OK, so I've been rebuilding all the important stuff on a 79 F250 I acquired. Body is solid, but a rust bucket, motor rebuilt, new u-joints on all the axles, drain and reseal both axles, trasfer case, tranny, etc. Plowing/Hunt anywhere in the Rockies tractor ready to go (sooner rather than later, hopefully).

The problem is my local Napa - where the guys say they are old Ford guys - have given me the wrong parts at least a 1/2 dozen times since I started the project.

This time, they had all my seals/gaskets for the NP205 (mated to a T18 or is it T19?) in stock, except the front output seal. Well, I got it from them and it's Napa PN 15773. The diameter of the seal itself is too small to fit in the retainer and the seal hole for the output shaft itself is approx. 1 3/4", while needing to be about about 2 1/4". Pulling out the old seal out of the trash from the rear output (already done and put back together), it seems to be the right size by eyeball (Napa PN 21211).

I guess my question is, was there a smaller stock front output? After going through my truck, it's clear the truck was taken care of and upgrades have been done (good bud's granpa bought it new), so who knows? Is the front output/yoke diamter the same size as the rear? I just can't figure out how they can order me the wrong sized seal if it's just a stock part. Heading back down there and apparently need to know more than them.

Always appreciate the knowledge on this site...thanks for the help!

 

If you simply order the seal for a Np 205, you will get incorrect ones every time. These transfer cases used several different style yokes. Some had yokes that used a single joint, and these were available in different sizes. These used an entirely different ID for the seal, while others used a single joint, and up to a 1330 joint.
In some cases a 1350 double cardan joint was used, yet others mat have only had 1310's.
Yeah it gets confusing, but know that you should always use the part number that is stamped on the seal that you remove.
Just a FYI, most seals are based upon three critical measurements.
ID, OD, and thickness of the seal itself.
Some variables will come into play, such as how it mounts, but for the most part the three critical measurements are what you are looking for.
I seldom shop for seals or bearings by application. I shop for them by dimension and design.
This way, I am sure that a counter guy cant make a mistake.
A decent set of calipers can be very useful here.