M6: 3.42 vs 3.73 differential

[tici]

Last weekend I put a T56 in my originally automatic TA.
The rear end is still a 2.73 and it sucks! (of course).
I'll soon install a shorter ratio but I don't know which one is better.
What are the pro and cons of 3.42 and 3.73 gears?

6th gear manual with 3.73 has the same RPM as the original 4th gear with the A4. Using a 3.42 it will be a little longer: less rpm and a better mileage.

What do you suggest?

Our highways are for 120 - 140 km/h (75 - 87 mph). Is the 3.73 too short?

I saw many M6 peoples installing a shorter gear set as stock. Why?

Thanks - Stefano

[HotRodV6]

Well, most 6 speed cars go with a 4.10 rear gear, it gives great performnance and with the 6th overdrive you can still get some good milage on the freeway. 3.42 wouldnt be much better than what you have now, and since your going to do the swap im would do 3.73 minumim, and best bet would be the 4.10 gears.

Good luck. Wish we had that kind of speedlimit here in the states.

[Hurley711]

I believe the rule of thumb is 4.10 for M6 and 3.73 for A4. I swear I've read that several times before. Get a stall convertor while you're at it.

[GatorSS]

Depends on how much highway driving you're going to do.

[tici]

Highway is 3/4 of what I drive, that's why I was thinking at a low ratio.
the M6 with a 3.73 in 6th gear has the same RPM as the A4 with the 2.73 in 4th, so I won't go higher than that.

[7camaro7]

I have a question, can an LS1 with 3.42 (a4 or m6) be just as good as an LS1 with 4.10(a4 or m6) on acceleration AND top speed?

[sonnyred]

Highway is 3/4 of what I drive, that's why I was thinking at a low ratio.
the M6 with a 3.73 in 6th gear has the same RPM as the A4 with the 2.73 in 4th, so I won't go higher than that.
I always thought 3.73 or 2.73 refered to first gear only and sixth gear was 0.50 on all m6 :think:

[SS#1531]

I'd go for the 3.73's. That's what I have in my M6 car. It's a good compromise. You'll still have great acceleration, and get decent fuel economy. At 85mph I still get about 24mph, or 38.6 kilometres per gallon, which if I did my math right, is 8.77 kilometers per liter.

[sonnyred]

I agree.

[GatorSS]

Since it's 3/4 time highway driving, I'd lean towards the 3.42.

[98_Formula]

definitly 3.73's, i think if u upgraded to the 3.42's you'd just want more and wanna swap out to the 3.73's ne ways. u'll still get good gas milegae, and if u worry bout that just think of me i'm going to putting 4.10's in my A4, ... gas mileage... whats that?

[tici]

we pay now 1.70 - 1.80 swiss francs per liter
about 5.15 - 5.45 US$ per gallon

so mileage DOES count...

[Killer_bluebird]

3.73's Gets's my Vote. I just had them installed on my TA and I was surprise at the difference. During street driving the engine revs a lot quicker the car has more low end, as far as gas milage I rarely bang through all the gears I use 1st, 3rd, 5th on the city with no need to use the other gears, on the Highway I can't remember exactly but the engine still revs less than 2,000rpms at 75mph. As far as the track I don't 1/4 mile my car often (4.10s would be better) but for the road course it is perfect.
My .02

Good Luck.

[GatorSS]

we pay now 1.70 - 1.80 swiss francs per liter
about 5.15 - 5.45 US$ per gallon

so mileage DOES count...
With those prices, 3.42 is looking real sweet!

[7camaro7]

so when you put 3.73's in and take out 3.42's, it affects your overall gas milage? The way I understand it is that those are only the first gear's gears. Why would it have anything to do with gas milage after you shift?

[dubS6]

so when you put 3.73's in and take out 3.42's, it affects your overall gas milage? The way I understand it is that those are only the first gear's gears. Why would it have anything to do with gas milage after you shift?
b/c at 80 mph or so you are at like 2000 rpm w/ 3.42's and with 3.73's you would be at like 70 at 2000 rpm. so at the same rpm or usage of gas you would be going slower with taller gears.

as far as the gears go i would never go below 3.73 with the power you are making. with the supercharger i think 3.73 would be a good gear b/c it holds you in boost longer. I went from 3.42's to 4.10's and only lost about 2 mpg on the highway with my h/c 420hp car. last week i actually got 24 mpg but that was a first. gears make a night and day difference with that much power.

[hammertime]

so when you put 3.73's in and take out 3.42's, it affects your overall gas milage? The way I understand it is that those are only the first gear's gears. Why would it have anything to do with gas milage after you shift?

When you change the rear axle gear, it changes the reduction ratio after the transmission, so all ratios are affected, not just the first gear.

Also, keep in mind - all LS1 era T56's have a .50:1 6th gear. That means your 4.10 gears feel like a 2.05 in 6th.

75 mph w/ 2.73's and .7:1 overdrive = 1875 rpm
75 mph w/ 4.10's and .5:1 overdrive = 2010 rpm

4.10's will give you much improved acceleration out of the hole for a whopping 135 rpm over a 2.73 A4 car.

Go 4.10's!

[hammertime]

TICI - just saw that you are supercharged...

Are you drag racing this car? 1/8 mile, 1/4 mile? What rpm is your peak HP? What is your trap speed? Ideally, you would want your car to just pass peak HP rpm as you run through the timimg traps.

[tici]

TICI - just saw that you are supercharged...

Are you drag racing this car? 1/8 mile, 1/4 mile? What rpm is your peak HP? What is your trap speed? Ideally, you would want your car to just pass peak HP rpm as you run through the timimg traps.

This is a daily drive: 365days a year.
I installed the supercharger because I wasn't happy with the stock power, with the additional 100 RWHP I'm more than happy.
It has a stock behavior under 3000 rpm, then suddendly you feel "a certain difference" ;)
Max torque at 4800 rpm, max power... at 5800 rpm it was still rising but then we stopped logging.
No drag raging. 2-3 spirited trips every year to Germany on the freeways. A couple of races on some rings with friends (Italy, Germany or France).
Normal speed on the highway is 80 mph that's why I was thinking that 3.42 would be a good idea.
I know: for acceleration 3.73 would be better, but the time I spend on racing is 1% of the total driving time so maybe it isn't so impostant to get the maximum out of it.

[GatorSS]

... I know: for acceleration 3.73 would be better, but the time I spend on racing is 1% of the total driving time so maybe it isn't so impostant to get the maximum out of it.
That is the reason I would go with the 3.42.

[Tobynine9]

we pay now 1.70 - 1.80 swiss francs per liter
about 5.15 - 5.45 US$ per gallon

so mileage DOES count...

At least you're driving a cool car in Europe. I didn't see a single American-made car worth talking about during 9 months in France.

[7camaro7]

hahahahaha

[tici]

That is the reason I would go with the 3.42.

:yup:

Right now I still have 2.73 with the M6 and the mileage is worst than with the A4. It's consuming about 10% more fuel as before.

I have a M6 program and the tuning is fine. Timing, fuel... really OK.
Is it possible that with this ratio the engine is working in a sub-optimal RPM range?

I really try to drive in a fuel-saving way but somehow it isn't enough.
The only thing I can imagine it's that I seldom can shift in 6th (it needs at least 65 mph to use it).
In 5th and at the same speed as with the A4 the engine is revving about 7% faster than in overdrive. Is this the cause of more fuel consumption?

[MadSeason]

I believe it's because you're undergeared and using more throttle and fuel to get up to speed. Is your computer also setup for 2.73 gears? It could be making your speed and mileage off

[tici]

Yep, it's set at 2.73.
I really think it's because I too often stay in 5th: I made a long trip on the highway in 6th and the mileage is much better.
Those days I only drive home to office: few miles and low temperatures. This may also cause too much fuel consumption.
It's also possible that because of the 2.73 I'm driving the car in a sub optimal RPM range.
Soon I'll receive a set of 3.42 and see... I'll post the results.

[Silver SS in Germany]

I have 3.42 gears and a 6 speed. I maxed out my speedo at about 5700RPMs in 5th. As long as I'm in Germany I'm going to keep the gears I have. I want 4.10 when I get back to the states and have to worry about speed limits.

[drone14]

The car I bought had a standard diff ratio of 3.46:1 and it wasn't enough. When I went to 3.91 I found I saved fuel because I could drive around the city in 4th and 5th gear a lot.

Lets face it: If you can afford a SUPERCHARGED V8, why are you worrying about fuel economy.

Trade it in on a 4 cylinder something-or-other and your problem is solved.

[tici]

The car I bought had a standard diff ratio of 3.46:1 and it wasn't enough. When I went to 3.91 I found I saved fuel because I could drive around the city in 4th and 5th gear a lot.

Lets face it: If you can afford a SUPERCHARGED V8, why are you worrying about fuel economy.

Trade it in on a 4 cylinder something-or-other and your problem is solved.

One point for you! I know, I shouldn't complain :ughlaugh:

Silver SS in Germany you are about 400 km from here!
Army? School?
Do you have your US car or is it the European version?

[Silver SS in Germany]

One point for you! I know, I shouldn't complain :ughlaugh:

Silver SS in Germany you are about 400 km from here!
Army? School?
Do you have your US car or is it the European version?

I'm in the Army. I have a US spec car. You should drive over here. There are 2 Z28's on this base, and a few other Z's and SS around the Weisbaden area.

[drone14]

Tici,

I didn't mean to shoot you down at all, but in Australia we wouldn't ask that question because we would be laughed out of the forum.

I don't know how fuel prices compare in Europe but I'm sure everyone is suffering from high prices.

I think if you go 3.73 or higher you won't regret it.

cheers,

drone14

[tici]

I'm in the Army. I have a US spec car. You should drive over here. There are 2 Z28's on this base, and a few other Z's and SS around the Weisbaden area.

OK if it was in summer, but with the actual wheater... how long will you stay?


drone 14 5.15 - 5.45 US$ per gallon.
If I would use this car only during the weekend It wouldn't be a problem, but it's my daily drive and I almost cry every time I go to the gas station... $80 to fill the tank!
About once a week... :(

[drone14]

That is a pretty high price!! I knew that Europe was suffering a lot more than us and the US but I didn't know that it was that high.

I think 3.73 is a perfect match for the M6 in any fuel situation.

SILVER SS: In Australia the army bases are prime areas for people to steal cars. How is it in Europe?

[Silver SS in Germany]

I haven't heard of anyone getting a car stolen since I've been here.

[dubS6]

SILVER SS: In Australia the army bases are prime areas for people to steal cars. How is it in Europe?
i would never steal a car from a place where people sleep next to there guns.

[Silver SS in Germany]

Yeah but all of the guns are locked up. It would probably take about 10 minutes before we could get to them. If you don't have proper I.D. Then you are not getting on base.

[drone14]

I think the bases in Australia don't have the carpark security that exists over there, but that still doesn't explain why so many get taken.

I would say that a lot of them are "inside jobs" to some degree.

[Chevypowr]

When you change the rear axle gear, it changes the reduction ratio after the transmission, so all ratios are affected, not just the first gear.

Also, keep in mind - all LS1 era T56's have a .50:1 6th gear. That means your 4.10 gears feel like a 2.05 in 6th.

75 mph w/ 2.73's and .7:1 overdrive = 1875 rpm
75 mph w/ 4.10's and .5:1 overdrive = 2010 rpm

4.10's will give you much improved acceleration out of the hole for a whopping 135 rpm over a 2.73 A4 car.

Go 4.10's!
I do 70mph at 1500RPM with 3.42 M6. I have a richmond 3.73 set waiting to be installed. can't wait.

I shift out of 5th gear at 6000rpms at 140mph drops to like 3500rpms in 6th (about don't quote me, i try to keep my eyes on the road:zoom: )

[Chevypowr]

Oh and what posi traction dif should i go with? I have the stock auburn but its going, and i'm looking to upgrade.

[Silver SS in Germany]

I do 70mph at 1500RPM with 3.42 M6. I have a richmond 3.73 set waiting to be installed. can't wait.

I shift out of 5th gear at 6000rpms at 140mph drops to like 3500rpms in 6th (about don't quote me, i try to keep my eyes on the road:zoom: )

How are you maxing 5th gear at 140mph? We have the same trans and rear gear? I have never seen 6000 RPM in 5th.

[tici]

6000 rpm in 5th is about 180 mph...
I feel my convertible falling apart at 150 mph!

Silver SS: how long will you stay in Germany? Sorry but I don't know how your army stuff works... are you all professional? Is it like a job with a contract? Can you choose to go somewhere like in Germany or they just send you where they need troups?

[Silver SS in Germany]

I will be here til July 2007. It depends on what job you have, to where they send you. Like for my job I can only go to 3 places in Germany. I have about 20 more months left in the Army til I can retire. I'm thinking of re-enlisting for 2 more. Then I will have 22 years in. It will give me a better chance of getting promoted and a bigger retirement pay.

[Chevypowr]

I have the 6 speed T56 tranny. 5th goes to about 130-140mph, then i still have 6th but the gearing is too low to accel any further than 145mph due to wind resistance and such.
- how so i get to 140, find an open highway and hope there's no cops.

[Silver SS in Germany]

I have the 6 speed T56 tranny. 5th goes to about 130-140mph, then i still have 6th but the gearing is too low to accel any further than 145mph due to wind resistance and such.
- how so i get to 140, find an open highway and hope there's no cops.

I mean that we have the same trans(T56) and rear gears(3.42) right? Or do we?

[Chevypowr]

I mean that we have the same trans(T56) and rear gears(3.42) right? Or do we?
yeah i believe so, i have the T56 3.42 combo

[7camaro7]

I personally don't see anything wrong with 3.42's on the street as far as gas milage and performance go... both are good with this set up, I think....:approved:

[Chevypowr]

I personally don't see anything wrong with 3.42's on the street as far as gas milage and performance go... both are good with this set up, I think....:approved: I am happy with the stock 3.42 except when i'm going highway speeds above 125mph then the car doesn't climb as easily due to wind resistance and the low gearing of 6th. I'm looking forward to installing the 3.73 for that reason. Then the engine won't have to work as hard, and should climb up in the rpms much easier at the higher speeds. Not to mention how much quicker bottom end will be. I originally was going to go with 4.10 but figured they had to be a bit too high of a gear ration for daily street use. :think:

[tici]

There are gear kits to make 5th and 6th shorter, it may help for high speed

[Chevypowr]

Were can I check these gear kits out at? Do you have a website, that might be something to consider.

[7camaro7]

I'm so confused :haha: So if you get taller gears like 3.73, you'll have more acceleration on the bottom end AND top? I thought it would be more like one or the other.

[Chevypowr]

I'm so confused :haha: So if you get taller gears like 3.73, you'll have more acceleration on the bottom end AND top? I thought it would be more like one or the other.

it will shorten the length of each gear, therefore bringing your top end down, but since the t56 already is capable of reaching speeds of 160mph+ te top end would be brought down to let say 150mph (just an ex.) So your engine will be able to rev easier to 150 then 160 because a higher gear ratio makes it easier for your engine to work. So you would run throught the bottom end gears much quicker and accelerate much faster to 150mph then try to accelerate to 160 which is harder for it to achieve. This is sort of difficult to explain but in turn, 3.73 would make your car faster all around. If you would go to 4.10's it would be even quicker but top end might be limited to 140MPH and now your are losing top end, but gaining qucker bottom end times which would be better for 1/4 mile runs where you don't see speed of 140mph anyway, so the extra top end isnt needed.

[Silver SS in Germany]

Dude just go to www.f-body.org/gears/ Check your info. You might have different gears. This does not factor in wind resistance.

[Silver SS in Germany]

RPM 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear
500 4 6 9 11 15 22
600 5 8 10 13 18 27
700 6 9 12 16 21 31
800 7 10 14 18 23 36
900 8 11 15 20 26 40
1000 8 13 17 22 29 45
1100 9 14 19 25 32 49
1200 10 15 21 27 35 54
1300 11 16 22 29 38 58
1400 12 18 24 31 41 63
1500 13 19 26 33 44 67
1600 13 20 27 36 47 71
1700 14 21 29 38 50 76
1800 15 23 31 40 53 80
1900 16 24 33 42 56 85
2000 17 25 34 45 59 89
2100 18 26 36 47 62 94
2200 18 28 38 49 65 98
2300 19 29 39 51 68 103
2400 20 30 41 54 70 107
2500 21 31 43 56 73 112
2600 22 33 45 58 76 116
2700 23 34 46 60 79 121
2800 23 35 48 63 82 125
2900 24 36 50 65 85 129
3000 25 38 52 67 88 134
3100 26 39 53 69 91 138
3200 27 40 55 71 94 143
3300 28 41 57 74 97 147
3400 29 43 58 76 100 152
3500 29 44 60 78 103 156
3600 30 45 62 80 106 161
3700 31 46 64 83 109 165
3800 32 48 65 85 112 170
3900 33 49 67 87 115 174
4000 34 50 69 89 117 179
4100 34 51 70 92 120 183
4200 35 53 72 94 123 188
4300 36 54 74 96 126 192
4400 37 55 76 98 129 196
4500 38 56 77 100 132 201
4600 39 58 79 103 135 205
4700 39 59 81 105 138 210
4800 40 60 82 107 141 214
4900 41 61 84 109 144 219
5000 42 63 86 112 147 223
5100 43 64 88 114 150 228
5200 44 65 89 116 153 232
5300 44 66 91 118 156 237
5400 45 68 93 121 159 241
5500 46 69 94 123 162 246
5600 47 70 96 125 164 250
5800 49 73 100 129 170 259
5900 50 74 101 132 173 263
6000 50 75 103 134 176 268
6100 51 76 105 136 179 272
6200 52 78 106 138 182 277
6300 53 79 108 141 185 281
6400 54 80 110 143 188 286
6500 55 82 112 145 191 290
6600 55 83 113 147 194 295
6700 56 84 115 150 197 299
6800 57 85 117 152 200 304

So if I could redline my car in 6th gear I could go 304mph.

[tici]

Were can I check these gear kits out at? Do you have a website, that might be something to consider.

sorry I don't know where to get them.
I only know they have 5th 0.82 (original 0.74) and 6th 0.73 (original 0.50)
Maybe here http://www.richmondgear.com/

[Chevypowr]

RPM 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear
500 4 6 9 11 15 22
600 5 8 10 13 18 27
700 6 9 12 16 21 31
800 7 10 14 18 23 36
900 8 11 15 20 26 40
1000 8 13 17 22 29 45
1100 9 14 19 25 32 49
1200 10 15 21 27 35 54
1300 11 16 22 29 38 58
1400 12 18 24 31 41 63
1500 13 19 26 33 44 67
1600 13 20 27 36 47 71
1700 14 21 29 38 50 76
1800 15 23 31 40 53 80
1900 16 24 33 42 56 85
2000 17 25 34 45 59 89
2100 18 26 36 47 62 94
2200 18 28 38 49 65 98
2300 19 29 39 51 68 103
2400 20 30 41 54 70 107
2500 21 31 43 56 73 112
2600 22 33 45 58 76 116
2700 23 34 46 60 79 121
2800 23 35 48 63 82 125
2900 24 36 50 65 85 129
3000 25 38 52 67 88 134
3100 26 39 53 69 91 138
3200 27 40 55 71 94 143
3300 28 41 57 74 97 147
3400 29 43 58 76 100 152
3500 29 44 60 78 103 156
3600 30 45 62 80 106 161
3700 31 46 64 83 109 165
3800 32 48 65 85 112 170
3900 33 49 67 87 115 174
4000 34 50 69 89 117 179
4100 34 51 70 92 120 183
4200 35 53 72 94 123 188
4300 36 54 74 96 126 192
4400 37 55 76 98 129 196
4500 38 56 77 100 132 201
4600 39 58 79 103 135 205
4700 39 59 81 105 138 210
4800 40 60 82 107 141 214
4900 41 61 84 109 144 219
5000 42 63 86 112 147 223
5100 43 64 88 114 150 228
5200 44 65 89 116 153 232
5300 44 66 91 118 156 237
5400 45 68 93 121 159 241
5500 46 69 94 123 162 246
5600 47 70 96 125 164 250
5700 48 71 98 127 167 254
5800 49 73 100 129 170 259
5900 50 74 101 132 173 263
6000 50 75 103 134 176 268
6100 51 76 105 136 179 272
6200 52 78 106 138 182 277
6300 53 79 108 141 185 281
6400 54 80 110 143 188 286
6500 55 82 112 145 191 290
6600 55 83 113 147 194 295
6700 56 84 115 150 197 299
6800 57 85 117 152 200 304

So if I could redline my car in 6th gear I could go 304mph.

Oh man imagine that. I took my camaro to 140 once and in 6th I was in between 3500-4500 but I was watching the road so I don't know exactly. I think that chart is a bit top-heavy. Or it doesn't simulate real driving conditions like wind resistance, dead weight of the vehicle and such

[Silver SS in Germany]

Someone else posted gear ratios a while back and I wrote them down.
1 2.66
2 1.78
3 1.30
4 1.0
5 .75
6 .50

[BIG D's SS]

I have 4.10's in my SS and at 75 I'm turning about 2000 80 is about 2200.

[Chevypowr]

I have 4.10's in my SS and at 75 I'm turning about 2000 80 is about 2200.

Thats not as bad as I thought it would be, with my stock 3.42 i'm turning 1500 at 70. What MPH does first gear redline at?

[rlerma]

All this information is very interesting, i just got a 2000 Camaro SS with 65,000 mlies. I am more interested in highway racing. I was testing it and went 155MPH, but how much faster can you go on an LS1? I know the suspension has to be upgrated, any tips? i am new at this...

[MadSeason]

All this information is very interesting, i just got a 2000 Camaro SS with 65,000 mlies. I am more interested in highway racing. I was testing it and went 155MPH, but how much faster can you go on an LS1? I know the suspension has to be upgrated, any tips? i am new at this...

http://www.gmhightechperformance.com/features/0503htp_speed/ should interest you