Can't decide on 3.42 or 3.90. Input appreciated
08-15-2015, 04:35 PM
#1
Staging Lane
Thread Starter
Can't decide on 3.42 or 3.90. Input appreciated My 98 Trans Am is a 2.73 car. It's a turd out of the hole to say the least. I have a set of 3.42's out of an M6. I also have a set of brand new, still in the box Richmond Excel 3.90 gear set. I would like to put the 3.90's in but I think they may be a little too much for highway driving. Seems like with the 3.90's I would barely have a 1st gear but it would damn sure feel good at the drag strip with my 3400 Yank. Future plans are a H/C/I setup btw. So how do 3.90's do on the highway in an A4?
08-15-2015, 07:54 PM
#2
your 2.73s' should be 26-27mpg at freeway legal speeds. My 98 Z28 with 3.23s gave me 24.5 mpg at freeway legal speeds. I ran 4.56s' with an A4 for 4 years, 21.5 mpg, 2500rpm@60mph, 3000rpm@72mph. For most of the time with the 4.56s' I was running a TCI2800, the last 1/2 year with the 4.56s' I ran a Yank SS3600. 4.56s' with any convertor provides a wicked 1st and 2nd gear. I'm currently building a rear with 4.10s' as 4.56s' were too much for the 1/4 but great for the 1/8.
08-16-2015, 04:20 AM
#3
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My 98 Trans Am is a 2.73 car. It's a turd out of the hole to say the least. I have a set of 3.42's out of an M6. I also have a set of brand new, still in the box Richmond Excel 3.90 gear set. I would like to put the 3.90's in but I think they may be a little too much for highway driving. Seems like with the 3.90's I would barely have a 1st gear but it would damn sure feel good at the drag strip with my 3400 Yank. Future plans are a H/C/I setup btw. So how do 3.90's do on the highway in an A4?
Do you already have this "3400" Yank installed? (...and is this a custom unit? I don't recall them having a 3400 off-the-shelf model but perhaps I just forgot.) If so, you won't gain much at the track with a 2.73 to 3.42 swap. Stall speeds of ~3500 and up negate most of the gains from swaps up to about ~3.73. 3.90 might be a bit more noticeable, but I would suggest 4.10 if you're looking for gains. The only thing you'll really get from the 3.42s would be "tighter" feeling around town throttle response, but not much in the way of ET reduction.
08-16-2015, 07:46 PM
#4
Staging Lane
Thread Starter
It shouldn't feel like a turd at all with a 3400-3500 stall, even with 2.73s, unless maybe it's a super low STR converter.
Do you already have this "3400" Yank installed? (...and is this a custom unit? I don't recall them having a 3400 off-the-shelf model but perhaps I just forgot.) If so, you won't gain much at the track with a 2.73 to 3.42 swap. Stall speeds of ~3500 and up negate most of the gains from swaps up to about ~3.73. 3.90 might be a bit more noticeable, but I would suggest 4.10 if you're looking for gains. The only thing you'll really get from the 3.42s would be "tighter" feeling around town throttle response, but not much in the way of ET reduction.
Do you already have this "3400" Yank installed? (...and is this a custom unit? I don't recall them having a 3400 off-the-shelf model but perhaps I just forgot.) If so, you won't gain much at the track with a 2.73 to 3.42 swap. Stall speeds of ~3500 and up negate most of the gains from swaps up to about ~3.73. 3.90 might be a bit more noticeable, but I would suggest 4.10 if you're looking for gains. The only thing you'll really get from the 3.42s would be "tighter" feeling around town throttle response, but not much in the way of ET reduction.
It's not installed yet. It's one of Yanks new power adder series converters.
08-21-2015, 09:03 AM
#5
I have read that 3.42 is the best of both worlds for automatic.
In my personal experience in my A4 with 3.42 I have absolutely great 60 highway roll races. I also have a cool holeshot not like my 3.73 car. Better but not too noticeably better than my 3.23 by much.
With 3.73 roll racing is not good in my own personal experience
3.42 in my opinion the best of both worlds.
Both worlds being a race from a stop and a race from a roll.
Highway driving is comfortable! Would be more so but I need axle bearings
BUT. the corvette ls1 bolt on only fast list consists of mostly 3.73 upwards. I think I saw a single 3.42 on there though. Not 100% though.
In my personal experience in my A4 with 3.42 I have absolutely great 60 highway roll races. I also have a cool holeshot not like my 3.73 car. Better but not too noticeably better than my 3.23 by much.
With 3.73 roll racing is not good in my own personal experience
3.42 in my opinion the best of both worlds.
Both worlds being a race from a stop and a race from a roll.
Highway driving is comfortable! Would be more so but I need axle bearings
BUT. the corvette ls1 bolt on only fast list consists of mostly 3.73 upwards. I think I saw a single 3.42 on there though. Not 100% though.
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08-25-2015, 02:20 PM
#9
Just trying to figure out if its worth swapping out gears? Ive read up on people not really seeing a difference in gear swap. Just wondering if i should keep my 3.23..
I think if i go 3.73 my car would be hard to hook with a 4000 stall on the street...
Just wondering how 3.23 would be on the street and from a roll..
08-25-2015, 03:06 PM
#11
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On the other hand, if you just want to tighten the feel of the converter on the street, then you might find the swap worth it. Some people are more bothered by "looseness" than others, so whether or not this reason is worth it is entirely a matter of personal preference.
08-25-2015, 03:16 PM
#12
08-25-2015, 09:13 PM
#15
I have 3.73's with a FTI-3800 converter and imo it is a great all around gear. The 3.73 helps the converter feel "tighter" and takes less rpm to accelerate... other then that the performance gains are probably minimal with a stall between a 3.23 and 3.73. I am just a hair under 2000rpm @ 60mph. Third gear tops right around 130 @ 6800 rpm with a 26" tire.
08-26-2015, 06:41 AM
#16
Since you're going to use the 4000 with 3.23s'(there's nothing wrong with that combination,I'm currently 3600/3.23s'),definitely install an 'adequately sized' tranny fluid cooler.
Suspension,put in a set of LCA relocation brackets to help reduce 'wheel hop',then decent shocks to help control the suspension from 'loading/unloading' which also contributes to wheel hop,then aftermarket LCAs,then torque arm.
Suspension,put in a set of LCA relocation brackets to help reduce 'wheel hop',then decent shocks to help control the suspension from 'loading/unloading' which also contributes to wheel hop,then aftermarket LCAs,then torque arm.
