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Post by tachout on Jul 7, 2008 14:51:01 GMT -7
Well I just looked up the code that say what my rear gears that came in my car are. It says they are a set of 3.07 rear gears. Is that cool for the racing I have started doing in this thing? I really do not want to change them if it will not hurt anything running them on the Drag Strip. Right now I need to work more on consistancy that speed so If I will not break them running them hard, I will not change them. I do know that it has been sugested that I change my rear gears, as that would be one of the first things I should change when racing, but not sure if it is just to make it run faster 1/4 mile times, or for some other reason.
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Post by highpockets on Jul 7, 2008 15:57:32 GMT -7
I am sure one of the C4 gurus will jump in pretty quick,but lets see if I remember my stuff correct. As it sits,car should have a D36 which is the weaker rear diff,Man trans cars at least the older ones were D44 which is a heavier duty setup. As for performance,you would probably see some with a gear swap,however, I would be looking for a D44 setup for yours with gearing closer to what you want to end up with. I am pretty sure if you get batwing and all it bolts in,seems like driveshaft is shorter on the D44 due to larger pinion/longer yoke.Anyway,I know they will chime in shortly,I think for the dollars that would probably be your best bet.
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Post by tachout on Jul 7, 2008 15:59:14 GMT -7
Thanks, I can always count on your experience and expertise.
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Post by Crossfire84 on Jul 7, 2008 18:42:20 GMT -7
It all depends on what you value most. For the quickest ETs, you should reach your ideal shift rpms, just past the finish line, in third gear in your automatic. That would take gears pretty close to the popular 3.54:1 ratio. It is an after market, only, ratio. Although the D44 was made with 3.54s, the D36 was not. Many of the newer C4s autos came with 2 series ratios, some as high as 2.59:1. Guys with these cars covet the 3.07 diff you presently have.
All C4 autos came with the D36. In 1985 through 1996, all but the '84, the manual trans cars came with the stronger D44 diff. With the power you are currently developing, your D36 will live a long happy life. Mine has approx 800 passes on it and shows no signs of problems. The D36 is actually stronger with the 3.07 gears than it would be with a lower ratio. However, until you make some more HP, I don't think diff strength is going to be an issue.
The D44 batwing is different than the D36 where it bolts to the differential. They both mount into the car exactly the same. Typically, a "conversion" includes the diff with batwing, the "C" beam and the drive shaft. Because of the difference in the gear size (7.875" for the D36 vs 8.5" for the D44) the pinion yoke on the D44 is located 13/16" farther forward than on the D36. They both take a Spicer 1310 series u joint. Because the diff is mounted to the chassis and the "C" beam prevents relative movement, the amount of slip necessary at the slip yoke is nil. Several people I know have used the existing, longer, auto trans, drive shaft in a D36 to D44 conversion with no problems. Holes can be drilled onto the "C" beam so it will fit, also. Therefore, all you NEED is the diff with batwing
A gear change is global. No matter what, your engine will turn higher rpms under any given set of conditions with lower gears. That can make the car more responsive and more fun to drive under any conditions. The draw back is that, no matter what, your engine will turn higher rpms under any given set of conditions. That can make extended high speed cruising less enjoyable. And especially on the road, the fuel mileage is likely to suffer.
On the other hand, a higher stall torque converter will do more for your 1/4 mile ETs than gears. However, the converter is only really noticeable coming out of the hole. It doesn't give the constant advantage, at all speeds, gears do. On the highway, once the converter is locked up, the cruise rpms and gas mileage remain unchanged.
Gears cost approx $250.00 to $300.00. A bearing kit a hundred or so. You can R&R the diff yourself, so all you have to add is the labor of a friendly gear man and some incidentials like gear grease and posi additive, etc. $500 to $600.00 should do it, unless you go used.
A D44 conversion is starting to get expensive. I have seen Corvette specialists selling conversions on eBay for up wards of $2500.00, used. Anything under $1000.00 is a bargain if it doesn't need repairs. Like the D36 gear change, you can do the R&R.
A converter can cost between $300.00 and $1000.00. You can probably do that yourself, too.
There are some pros and cons, plus some details to consider while contemplating a gear change. Have fun.
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