Need to slightly lower rear end gear ratio. My '68 F100 2wd 9" currently has the OE 3.25 gears. Found a set of Ford 3.50 gears, C2AW4210B, that look pretty good with minimal pitting.
Will the 3.50 gears drop in without mods?
My knowledge says so, but would like to verify.

 

If the gears are from a 9-inch rear end, they will swap over.

There's surface rust and then there's pitting. If the gear teeth are pitted, you may wind up with a noisy/howling set of gears in the rear end.

 

New gears are less than $200.

Why are you swapping ratios? A 3.50 will raise rpm by around 150.

 

351,
Interested in going a bit lower with gearing 'cause truck is on 32" BFG's and used for offroad and chasing trails @ tymes.

 

I would recommend 3.70 or maybe 3.90 gears. You could go lower if you don't run the highway much. But those will still let you do everything fairly comfortably.

 

Thanks.
Already have Oregon Performance low gear kit. I think going 3.70 might be slightly much, especially here with the real world hiway speeds of SoCal. Just needing a little bit more.
Sorry I left those details out earlier.
*Ford C6 Low Gear Planetary Set C-6 Automatic Transmission Lower Gears Lincoln Mercury Kit: Oregon Performance Transmission - Rebuild Parts for 700R4 4L60E 4L80E E4OD 4R100 47RE 48RE & More

 

Thank you for the input .

 

My '66 has a 240 in it and had 3.50 rear gears before the pinion broke some teeth. I put in another rear end with 3.00 gears. The 240 liked the 3.50 gears better. I use it as a daily. I spend more time in 2nd gear at higher rpms now. For mostly in town driving, my mpg's dropped from16+, to 13+. Handles 65 on the freeway much nicer. Also, starting off, it's a real dog. 235/75/R15 tires, and three on the tree.

 

If you're putting out the money for this, I definitely wouldn't put in a used pitted R&P. New quality ones are pretty cheap. Too much chance of getting noise out of a used set IMO, as you might even get noise if you don't hit the exact wear pattern it has from original install. Not worth the aggravation in my world, but then I'm getting old and loosing my patience for doing things more than once and beating myself up

 

3.25 Mayb

 

If swapping gears, normally the carrier's change at the 3:73 mark.
If wishing for 4:10's, then you'd have to obtain another carrier assembly. I wouldn't recommend a ring gear shim.

Ok, so I was running 3:50 gears with 255-16 tires behind a 300-six and NP435 trans. way too high geared for my hilly terrain.
After about 4-years, I swapped to 4:10's which work great, except for high-speed expressway travel.
Food for thought: I'm running and have been since 2004, a mis-matched ring and pinion in my Dana 60 rear w/ no problems.

 

There is no carrier break in a 9 inch.