Thiokol, C4 Auto Transmission to a OC-4 Manuel Trans

Here's some hopefully useful info.

pics in order are;

neutral
first gear
second gear
third gear
fourth gear
reverse gear

I have a speed/ratio chart I'm trying to add, next post I guess.
-Pat

Ground speed vs. gear ratios for OC-4

Thiokol 1200A 12 tooth sprocket / 4 inch track pitch.

3000 RPM engine speed. Firm snow level ground

(calculations ignore Automatic trans slip)

Input shaft (mainshaft/upper shaft) 3000 rpm


Gear / Tooth count / Ratio / Total ratio / Axle RPM / Speed MPH


1st 13/36 2.77 39.85 75 3.41

2nd 17/31 1.82 26.24 114 5.18

3d 21/27 1.29 18.5 162 7.36

4th 39/32 .82 11.81 254 11.55

Rev 13/31 1.82 2.38 (w/ 21 tooth idler gear)

R&P 6/37 6.17
(Total R&P and DB = 14.389)
Drop Box 15/35 2.33

Recalculate by dividing Speed MPH by 3000 RPM
then multiply result by desired RPM

Alternate Drop Box gears are 18/32 for 1.78 ratio
Alternate sprocket 9 tooth/ 4 inch pitch


Table compiled by Spryte Improvement LLC.

My math may be in error please correct where needed

(After two hours of trying, the table did not download to the forum very well, sorry).
-Pat

I hope this is right! Thank you Pat for the information as always you are great!!! I hope you are ok with me adding the Ford AOD data at the end. Any problems let me know.

/rk

Very nice chart. Thank you!
-Pat

Well summer has come and gone and none of us have gotten done what we had hoped to (RIGHT?). At least I haven’t.

Here's an update on the Ford C4 Automatic Transmission to OC-4 Manuel Transmission that turned into the Ford AOD (Automatic Over Drive) to OC-4 Manuel Transmission project. It’s on the back burner!!! Everything is bought but now I’m re-tracking the cat for the fast approaching winter. We will see how things go and look at it later.


Here are some pictures of:

• New axles (non-lock ring type), New axle bearing and seals (from Spryte Improvement in Wallace Idaho) in the OC-4 installed
• New OC-4 Drop boxes and Rear end Summit Racing Differential vent installed with cut off valves.
• Raised Drop Box oil fill holes to hold 3 Qt of Shell Transmission Oil.
• New OC-4 gaskets (sick of the leaking)
• Dismantling of the old track preparing then for the new rubber
• Removed fuel tank due to a leak somewhere

Has anyone ever thought of putting two ½” pieces of rubber in the open warn out 6" long, 1" wide, 2" deep hole in the center of the warn out grouses? This would fill the hole, give it stealth and help with hard surface future ware, would it not? It would act like a rubber tire, sort of. I'm thinking about doing this I have a tons of left over belting and can drill two ¼” holes with two ¼” bolts though it to hold it in?
/rk

Anyone know where to get an new 16~20 gallon replacment Aluminum fuel cell made? $200~$350?
/rk

You can try aerotanks.com if it needs to be somewhat costume.

Thanks for the aerotanks.com lead. Here is some ebay stuff I found also. Somthing will work out.

/rk