Fluid Motorsports upgraded differential service
#1
Fluid Motorsports upgraded differential service
Fluid Motorsports upgraded differential service.
We are now offering the RX-8 community a convenient way to upgrade the differential in your RX-8. This service will allow you to choose the gear ratio of your choice, have it built, shipped and installed in your RX-8 while keeping downtime to a minimum. This is a fresh rebuilt differential with a one year warranty.
The Process:
We start with a used differential in good rust free condition.
Step one:
Disassemble, clean and inspect the housing and internals to verify the donor is in good rebuildable condition.
Step two:
Replace all bearings, seals and install a new ring and pinion with the gear ratio of the customers choice.
Step three:
Bench test to ensure quite operation
The available ratios and prices are as follows:
3.90 - $1600
4.10 - $1600
4.33 - $1400
4.44 - $1500 Stock 2004-2008 rebuild
4.77 - $1449
During this process if you would prefer to install a Kaaz differential, contact us and we will advise you of the setup options for this high performance differential. We can make recommendations for the setup to best suit your needs.
This service will be performed within approximately one week of your order.
Eliminate Downtime
This swap can be performed by a competent mechanic (not necessarily a rotary mechanic) in less than a day.
To eliminate vehicle downtime, we can provide you with a fresh rebuilt unit shipped to you or the installation facility. This will allow you to drive your vehicle to your installer and have the swap performed usually the same day! There is no additional cost to you for this service, we will bill you a 100% refundable core charge of $400. Once your original differential is returned in good re-buildable condition we will refund your $400.
Alternatively if you prefer, you can ship us your differential and we will perform this service to you OE differential.
Please PM to arrange Ordering Options.
We are now offering the RX-8 community a convenient way to upgrade the differential in your RX-8. This service will allow you to choose the gear ratio of your choice, have it built, shipped and installed in your RX-8 while keeping downtime to a minimum. This is a fresh rebuilt differential with a one year warranty.
The Process:
We start with a used differential in good rust free condition.
Step one:
Disassemble, clean and inspect the housing and internals to verify the donor is in good rebuildable condition.
Step two:
Replace all bearings, seals and install a new ring and pinion with the gear ratio of the customers choice.
Step three:
Bench test to ensure quite operation
The available ratios and prices are as follows:
3.90 - $1600
4.10 - $1600
4.33 - $1400
4.44 - $1500 Stock 2004-2008 rebuild
4.77 - $1449
During this process if you would prefer to install a Kaaz differential, contact us and we will advise you of the setup options for this high performance differential. We can make recommendations for the setup to best suit your needs.
This service will be performed within approximately one week of your order.
Eliminate Downtime
This swap can be performed by a competent mechanic (not necessarily a rotary mechanic) in less than a day.
To eliminate vehicle downtime, we can provide you with a fresh rebuilt unit shipped to you or the installation facility. This will allow you to drive your vehicle to your installer and have the swap performed usually the same day! There is no additional cost to you for this service, we will bill you a 100% refundable core charge of $400. Once your original differential is returned in good re-buildable condition we will refund your $400.
Alternatively if you prefer, you can ship us your differential and we will perform this service to you OE differential.
Please PM to arrange Ordering Options.
#7
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#8
Pulled this from the other thread in my Section.
Thanks Craig for Running the numbers
Thanks Craig for Running the numbers
Originally Posted by Zeon
I took the time to do some calculations for rpm at different speeds for the different differential ratios available through Fluid as per this thread, so I figured I would just pass it on to everyone in case they were interested. Below are my assumptions, followed by my calculations.
WARNING: All values are calculated meaning this does not necessarily directly correspond to real world situations.
Assumptions:
Gear Ratios (I was only worried about the 2004 6-speed)
Taken from: link to transmission thread I grabbed ratios from
1st = 3.76
2nd = 2.269
3rd = 1.645
4th = 1.187
5th = 1.000
6th = .843
Constants:
mms to inches conversion factor = 1/25.4
MPH to inches conversion = 1056/pi (info grabbed from this thread on another forum)
Tire Size = 225/45 R18
From this we infer:
nominal width of tire = 225
ratio of height to width of tire = 45%
rim diameter code = 18
** I just wanted to note that there is a difference in my calculated values when compared to the thread I linked above. I calculated the tire diameter below to be about 26", I cannot say if this is correct or not as I haven't measured my wheels/tires to compare. The thread I linked appears to be using a tire diameter value of 24.223113865" for some reason which wasn't explained in the thread. I have confirmed my calculation with different tire size calculators online, so I'm just going with it. So just keep in mind that the actual speed could be slightly off as I mentioned in my warning. **
Formulas:
Tire Diameter = (nominal width of tire * ratio of height to width of tire * 2 * mm to inches conversion factor) + rim diameter code
Note: the ‘2’ in the above formula is to take both sidewalls into account for the total wheel + tire diameter
MPH = (RPM * tire diameter) / (gear ratio * differential ratio * MPH to inches conversion)
From that we can derive the formula for finding RPM at a given speed
RPM = (MPH * gear ratio * differential raio * MPH to Inches conversion) / tire diameter
Results:
Maximum MPH per gear
-------------------------------------------------------------
Gear Differential ratio
- 3.9 4.1 4.33 4.44 4.77
1 47 45 43 42 39
2 79 75 71 69 64
3 108 103 98 95 89
4 150 143 135 132 123
5 178 170 161 157 146
6 212 201 191 186 173
RPM @ MPH
-------------------------------------------------------------
30mph
Gear Differential ratio
- 3.9 4.1 4.33 4.44 4.77
1 5693 5985 6321 6482 6964
2 3436 3612 3815 3911 4202
3 2491 2619 2766 2836 3047
4 1797 1890 1996 2046 2198
5 1514 1592 1681 1724 1852
6 1276 1342 1417 1453 1561
45mph
Gear Differential ratio
3.9 4.1 4.33 4.44 4.77
1 8540 8978 9482 9723 10445
2 5154 5418 5722 5867 6303
3 3736 3928 4148 4254 4570
4 2696 2834 2993 3069 3297
5 2271 2388 2522 2586 2778
6 1915 2013 2126 2180 2342
60mph
Gear Differential ratio
3.9 4.1 4.33 4.44 4.77
1 11387 11971 12642 12964 13927
2 6872 7224 7629 7823 8404
3 4982 5237 5531 5672 6093
4 3595 3779 3991 4092 4397
5 3028 3184 3362 3448 3704
6 2553 2684 2834 2906 3122
70mph
Gear Differential ratio
3.9 4.1 4.33 4.44 4.77
1 13285 13966 14749 15124 16248
2 8017 8428 8901 9127 9805
3 5812 6110 6453 6617 7109
4 4194 4409 4656 4775 5129
5 3533 3714 3923 4022 4321
6 2978 3131 3307 3391 3643
I have no idea how bad the formatting is going to be for this, so I have attached a zip containing the .xls file where I have made a little basic calculator. In this simple calculator, you can change all values that are highlighted in yellow and it will automatically update the correct information.
I hope this is helpful to anyone out there considering a differential gear change and if someone finds an issue with any of my calculations PLEASE let me know and I will be sure to update the .xls and this post.
WARNING: All values are calculated meaning this does not necessarily directly correspond to real world situations.
Assumptions:
Gear Ratios (I was only worried about the 2004 6-speed)
Taken from: link to transmission thread I grabbed ratios from
1st = 3.76
2nd = 2.269
3rd = 1.645
4th = 1.187
5th = 1.000
6th = .843
Constants:
mms to inches conversion factor = 1/25.4
MPH to inches conversion = 1056/pi (info grabbed from this thread on another forum)
Tire Size = 225/45 R18
From this we infer:
nominal width of tire = 225
ratio of height to width of tire = 45%
rim diameter code = 18
** I just wanted to note that there is a difference in my calculated values when compared to the thread I linked above. I calculated the tire diameter below to be about 26", I cannot say if this is correct or not as I haven't measured my wheels/tires to compare. The thread I linked appears to be using a tire diameter value of 24.223113865" for some reason which wasn't explained in the thread. I have confirmed my calculation with different tire size calculators online, so I'm just going with it. So just keep in mind that the actual speed could be slightly off as I mentioned in my warning. **
Formulas:
Tire Diameter = (nominal width of tire * ratio of height to width of tire * 2 * mm to inches conversion factor) + rim diameter code
Note: the ‘2’ in the above formula is to take both sidewalls into account for the total wheel + tire diameter
MPH = (RPM * tire diameter) / (gear ratio * differential ratio * MPH to inches conversion)
From that we can derive the formula for finding RPM at a given speed
RPM = (MPH * gear ratio * differential raio * MPH to Inches conversion) / tire diameter
Results:
Maximum MPH per gear
-------------------------------------------------------------
Gear Differential ratio
- 3.9 4.1 4.33 4.44 4.77
1 47 45 43 42 39
2 79 75 71 69 64
3 108 103 98 95 89
4 150 143 135 132 123
5 178 170 161 157 146
6 212 201 191 186 173
RPM @ MPH
-------------------------------------------------------------
30mph
Gear Differential ratio
- 3.9 4.1 4.33 4.44 4.77
1 5693 5985 6321 6482 6964
2 3436 3612 3815 3911 4202
3 2491 2619 2766 2836 3047
4 1797 1890 1996 2046 2198
5 1514 1592 1681 1724 1852
6 1276 1342 1417 1453 1561
45mph
Gear Differential ratio
3.9 4.1 4.33 4.44 4.77
1 8540 8978 9482 9723 10445
2 5154 5418 5722 5867 6303
3 3736 3928 4148 4254 4570
4 2696 2834 2993 3069 3297
5 2271 2388 2522 2586 2778
6 1915 2013 2126 2180 2342
60mph
Gear Differential ratio
3.9 4.1 4.33 4.44 4.77
1 11387 11971 12642 12964 13927
2 6872 7224 7629 7823 8404
3 4982 5237 5531 5672 6093
4 3595 3779 3991 4092 4397
5 3028 3184 3362 3448 3704
6 2553 2684 2834 2906 3122
70mph
Gear Differential ratio
3.9 4.1 4.33 4.44 4.77
1 13285 13966 14749 15124 16248
2 8017 8428 8901 9127 9805
3 5812 6110 6453 6617 7109
4 4194 4409 4656 4775 5129
5 3533 3714 3923 4022 4321
6 2978 3131 3307 3391 3643
I have no idea how bad the formatting is going to be for this, so I have attached a zip containing the .xls file where I have made a little basic calculator. In this simple calculator, you can change all values that are highlighted in yellow and it will automatically update the correct information.
I hope this is helpful to anyone out there considering a differential gear change and if someone finds an issue with any of my calculations PLEASE let me know and I will be sure to update the .xls and this post.
#12
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Glad to help, as I said if anyone finds any issues with my numbers please let me know. Also, check out the thread if you want to calculate RPM at any other speeds, I have attached an excel sheet with all of my calculations in it.
#13
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Do they use the stock gear ratios for each gear though? I imagine that a race team would probably have a fairly custom tranny setup... I mean, with different trans gearing 5.12 might be the perfect diff gear ratio.
#16
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Please forgive my nubness, but why do you say the 4.1 rear would beat a 4.44 rear 8? I thought that the lower the final drive the longer the gears were, but acceleration suffered from the lengthening of a gear. Would it be faster just due to the fact that it wouldn't take as many shifts to go the distance?
#17
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What rpm range does a race car need to be in most of the time and what rpm range does a street car drive around in most of the time? If you say the same thing I'm going to laugh at you. You CAN NOT compare what a race team needs on a track to what a street car needs. It's not anywhere remotely the same. Not even for the same engine.
#18
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Please forgive my nubness, but why do you say the 4.1 rear would beat a 4.44 rear 8? I thought that the lower the final drive the longer the gears were, but acceleration suffered from the lengthening of a gear. Would it be faster just due to the fact that it wouldn't take as many shifts to go the distance?
#19
im sorry, but i have never had any reason to learn anything about differentials. So basically what im asking is what does it matter? is it the lower the ratio, the more acceleration, but lower top end, and the higher the less acceleration and higher top end?
#20
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I wouldn't say that the 4.10 would be faster in acceleration than the 4.44. If it is slower though, it's not enough to matter and most likely any wheel spin/driver error is more than enough to make up the difference. The 4.44 equipped cars accelerate faster than the 4.77 equipped cars due. Shifting takes time. More is not always better. There comes a point where more is worse and uneccessary. It's somewhere right around a 4.10 or so as I find the 4.44 completely worthless and the 4.77 downright terrible. I'm sorry to all of you RX-8 owners out there but all of your differential ratios suck and your cars drive is a bit substandard as a result. Fortunately you can fix it. I'll keep my 4.10 in my RX-7 anyday. Even with less power and even with only a 5 speed.
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