Help needed - calculating final gear ratio for T10M1 transmission

[6s1640]

Hi all,

I am having trouble calculating transmission final gear ratios.  Help me understand where I am going wrong.  Below is the table for the 65-66 T10M1 gear set.  By dividing the gear teeth by the corresponding cluster teeth should be the final ratio, but it does not match the advertised final ratio.  What am I doing wrong?

                  Advertised Final Ratio       Gear tooth count     Cluster tooth count   Ratio of gear teeth to cluster gear teeth
1st gear           2.36                                  36                              17                            36/17 = 2.12, should be 2.36
2nd gear          1.62                                   29                             20                           29/20 = 1.45, should be 1.62
3rd gear          1.20                                   27                             25                           27/25 = 1.08, should be 1.20
4th gear          1.00                                    26                            29                              26/29 = 0.90, should be 1.00

All four calculations can be corrected with the same "fudge factor" equal to 1.1154.

For example:

1st  gear  with 2.12 X 1.1154 = 2.36199, rounds to 2.36
2nd gear with 1.45 X 1.1154 = 1.61731, rounds to 1.62
3rd  gear with 1.08 X 1.1154 = 1.20462, rounds to 1.20
4th  gear with 0.90 X 1.1154 = 1.00000, rounds to 1.00

What am I missing?

Thanks

Cory

[s2ms]

Cory,

All gears are normalized to the 4th gear final ratio so for all the others you must divide their result by the 4th gear ratio of gear teeth to cluster gear teeth.

For example 1st gear: (36/17) / (26/29) = 2.36

Dave

[kram350]

Remember, one gear is driven and the other is a "drive" gear. Driven/Drive . Example 1st. gear; 36/17= 2.12 thru the cluster to 29/26=1.115. 2.12 x 1.115 = 2.36. Same for all.

[6s1640]

Cory,

All gears are normalized to the 4th gear final ratio so for all the others you must divide their result by the 4th gear ratio of gear teeth to cluster gear teeth.

For example 1st gear: (36/17) / (26/29) = 2.36

Dave

Hi Dave,

Okay.  Guess what 29/26 = 1.1154 Fudge Factor.  (or 1/(26/29) = 1/.8965 = 1.1154).  Below is a some info I pulled from the web.  It is describes the calculation you made.  I still don't understand, but will keep digging.   Somehow the 4th gear is driving all the other gears, thus the (drive/driven) ratio?  I guess it is time to pop a side cover off and turn the input shaft and see what gears rotate and which are the drive and driven.

Good deal

Cory

[OldGuy]

I think what is confusing the issue is the concept of inputing the "fourth gear ratio". In reality there is no fourth gear ratio because fourth gear is 1 to 1. When the gear selector is in fourth gear, the transmission main shaft is linked directly to the input shaft. In theory, you could completely remove the cluster gear from the transmission when the gear selection is fourth gear. It does nothing but rotate with no power being directed through it.

What you need to factor in to the equation is the ratio of the input shaft to the cluster gear (26/29) which many have said. The cluster gear rotates slower than the input shaft so by dividing the respective gear ratios by that of the input shaft/cluster gear you get the actual gear ratio.

Frank

[kram350]

I always "see" the power flow from input to output via the gear selected and forget all the other gears, which are just sitting there waiting their turn to be engaged. This way you can determine or "see" which are the driven/drive gears and work the math. A power flow diagram input to output thru the trans for each gear is helpful to understand this. As stated below 4th is full lock up.

Just a note that modern aftermarket T-10's have gears that are rollerized to help eliminate as much friction as possible when they are not engaged. The original (Shelby) T-10 gears ride slip fit on the output shaft causing more drag.