I am trying to figure out how to raise my gear ratio in my "chunk". I currently am still running the original differential. And to call it a three speed is not really true in today's world. It blows the tranny gasket if I run 50 mph in it. it doesnt like to get above 45. i have to be able to run it on the road but i keep getting different stories from my truck guys. one says it needs a 3.08 the other says a 3.50 or a 3.70. Help! Its a cruiseomatic tranny. its a 292 small v8. original is the condition of almost everything. im sorry i dont know what the current diff is in it. i am a newbie. <!-- / message -->I need to order parts and get this done but cant. Please post some input for me. Thanks guys!
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I assume it is a 9 inch and not a Dana rear end as Dana's typically run in F250's and up.

For daily driver and very light towing, a 3.00 pumpkin will work very well. Low RPM's at cruise. For medium heavy towing/hauling, I would go with a 3.50 or 3.70. All this depends on what you want to do with the truck really.

The pumpkin is straightforward in changing out. You can get one from a junkyard for less than $50 in most cases. New will run you more and Posi will cost a lot more. Figure 3 hours for changing out if you have never done before and 1-2 if you have good tools and jacks. The pumpkin is heavy, about 80 lbs. so figure that in when you pull it.

 

Hi thanks for the fast reply. I had a guy tell me he thought i had a 4.11 in there now. I dont want to haul much, i just like the truck for the truck. what about the "splines"? I hope i said that right. i heard they had to match. should i be looking for a 1960-1970 f100 at the junkyard? one guy said i could put a mercury in it but that is a car not a truck. i dont want to downgrade it so far that it wont haul a sofa. sorry to be ditsy but i am learning. thank you!

 

your truck will have a 28 spline unit unless it was changed for a 31 spline unit.

With the COM the tallest gear i would recommend would be the 3.25. 3.08 are chebby gears.

Look at the housing and tell us if it truly is a 9" rear.....

Danas were avalible in all F100s 61 thru 66, though much harder to find gear sets for.

As for the chunk being out of a Merc??????? a nine inch housing is a 9" housing weather it is in a car or truck.... As long as the splines match there is not much difference.

Probally the most popular gear set you will find in the yard will be 3.90 and 3.00

garbz