3.73 in A4 LS1 Trans Am
03-03-2016, 03:23 PM
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3.73 in A4 LS1 Trans Am Hey everyone, I have an A4 Trans Am it has Longtube Headers, and a Borla adj catback exhuast. I wanted to know if I were to put in 3.73 gears in the 10 bolt how well would it hold up? Should I just save up the $2k for a Moser 9'? I don't plan on doing much engine mods in the near future so I just wanted to know if the 10 bolt would hold for now
03-03-2016, 09:15 PM
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03-03-2016, 10:11 PM
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Also something to look at during your gear swap cause I'm actually getting it done next week where I work. Some may say it does not matter. However if you have bolt ons and a tune like myself it would be extra insurance to get what I got for my 10 bolt.
1. BMR torque arm (irrelevant to the topic but I got to finish my suspension figured I'd share)
2. Name brand gears, I went with Motive
3. Motive install kit with the Timken bearings
4. Axle tube bearings and seals
5. Option of course solid pinion spacer, I got one though
6. To some may not help but for $35 your in there TA stud kit
7. Axle housing girdle.
1. BMR torque arm (irrelevant to the topic but I got to finish my suspension figured I'd share)
2. Name brand gears, I went with Motive
3. Motive install kit with the Timken bearings
4. Axle tube bearings and seals
5. Option of course solid pinion spacer, I got one though
6. To some may not help but for $35 your in there TA stud kit
7. Axle housing girdle.
03-04-2016, 01:51 AM
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I would not even consider a gear swap on an A4 LS1 car until after the torque converter has been optimized (~3500ish for a stock/mild engine, more for heads/cam setups.)
If you happen to have 3.23s (GU5) already in place, then the 3.73 swap is even less beneficial. Gears swaps from 2.73/3.23 to 3.73 offer much bigger gains in applications that don't have an optimized stall speed. But with a 3500+ stall speed, regardless of your stock gear ratio (2.73 or 3.23), there won't be much more to gain in terms of acceleration performance from a 3.73 swap.
I wouldn't spend the money for a 9" in an automatic application that's mostly stock and street driven. The 7.5" can live a long life in such a setting.
If you happen to have 3.23s (GU5) already in place, then the 3.73 swap is even less beneficial. Gears swaps from 2.73/3.23 to 3.73 offer much bigger gains in applications that don't have an optimized stall speed. But with a 3500+ stall speed, regardless of your stock gear ratio (2.73 or 3.23), there won't be much more to gain in terms of acceleration performance from a 3.73 swap.
I wouldn't spend the money for a 9" in an automatic application that's mostly stock and street driven. The 7.5" can live a long life in such a setting.
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03-04-2016, 05:58 AM
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Also something to look at during your gear swap cause I'm actually getting it done next week where I work. Some may say it does not matter. However if you have bolt ons and a tune like myself it would be extra insurance to get what I got for my 10 bolt.
1. BMR torque arm (irrelevant to the topic but I got to finish my suspension figured I'd share)
2. Name brand gears, I went with Motive
3. Motive install kit with the Timken bearings
4. Axle tube bearings and seals
5. Option of course solid pinion spacer, I got one though
6. To some may not help but for $35 your in there TA stud kit
7. Axle housing girdle.
1. BMR torque arm (irrelevant to the topic but I got to finish my suspension figured I'd share)
2. Name brand gears, I went with Motive
3. Motive install kit with the Timken bearings
4. Axle tube bearings and seals
5. Option of course solid pinion spacer, I got one though
6. To some may not help but for $35 your in there TA stud kit
7. Axle housing girdle.
03-04-2016, 06:00 AM
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I would not even consider a gear swap on an A4 LS1 car until after the torque converter has been optimized (~3500ish for a stock/mild engine, more for heads/cam setups.)
If you happen to have 3.23s (GU5) already in place, then the 3.73 swap is even less beneficial. Gears swaps from 2.73/3.23 to 3.73 offer much bigger gains in applications that don't have an optimized stall speed. But with a 3500+ stall speed, regardless of your stock gear ratio (2.73 or 3.23), there won't be much more to gain in terms of acceleration performance from a 3.73 swap.
I wouldn't spend the money for a 9" in an automatic application that's mostly stock and street driven. The 7.5" can live a long life in such a setting.
If you happen to have 3.23s (GU5) already in place, then the 3.73 swap is even less beneficial. Gears swaps from 2.73/3.23 to 3.73 offer much bigger gains in applications that don't have an optimized stall speed. But with a 3500+ stall speed, regardless of your stock gear ratio (2.73 or 3.23), there won't be much more to gain in terms of acceleration performance from a 3.73 swap.
I wouldn't spend the money for a 9" in an automatic application that's mostly stock and street driven. The 7.5" can live a long life in such a setting.
Last edited by Charles Garcia; 03-04-2016 at 06:11 AM.
03-04-2016, 12:38 PM
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I'd recommend changing the stall speed first then. The gains from a 3500+ stall speed will be about twice what you'd gain from a 3.73 swap, and at a similar cost. Once the stall is done any additional gains from the gears would be marginal, though they do make the car feel quicker than it is.
03-05-2016, 08:49 AM
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A stalled car with 2.73s is faster then a stock stall 3.73 car is what rpm is saying. Stall is the best bang for the buck. However that doesnt mean gear swaps arent worth it. I just pulled my 3.73s to install 4.10s to optimize my combo for the 1/4 mile.
03-05-2016, 10:35 AM
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With a 3500+ stall speed in place, a 2.73 or 3.23 to 3.73 swap isn't worth more than about 0.10-0.15 seconds of ET reduction. Not really enough gain to justify the cost, unless you can do the install yourself (I know YOU can 
), or you're looking for every last tenth of ET, or you're one of the few who is particularly bothered by part throttle looseness (shouldn't be much of an issue with a top shelf converter.)
), or you're looking for every last tenth of ET, or you're one of the few who is particularly bothered by part throttle looseness (shouldn't be much of an issue with a top shelf converter.)
03-05-2016, 11:37 AM
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With a 3500+ stall speed in place, a 2.73 or 3.23 to 3.73 swap isn't worth more than about 0.10-0.15 seconds of ET reduction. Not really enough gain to justify the cost, unless you can do the install yourself (I know you can ), or you're looking for every last tenth of ET, or you're one of the few who is particularly bothered by part throttle looseness (shouldn't be much of an issue with a top shelf converter.)
), or you're looking for every last tenth of ET, or you're one of the few who is particularly bothered by part throttle looseness (shouldn't be much of an issue with a top shelf converter.)