16/27 cluster

27TV8

27TV8

Member
I picked up a -78 top loader gearbox with an open drive "Pickup" output
It has a16 tooth input and a 27 tooth on the cluster? Should there be such a combination? or is this a mix up? I have a 16/28 now. The same top loader and open drive.Am not sure this has been used the way it is. As this does not add up to te standard 44 I am curious.
Thanks
 
27TV8 said:
I picked up a -78 top loader gearbox with an open drive "Pickup" output
It has a16 tooth input and a 27 tooth on the cluster? Should there be such a combination? or is this a mix up? I have a 16/28 now. The same top loader and open drive.Am not sure this has been used the way it is. As this does not add up to te standard 44 I am curious.
Thanks
Click to expand...

The "Rule of 44" always applies.......EXCEPT when it DOESN'T! I've heard of a 29/14 in SOME Mercury transmissions, and like in your case, a 27/16 combo in some '51-ish pick-ups. That's all I know. DD
 
Yeah.... the “rule of 44” has plenty of exceptions. In your case, you have a transmission gearset from 1951-52 (open drive 3 speed pickup truck transmission). That gear tooth combination continued on into the late 50’s in both cars and trucks. Many other non-44 combos exist as well.
 
Mac VP said:
Yeah.... the “rule of 44” has plenty of exceptions. In your case, you have a transmission gearset from 1951-52 (open drive 3 speed pickup truck transmission). That gear tooth combination continued on into the late 50’s in both cars and trucks. Many other non-44 combos exist as well.
Click to expand...

And do not mix those gears with the earlier 36-48 car and 36-50 pickup gearsets, different pitch on the teeth.
 
Thank you I was curious how there could be 16 tooth for 26 and or 27 tooth clusters?
Has to be some difference.
How to tell? is there p/n etched on the inputs? They all look the same.
I had better get Van Pelts book.
Had a failure the other day a tooth broke off the input and got between the cluster and ruined everything. Hope the case did not crack! I have been running this trans for 20 years and no problem then Kapow!
 
27TV8 said:
Thank you I was curious how there could be 16 tooth for 26 and or 27 tooth clusters?
Has to be some difference.
How to tell? is there p/n etched on the inputs? They all look the same.
I had better get Van Pelts book.
Had a failure the other day a tooth broke off the input and got between the cluster and ruined everything. Hope the case did not crack! I have been running this trans for 20 years and no problem then Kapow!
Click to expand...

The later 16T input is approximately 1/16 larger dia on the gear OD than it's earlier Ford counter part.
 
Agreed with above. the gearset is usable as a complete set but no interchangeability with anything else. It is virtually impossible to use that gearset for a closed drive conversion too.
If you want to use it in an f1 and it is in good condition you're good to go.

To my eyes the gears have a more "pointy" appearance to them and if you look carefully there is a difference in the helix angle on the gears. This results in a difference to the helix angle on the shaft and also don't forget the reverse idler and the 1st/reverse synchro sleeve.

Mart.
 
The 81A-7017 and 8M-7017 are interchangeable 16 tooth drive gears. They have a gear diameter of approximately 2.35”. They work with the 68-7113 and 8M-7113 cluster gears (28-24-18-14 teeth) and are used from 1939-48 cars and 1939-50 pickup truck 3 speed transmissions. They also honor that good old 44 rule.

The 1C-7017 is the 16 tooth drive gear that is used in the 1951-52 pickup truck 3 speed transmission. The diameter of the gear is 2.45”. This is the gear that is matched to the 1A-7113 cluster gear (27-23-17-13 teeth). The .010” difference in diameter is very difficult to “see” with the naked eye but it easily measured with a caliper.

Don’t attempt to mix the use of these three gears. The earlier ones would have a sloppy fit in the mesh with the later cluster gear. The later gear would create a VERY tight gearset that you would have to force together.

And there you have..... the rest of the story.
 
Thankyou all!
I will take my other spare apart today ,clean everything and do an appraisal and determine what I need.
Mr Van Pelt you will get an order soon including your book.
Thank you for the help.
 
When I had my 46 I couldn't find a good cluster gear, found a later partially apart transmission without the overdrive unit laying on the ground in a junkyard , the teeth looked different, and ther was one less tooth on the driving gear, had loose needles on the counter shaft, went together fine, rotated smoothly and was quiet, and survived much abuse,--- this was before the Internet and i wasn't told it couldn't work
 
27TV8 said:
I picked up a -78 top loader gearbox with an open drive "Pickup" output
It has a16 tooth input and a 27 tooth on the cluster? Should there be such a combination? or is this a mix up? I have a 16/28 now. The same top loader and open drive.Am not sure this has been used the way it is. As this does not add up to te standard 44 I am curious.
Thanks
Click to expand...

Go to Mac Van Pelt's website and you will find most, if not all, of the cluster and input gear combinations used in the early Ford, Mercury, and Lincoln top and side load transmissions.
 
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