New Gearbox Ratios
Discussion
Hi All
I hope to change my gearbox over the winter and wonder what you all think of the gear ratios I'm thinking of fitting. My Procharged Chevy will have the rev limiter set at 6,500rpm. So here are the ratios and speeds at 6,500rpm. Sixth gear is extra tall for cruising giving only 2,050rpm at 70mph.
1st 3.81 38mph
2nd 2.04 71mph
3rd 1.40 103mph
4th 1.11 130mph
5th 0.91 158mph
6th 0.65 221mph
Final drive 3.44
I have a complete free choice of gear ratios and final drive ratios within reason. All the gears will be custom made. All suggestions and thoughts welcome.
Regards Dave
I hope to change my gearbox over the winter and wonder what you all think of the gear ratios I'm thinking of fitting. My Procharged Chevy will have the rev limiter set at 6,500rpm. So here are the ratios and speeds at 6,500rpm. Sixth gear is extra tall for cruising giving only 2,050rpm at 70mph.
1st 3.81 38mph
2nd 2.04 71mph
3rd 1.40 103mph
4th 1.11 130mph
5th 0.91 158mph
6th 0.65 221mph
Final drive 3.44
I have a complete free choice of gear ratios and final drive ratios within reason. All the gears will be custom made. All suggestions and thoughts welcome.
Regards Dave
Watcha Dave,
As you know, the GTW has 650bhp and the gear set that PH II supplied for me is bang on, I do have my rev limit set @ 7,200rpm but I still think they may be worth consideration, they are as follows:
1st;2.716=74.1mph
2nd;1.579=102.1mph
3rd;1.174=137.3mph
4th;0.923=174.6mph
5th;0.756=213.2mph
I was a little concerned in the beginning that maybe first gear was a little to steep but in reality, it is not an issue. Although my motor is a 434 torque monster, I think yours may be more tractable from rest making a longer first even more appealing.
Another theory that I stand by is that you do not need a six speed gearbox with a stout SBC, it is a waste of time and is also a weaker gearbox. I understand the cruise gear theory but come on, honestly, these cars are not for cruising and even so, especially in your case, you will see pretty good economy of boost ( as much as you might ever see on a SBC in any case ) and I for one would be far more inclined to 'tune' the box to release the full potential of that stonking motor of yours
As you know, the GTW has 650bhp and the gear set that PH II supplied for me is bang on, I do have my rev limit set @ 7,200rpm but I still think they may be worth consideration, they are as follows:
1st;2.716=74.1mph
2nd;1.579=102.1mph
3rd;1.174=137.3mph
4th;0.923=174.6mph
5th;0.756=213.2mph
I was a little concerned in the beginning that maybe first gear was a little to steep but in reality, it is not an issue. Although my motor is a 434 torque monster, I think yours may be more tractable from rest making a longer first even more appealing.
Another theory that I stand by is that you do not need a six speed gearbox with a stout SBC, it is a waste of time and is also a weaker gearbox. I understand the cruise gear theory but come on, honestly, these cars are not for cruising and even so, especially in your case, you will see pretty good economy of boost ( as much as you might ever see on a SBC in any case ) and I for one would be far more inclined to 'tune' the box to release the full potential of that stonking motor of yours
Hi Wayne
Thanks for your gear info. Like you say I would have been a bit worried about such a tall first gear, but if you say it works then this is the kind of information I need to make my final decision. I understand what your saying about not needing a sixth gear but the box I'm going to fit only comes as a six speed. I am looking forward to a few trips to Europe next year so I'll save sixth for that kind of journey. Like you say, I do want to tune the gearbox to get the best out of my engine.
Regards Dave
Thanks for your gear info. Like you say I would have been a bit worried about such a tall first gear, but if you say it works then this is the kind of information I need to make my final decision. I understand what your saying about not needing a sixth gear but the box I'm going to fit only comes as a six speed. I am looking forward to a few trips to Europe next year so I'll save sixth for that kind of journey. Like you say, I do want to tune the gearbox to get the best out of my engine.
Regards Dave
Only my closest hombres know what I'm planning. Keep it under your hat. I will tell all in the spring. If it all works!CanAm Dave said:
Is anyone else using different ratios or could you tell me what ratios you are using and what you think of them.
Regards Dave
I am. Can remember which though. (I'm sure there is a thread about it though). I'm probably want to put mine back to somewhere near std over the winter. So they could be available to swap with someone or at a special price.Regards Dave
Pete
JOHN-ULTIMA said:
HI canam dave my personal oppion on your ratio choice would have been:
1st 3.167:1 2nd 2.176:1 3rd 1.5:1 4th 1.130:1 5th 0.867:1 6th 0.679:1
with final drive ratio of 3.444:1
cheers
john
Thanks John, Just put those into my gearcalc and they look very good.1st 3.167:1 2nd 2.176:1 3rd 1.5:1 4th 1.130:1 5th 0.867:1 6th 0.679:1
with final drive ratio of 3.444:1
cheers
john
Speeds at 6500rpm
1st 46mph
2nd 67mph
3rd 97mph
4th 129mph
5th 168mph
6th 214mph
Regards Dave
GTWayne said:
Watcha Dave,
As you know, the GTW has 650bhp and the gear set that PH II supplied for me is bang on, I do have my rev limit set @ 7,200rpm but I still think they may be worth consideration, they are as follows:
1st;2.716=74.1mph
2nd;1.579=102.1mph
3rd;1.174=137.3mph
4th;0.923=174.6mph
5th;0.756=213.2mph
I was a little concerned in the beginning that maybe first gear was a little to steep but in reality, it is not an issue. Although my motor is a 434 torque monster, I think yours may be more tractable from rest making a longer first even more appealing.
Another theory that I stand by is that you do not need a six speed gearbox with a stout SBC, it is a waste of time and is also a weaker gearbox. I understand the cruise gear theory but come on, honestly, these cars are not for cruising and even so, especially in your case, you will see pretty good economy of boost ( as much as you might ever see on a SBC in any case ) and I for one would be far more inclined to 'tune' the box to release the full potential of that stonking motor of yours
Hi Wayne As you know, the GTW has 650bhp and the gear set that PH II supplied for me is bang on, I do have my rev limit set @ 7,200rpm but I still think they may be worth consideration, they are as follows:
1st;2.716=74.1mph
2nd;1.579=102.1mph
3rd;1.174=137.3mph
4th;0.923=174.6mph
5th;0.756=213.2mph
I was a little concerned in the beginning that maybe first gear was a little to steep but in reality, it is not an issue. Although my motor is a 434 torque monster, I think yours may be more tractable from rest making a longer first even more appealing.
Another theory that I stand by is that you do not need a six speed gearbox with a stout SBC, it is a waste of time and is also a weaker gearbox. I understand the cruise gear theory but come on, honestly, these cars are not for cruising and even so, especially in your case, you will see pretty good economy of boost ( as much as you might ever see on a SBC in any case ) and I for one would be far more inclined to 'tune' the box to release the full potential of that stonking motor of yours
If you get the chance can you check your 1st gear ratio as it only works out to 59mph in my gearcalc.
Regards Dave
Seeing as you are looking for peoples view I thought I'd dropped your rpm and wheel size in my spreadsheet and I'd use the below gears as a minimum.
gear ratio speed rpm drop on change
1st 2.333 62mph
2nd 1.500 96mph 2735rpm
3rd 1.173 123mph 1417rpm
4th 0.966 149mph 1147rpm
5th 0.814 177mph 1023rpm
6th 0.650 221mph 1310rpm
On my canam I had wide gears (as it was a 4 speed with a 212mph top gear) and up to 150mph it was devastating (which was up to 3rd gear) and only changing into top gear could it have done with closer together gears.
As an example my car had a mear approx 500bhp & same torque and I geniunelly think it would have been slower to 150mph if the ratios were closer together, so yours will be even more devastating with the same ratios. Mine were:
1st 59mph
2nd 97mph 2722rpm
3rd 148mph 2418rpm
4th 212mph 2100rpm
For My GTT I am limited by cash so I won't be specifying all my ratios so it will be a compramise of the best ratios for the GT3 race box and the GT2 box's that I have, however I will be buying a new 6th similar to the one above and with 6500rpm and my wheels will give a 246mph top gear purelly for motorway cruising as like Wayne I think 6 speeds is really overkill for our lightweight torque monsters..... and my 5th will still get me to over 190mph, more than enough for any track.
gear ratio speed rpm drop on change
1st 2.333 62mph
2nd 1.500 96mph 2735rpm
3rd 1.173 123mph 1417rpm
4th 0.966 149mph 1147rpm
5th 0.814 177mph 1023rpm
6th 0.650 221mph 1310rpm
On my canam I had wide gears (as it was a 4 speed with a 212mph top gear) and up to 150mph it was devastating (which was up to 3rd gear) and only changing into top gear could it have done with closer together gears.
As an example my car had a mear approx 500bhp & same torque and I geniunelly think it would have been slower to 150mph if the ratios were closer together, so yours will be even more devastating with the same ratios. Mine were:
1st 59mph
2nd 97mph 2722rpm
3rd 148mph 2418rpm
4th 212mph 2100rpm
For My GTT I am limited by cash so I won't be specifying all my ratios so it will be a compramise of the best ratios for the GT3 race box and the GT2 box's that I have, however I will be buying a new 6th similar to the one above and with 6500rpm and my wheels will give a 246mph top gear purelly for motorway cruising as like Wayne I think 6 speeds is really overkill for our lightweight torque monsters..... and my 5th will still get me to over 190mph, more than enough for any track.
CanAm Dave said:
GTWayne said:
Watcha Dave,
As you know, the GTW has 650bhp and the gear set that PH II supplied for me is bang on, I do have my rev limit set @ 7,200rpm but I still think they may be worth consideration, they are as follows:
1st;2.716=74.1mph
2nd;1.579=102.1mph
3rd;1.174=137.3mph
4th;0.923=174.6mph
5th;0.756=213.2mph
I was a little concerned in the beginning that maybe first gear was a little to steep but in reality, it is not an issue. Although my motor is a 434 torque monster, I think yours may be more tractable from rest making a longer first even more appealing.
Another theory that I stand by is that you do not need a six speed gearbox with a stout SBC, it is a waste of time and is also a weaker gearbox. I understand the cruise gear theory but come on, honestly, these cars are not for cruising and even so, especially in your case, you will see pretty good economy of boost ( as much as you might ever see on a SBC in any case ) and I for one would be far more inclined to 'tune' the box to release the full potential of that stonking motor of yours
Hi Wayne As you know, the GTW has 650bhp and the gear set that PH II supplied for me is bang on, I do have my rev limit set @ 7,200rpm but I still think they may be worth consideration, they are as follows:
1st;2.716=74.1mph
2nd;1.579=102.1mph
3rd;1.174=137.3mph
4th;0.923=174.6mph
5th;0.756=213.2mph
I was a little concerned in the beginning that maybe first gear was a little to steep but in reality, it is not an issue. Although my motor is a 434 torque monster, I think yours may be more tractable from rest making a longer first even more appealing.
Another theory that I stand by is that you do not need a six speed gearbox with a stout SBC, it is a waste of time and is also a weaker gearbox. I understand the cruise gear theory but come on, honestly, these cars are not for cruising and even so, especially in your case, you will see pretty good economy of boost ( as much as you might ever see on a SBC in any case ) and I for one would be far more inclined to 'tune' the box to release the full potential of that stonking motor of yours
If you get the chance can you check your 1st gear ratio as it only works out to 59mph in my gearcalc.
Regards Dave
GTWayne said:
Hello Dave, checked and figures are as follows;
1st: 2.176 ( 17,37 ) overall ratio 7.494 with 3.444 ( 09,32 ) diff ratio, hope this helps. I do not think the actual gear is incorrect in the car as it defo makes 70 in first but maybe the calc sheet I have here is wrong?
Cheers Wayne 1st: 2.176 ( 17,37 ) overall ratio 7.494 with 3.444 ( 09,32 ) diff ratio, hope this helps. I do not think the actual gear is incorrect in the car as it defo makes 70 in first but maybe the calc sheet I have here is wrong?
That now works with 2.176 (not 2.716) giving 74mph at 7,200rpm.
Regards Dave
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