what gears to go with??

1slosnake

Registered User
Just curious to see what some people are running for gears in their earlier AOD SCs? I was thinking 3:73's but am toying around with 4:10's if I get an art carr tranny. Just want to see what people are going threw the traps at and also at what RPM at the finish and is it in third or fourth? And what gears you are running. So throw in your 2 cents if you could please :cool:

Thanks,
Ross
 
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I'm planning to go with 3.73's in the future - just not sure exactly when. IIRC, 4.10's are a bit much for the AOD and drag racing. I think it was Dave N. who had 4.10's in his SC and was running out of RPM before the traps? And think he's back to 3.73's now.

-Melon
 
Melon said:
I'm planning to go with 3.73's in the future - just not sure exactly when. IIRC, 4.10's are a bit much for the AOD and drag racing. I think it was Dave N. who had 4.10's in his SC and was running out of RPM before the traps? And think he's back to 3.73's now.

-Melon
Good info thanks, Hopefully he will chime in. I want to know exactly what RPM & what gear it is in at the end of the 1/4 mile. 4:10's maybe enough if you have it setup right. But you would have to shift into OD. Which as I said won't be an issue if I decide to go with the art carr tranny. But I would rather see what other people are running first to compare.
 
Melon said:
I'm planning to go with 3.73's in the future - just not sure exactly when. IIRC, 4.10's are a bit much for the AOD and drag racing. I think it was Dave N. who had 4.10's in his SC and was running out of RPM before the traps? And think he's back to 3.73's now.

-Melon

Not exactly. David tried the 4.10's but he didn't like them on the street. I don't believe they made him any slower of faster at the track.

I currently have 3.73's but might go to 3.90's to fully utilize my power range at the track. If I get a taller tire, I might go to 4.10's. But I suspect, I wouldn't light them as much on the street either.

1slosnake said:
Good info thanks, Hopefully he will chime in. I want to know exactly what RPM & what gear it is in at the end of the 1/4 mile. 4:10's maybe enough if you have it setup right. But you would have to shift into OD. Which as I said won't be an issue if I decide to go with the art carr tranny. But I would rather see what other people are running first to compare.

It's not so much that you "have" to shift into OD that should determine your gear selection, it's whether or not you make power over a certain rpm. If your car stops making power at 5000 rpms and 4.10's make you roll through the traps at 6000 rpms, then you would likely benefit from running 3.90's or 3.73's because your power wouldn't be dropping off before the end of the track.
 
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It depends largely on how much slip you have through your torque converter which is a difficult one to pin down.

Theoretically 4.10's would be ideal for most SC's. A mild SC might trap at 95-100mph which would translate to about 5000-5300rpm and a built one might trap at 108-115mph which translates to about 5700-6100rpm. You want to trap about 500rpm above peak HP so that works out about perfect - in theory.

However, you have to consider converter slip. On a 94/95 you'll be trapping with the converter locked so the above numbers hold true, and on a stock 89-93 with direct drive 3rd gear you would also be in good shape. However, anyone with a non-locking converter will have to calculate for converter slip. This will be as little as 5% and perhaps more than 10% depending on stall speed and converter design. I've seen SC converters slip 500rpm in the midrange which is over 10%.

If you have a loose converter you may find that 4.10's are too much gear. I think most of the guys are finding that 3.73's work well. I'd go with 3.73's until you figure out how much power you are going to make and what your actual trap rpms are. Then once you have your combination worked out you can decide if you can afford the extra rpm's that 4.10's will give you. If you can afford the rpms, then the car will be quicker with the 4.10's.

For example, Kurt's car peak's HP at about 5800rpm. For best 1/4 mile times he should be trapping the car about 6300rpm. Currently his car runs about 108mph with 3.73's which is 5200 + converter slip (500rpm?)= 5700. I don't know if this is accurate but if it is then 4.10's would result in 5700 + converter slip (500rpm?) = 6200rpm. I think Kurt's car would be faster with 4.10's. The car will also have less converter flash off the line which should result in better traction too. :)
 
well Dave not to try and steal the thread but what is an ideal rear end gear for 1/4 mile power for a 5 speed??? I don't know if 3.55s are good or if going to a 3.27 would be better I am running BF goodrich KDWs in the rear on 255/60/16s
 
boostedbird said:
well Dave not to try and steal the thread but what is an ideal rear end gear for 1/4 mile power for a 5 speed??? I don't know if 3.55s are good or if going to a 3.27 would be better I am running BF goodrich KDWs in the rear on 255/60/16s


I have 3.27s and they are not good for the strip in a 5 speed, you will probably want 3.08s or 2.73s.
 
doug93sc whats wrong with your 3.27s you don't like .i did a 5 speed swap in my 91 that still has the 3.27's and was thinking about the alum diff and gears.I was wondering like 1slosnake about gears
 
phyxius said:
doug93sc whats wrong with your 3.27s you don't like .i did a 5 speed swap in my 91 that still has the 3.27's and was thinking about the alum diff and gears.I was wondering like 1slosnake about gears

The reason why I don't they are good for the 1/4 is because your shifting into 4th at the end of the track, so when you cross the traps you are at a much lower RPM than the engine should be at. Don't get me wrong I love them for the street!
 
I really want to try 3.08s but i dont know if it would be much of a benefit for the cost. I may just stick with the 2.73s and save up for a cam.
 
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