Rear Gears

[jonszr1]

[quote=kenthompson]I have a GV unit that I'm thinking about selling. The adapter is for a 4l80e though. Do they make an adapter to a ZF 6 speed?


I do believe they have an adapter for every tranny if you got a gearvendeor it might be fun to try it out on zr1. which unit do you have the deep sump ar the shallow sump. i believe an aparter run aprox 300. sure would be cool an 11 speed zr1 . mighjt have to have earl campbell leggs though

[UKZR1]

My diff has a leaking seal that I intend doing this winter. I am looking at changing the the gears as well. I was thinking 410's but with some of the comments on here maybe I should go somewhere in the middle.

I want to be able to use 6th gear. I hardly use it at the moment. Firstly at around 80mph its right where the B&B's resonate. I also hate the lack of pulling power the car has in 6th. As for mpg, I average under 20 anyway. A more useable 6th may even up the mpg.

I don't drag the car but would like a bit more pull but don't want to end up with a first gear that isn't much use either.

[HIZNHRZ]

I'm going to go with the 4.10 gears. I got as much information as I felt I could and when it came down to decision time, Marc provided his usual timely logic. He never said that 3.90's or any other alternative was not the way to go, what he shared with me is why recommends the 4.10s for a car with a stock bottom end...

Here's what I think I learned:
- Marc does not have a source for a high quality Dana gear set in the 3.90 ratio. Other manufacturers make a 3.90 ratio but he has not been able to make them run silently.
- Marc would happily install 3.90s if a slight turbo like noise was acceptable to me.
- Marc does not use the Viper gear, he uses the Dana gear which is from a truck application.

I looked at the transmission gearing and RPM and MPH with difference rear gears and difference shift points. With this information I had additional questions from Marc. The following is what I understood to be his response:

- My math was correct. With the 4.10 and 3.90 ratios the gear ratio drop of the transmission's 6th gear causes the engine speed to drop below the peak power band. Thus the car is RPM limited to top speed in 5th.
- Marc recommends the 4.10 ratio because my engine speed will be at about peak power (about 6200 rpm at about 118 mph) as the 1/4 mile is completed.
- We agreed that this is an ideal gearing strategy for a rookie drag racer.
- the 4.10 ratio calculates to an ~.3 improvement in the quarter. The net improvement, however, will be about .2 second faster because of the loss to due load and shifting.
- Fuel economy will drop from about 27 to 24 MPG in 6th gear at 70 MPH.

I understand that hope is not a good strategy. I hope I made the right choice. I did my homework and I feel like I'm going with a proven and solid approach. Half the fun, however, is learning from experiences; even the expensive ones that might not work out as planned. Just being able to consult with someone like Marc already has been a worthwhile experience. If I don't like the 4.10s, I'll change them. Good luck on your decision.

[blackjack]

i always tought the dana 44,being a popular diff,was available in any ratio below 10:1...although im satisfied with 4:10 ,i would still like to try 3:90...
someone once told me the richmond gears were not as good quality as the dana ones...anybody know of a quality gear vendor that would supply us with the different ratios for our z ?
bj
91/1735

[Aurora40]

Originally Posted by HIZNHRZ

- My math was correct. With the 4.10 and 3.90 ratios the gear ratio drop of the transmission's 6th gear causes the engine speed to drop below the peak power band. Thus the car is RPM limited to top speed in 5th.

5th is .75:1 and 6th is .5:1. So shifting will cut the rpms by 1/3.

Regardless of the rear end ratio, a shift from 5th at 7,200 rpm will drop the rpms down to 4,800 in 6th. That's way out of the power peak for these cars, and I'd think you'd have to have gearing one heck of a lot higher than 4.10:1 to pull that off. So I think for all practical purposes 6th gear would not be a top speed gear unless you have some ridiculous rear end gears, or some ridiculous amount of engine.

If you want to try your 4.10's out on the strip, let me know. I'd love to go before they close for the season.

[Greybeard ZR1]

You really can't go wrong listening to Marc Haibeck. I've had 4.10 gears (dana) in my car for over ten years now and I concur with what he said.

To a large extent the decision depends on your driving style more than anything else. If, while driving with your stock gears, you rarely use 6th and find it lacking in power at your comfortable highway speed, like I did, then the 4.10 gears are for you. Fabulous mileage was not my priority when purchasing a ZR1.
When I bought my car, I thought the acceleration was good, but not great in 1st. and 2nd. So I put in the 4.10's.+ a lightweight flywheel. Wow, the improvement was very noticeable, and worthwhile. And now I can drop it in 6th and not feel like I'm driving a 4 cylinder car. 6th becomes a usable gear, still with great mileage.
I occasionally drag race, and I wish that I had 4.56's for that. With 4.10's you can easily run the 1/4 in 4th, but with 4.56's you could use the entire LT5 rev capability.
3.73, and 3.90 gears are usually recommended for big inch stroker ZR1's that have plenty of torque to get a great launch. I wouldn't bother with those "in between" gears for a stock, or stock displacement ZR1.

This gear question is the most common question for new ZR1 owners. And the biggest reason for that is our varying driving styles. As for myself, I'm always looking for an opportunity to nail it and listen to that great LT5 scream, but that approach is not for everyone.