including labor....thx

 

[Shriker]

$800 would be a reasonably good deal.

 

[JEFNLSA]

Thx...good to know. 6th gear is more or less useless for me. That to me would be the best bang for my buck!

 

[nearmiss]

I have 4.10's and they are just about perfect. With the tall 6th gear you still have nice highway cruising and mileage but much better acceleration everywhere else. Vettes are relatively expensive to do gears on because the rear is more complex than say a Mustang or Camaro with live axle setups. Still worth it though....3.73's dont feel like much of a change and there is no "real" 3.90something its a welded combo - I wouldnt trust that with much power.

I have a 3.90 gear set in the diff and its from Dana: Dana 44 V, 44D/391V

 

[JEFNLSA]

How do you feel they stack up against the 4:10's ?

 

[nearmiss]

How do you feel they stack up against the 4:10's ?

I can't give you a direct comparison, since I haven't driven a 4.10 equiped 6 speed, but I really like the feel of my car now with the 3.90s. I was going to install a set of 4.10's, but the local Corvette Shop convinced me that I would probably be happier with the 3.90's based on the type of driving that I do. I do a lot of freeway driving at between 75 and 80 (or 85) mph with a little twisty road stuff and a bit of Mustang pounding for fun. My car is a daily driver to and from work, Home Depot, the grocery store, etc. I haven't measured my exact rpm vs speed yet, but I think I'm doing somewhere around 2.5K rpm between 75 and 80. My particular motor seems to be "happy" at that rpm when cruising. The down side is that 3.90 wasn't a standard ratio offered by GM on the corvette, so I had to trick the Hypertech Power Programmer using a combination of 4.10 ratio with tire diameter to get the proper speedo correction. Regardless, I couldn't be happier with the new gears. I would recommend that you try to find someone in your area that has 4.10's and go for a ride to see if you like the characteristics or if you find them a bit high reving.

Good luck and let us all know what you wind up doing!

 

[JEFNLSA]

"They" let you drive 75-80 mph in San Diego? I should move there! Unless I'm on a mission for a ticket I realistically can't go much past 70...at least not anywhere in the Phx area. I occasionally get on it and I feel like a man posessed but I'm watchin' my 6...big time. I appreciate your input yet for me the 4:10's will probably be better. My car is also a daily driver and I have a 70mi round trip commute each day. My car never sees 6th gear since the speed limit for a majority of the trip is 55. Right now, I've got 21K on it but that will soon change I'd love to find someone in the area w/ the 4:10's so I could check it out. I'd love to have that get up n' go around town. @#$! 1st gear is almost too tall for stop n' go traffic. Bad design for that car IMHO. If we could all drive around at 100+ then... right on ... but, that's not the case. 6th gear ...There's not an Autobahn around here:eyerole ...See ya !