bigger gears

[MrCoffee]

ok, I'd like some background info on swaping stock gears with larger ones. I want to know how this helps acceleration. Logic is telling me that it would slow the car down accel wise, but give it a higher top end. I was just need to know the technical reason behind bigger gears. And next issue is, what size gears do i have now, and what size should I look into getting?

[DominusEtDeusNatus]

Numerically higher ratio gears are like using a longer wrench to turn a bolt. It makes it much easier but you'll have to swing in a bigger arc. It's not really how gears work, just an analogy.

[MrCoffee]

i still dont fully understand. I'd think that smaller gears would accel faster. so should you have stock 1st gear, then gradually get bigger. I see how they can improve top speed, so I'd understand replacing 4th gear. And I know you shouldnt have gear sizes too far apart cuz it makes it ahrder to shift. But starting small and gradually getting bigger should be the best way... or am I a complete moron?

[Silver97Camaro]

Well, you have an idea of what gears are about but you are just a little confused. Now a gear that is numerically high such as a 3.73 will have much better acceleration than a gear that is numerically low such as a 3.08 or 2.73. The numerically higher gear allows the engine to move the weight of the car easier that's really all there is to having the proper gear ratio for your car. Now it makes it easier for the engine by allowing the engine to make more revolutions in the same amount of distance covered by the tire. For instance when you ride a 21 speed bicycle when you're going up hill you usually have it in a low gear that makes you pedal really fast. This allows you to be able to get up the hill and not struggle like you would with a bicycle that you can't change the gears on. Now by having a gear that allows you to do that you have in a sense a mechanical advantage. When you are just cruising or are trying to really go fast you put it into a higher gear which slows the rate at which you have to pedal (drops RPM's) to go the same speed. Which allows you to use less energy (or from a cars point of view you'll get better gas mileage). Well, this may be a little confusing to understand with the way I have stated it, but its the best I could do to try and help you understand. If anyone can help my explanation please feel free to add to what I have said. Hope this helps. [img]graemlins/burnout.gif[/img]

[MrCoffee]

no man, your analogy helped alot. I see how it works now. Thanks Silver97Camaro! My next issue is what gears do I have now and what size should I upgrade them to? You used 3.08 and 3.73. Is that what I have and should get? Or was that just hypothetical?

[ May 23, 2002: Message edited by: MrCoffee ]</p>

[Silver97Camaro]

I'm glad I was able to help you out on understanding gears. Well, I'm not really sure what gears you have you'll have to look at your RPO codes to see if you have GU4 which is 3.08 GU5 I believe is 3.23 and GU6 is 3.42. Also do you have an auto or a manual? Another question is how much highway driving do you do and is gas mileage a big thing for you? Then we can decide what gear you should go with. [img]graemlins/burnout.gif[/img]

[MrCoffee]

She's an auto. Where are these codes, on the door? Gas milage doesnt really matter because I've seen it increase so much with the intake thinks I've done. But I dont want it going down drastically, it is a daily driver. I do plan on getting a shift kit and installing it while I'm doing all the tranny work [img]smile.gif[/img]

[Silver97Camaro]

The RPO codes will be on the door. Well, since you have an auto like I do I would bet that you have 3.08's I mean if you didn't get the performance package (Y87) then it's not likely that you have 3.42's. But before you decide on what your going to do find out what gears you have. I mean if you decide that you want 3.42's and you already have 3.42's then it kind of defeats the purpose know what I mean? In that case since you also said that you don't really care about gas mileage but the car is still a daily driver I wouldn't even think about going any higher than 3.73's. Now I have heard many guys say that when they went from 3.08's to 3.42's it's like night and day difference on the acceleration and that that is the way to go. But if you do want the best off the line performance I would go with the 3.73's. But be warned! I have heard many guys say that the performance is great from the 3.73's but it brings your speed limiter down from 118mph to something like 98mph if I remember right. Oh and I'm not sure how you would correct the speedometer and get the shift points right with the 3.73's. With the 3.42's since it was a factory option all you have to do is take your car to someone that is capable of reprograming your ECM with a VIN # from a car that had 3.42's from the factory (don't be scared by the reprograming its much easier than it sounds) and that's it. Speed limiter is corrected, shift points are correct, and gas mileage will be much better for a daily driver than if you run 3.73's. And like I said before don't be afraid of the reprogramming of the ECM. I work at a Chevrolet dealership down here in Florida and have done a job like that before. There really isn't much to it. So if you want my opinion I would say 3.42's are what you want/need. That is if you don't already have them. In fact I plan on putting 3.42's in my car when I do the gear swap. Hope this helps.

Vic Jr. [img]graemlins/burnout.gif[/img]

[ May 23, 2002: Message edited by: Silver97Camaro ]</p>

[MrCoffee]

i didnt know I'd have to reprogram the computer. That can become difficult because I dont know of anyone around here that can do it. Is there any other way around this?

[Silver97Camaro]

Well, to be honest you don't need to have the ECM reprogramed, BUT this will though your speedometer off (not really that bad I mean you just have to find out how much its off and drive accordingly), and since your speedometer is off that will intern though your odometer and trip off. It will also lower your speed limiter like I said before. That's why I recommend having the ECM done. We did a gear switch with my cousins 1992 Camaro and until we got the correct gear for the transmission his speedometer was off by like 5mph. Now since I just stated that we were able to correct my cousin with a gear in the transmission I don't want you to think I was holding out on telling you an easy way of fixing it without reprogramming because it wont work with our cars. He has a 700-R4 Transmission and we have a 4L60-E. They both have the same 1st, 2nd, 3rd, and 4th gear ratios but our transmission is all computer controlled that is why it is necessary to have the ECM reprogramed to correct it. Now there is one alternative MAYBE. I have heard a little talk about a unit called JET SCU (Speed Control Unit) 2000. Here is the LINK for JET SCU2000 info. Now I have no experience with this unit and I do not know anyone who has used it. So I can only tell you what I have heard from guys here at firebirdv6.com and what I have read at the link I just gave to you (after you click on the link scroll all the way to the bottom and you can read about the unit). If you want more information on this unit I would suggest looking in some of the other gear swap topics because I have seen many of the other members talk about it and they may have experience with it. Now you said that it my be hard to have the ECM reprogramed because you don't know anyone who can do it....correct? Well, now I don't know how close you are to a dealership but they can do that for you no problem. Now cost may be another problem. I'm not sure what the hourly rate is where you are at a dealership but to be honest I don't think they would charge you any more than 1.5-2 hours for the job. So that maybe an idea instead of buying the JET SCU2000 which is like $134 if I remember correctly. The only thing I could say is if you have a dealer nearby give them a call and see what they say about having the ECM programed to the new gear ratio. Now you will only be able to go to the dealer for 3.42's because that was a factory option. Like I said all they need to do is get a VIN # from a car equipped with 3.42's and that's it. If you choose to go with 3.73's then that's when you'll have to look into other alternatives or just living with the speedometer being off and all that follows with it. [img]graemlins/burnout.gif[/img]

[ May 23, 2002: Message edited by: Silver97Camaro ]</p>

[Silver97Camaro]

Oh I can't believe I almost forgot! I'm not sure if you already know this, but with all this talk about the ECM and everything I forgot to tell you that if you want to go to a gear ratio that is high than 3.08. You have to get a series 3 carrier. If you have 3.08's (or lower) in your car right now that will have a series 2 carrier and will be an open rear. So you really don't want to reuse your old carrier even if you could. With the open rear you all have the one wheel wonder. Like I said before I'm not sure if you already knew this or not, but I thought I would mention it to you.

[MrCoffee]

geez, thats too much work.. I'll just get a MSD, thanks Silver97Camaro!

[Silver97Camaro]

I'm glad that I was able to help out. Yeah it is a lot of work to get it done correctly. That's why many people just live with the speedometer being off and all that follows. In fact the reason I haven't done a gear swap in my car yet is because of all the work that is needed to do it correctly. I mean I could get used to my speedometer being off. But I couldn't live with my odometer, trip, speed limiter, and shift points being off. I'm just to much of a perfectionist I guess. But at least you know all that the job entails now. So if you choose to do it in the future at least you'll know the correct way to do it and the reason it needs to be done this way. [img]graemlins/burnout.gif[/img]

[ May 24, 2002: Message edited by: Silver97Camaro ]</p>

[cixelsyD21]

Hey, Your info has pretty much convinced me to get 3.42's (i have 3.08 open now.) Where in FL are you at, and how much, an estimation, would the whole entire thing cost?

[strange_trp]

u replacing just the ring/pinion and carrier or do you want to replce entire rear axle assembly (recommended method for beginners)???