1970 F100 Ranger, 390, 2wd, BW T-85

Axle code on the Warranty tag is 08

Truck is supposed to have a 3.50 gear in it

So, I was investigating the rear axle and what the tag read (tag missing) to see what exactly I might need in the event that I wanted to rebuild the thing. Thats when I realized that I had a case with casting numbers D2SW-C and knew right off that was at least a 72 number, and what I believe to be for a T-Bird. I think there are 2 date codes that actually puts it in June of 73. I tried to include pics of these numbers and wanted your opinion, or if that's right.

If that's right, why would I have that case in the truck?? because none of the rear axle looks like it's been messed with in years especially the housing, if ever. I wonder if it was possible that the case could have been replaced by Ford along about 73 for a warranty issue or something, or did some clown just throw it in there for whatever reason? Wondering what I'm dealing with and if they're even 3.50 gears at all and how to tell? Typically what casting numbers would it have come with? Thanks, Always appreciate your help.

KOT390

 

Turn the tire and count driveshaft rotations. One rotation of the tire = 3.5 turns of the driveshaft

 

Yeah, I will do that. Moreover wondering if anyone had any ideas as to what case I have or why. Is it the same as what would have come in the truck originally? Thanks

KOT390

 

A missing tag is a pretty good indication the center section has been swapped out. Almost full sized Ford made for 30+ years had some version of a 9 inch and the most common is what these trucks have, also many passenger cars.
Counting the rotations is as simple what'shisname said, if it's a limited slip. If it's open (which it probably is) then leave one tire on the ground and turn the other tire 2 revolutions while counting driveshaft revolutions.

 

I know it is not limited slip, it is open. I will be able to check rotation later, just still wondering if anyone knows anything about that particular case that I have and what case SHOULD I have in it. I would like to replace it with the "correct" one when I rebuild it, rather than some T-Bird thing. Thanks

KOT390

 

While a missing tag can be an indication that 3rd member could have been swapped out, it also could just be an indication that someone simply pulled the 3rd member to change out the gear oil and was just too lazy to put the tag back on the stud, before tightening the 3/8"-24 self-locking nut back down.

"S" is the code letter for the Thunderbird vehicle line but, I dont know that that necessarily means it was ever actually installed in a Thunderbird. "T" is the code letter for the truck vehicle line but, there are "T's" sometimes present on parts on vehicles that aren't trucks.

If the 3rd member actually came from a Thunderbird, I would imagine there would be a cast-in 'hood' sticking out off the pinion housing for the pinion snubber. That's not present on the pinion housing you have shown and trucks don't use pinion snubbers on the 3rd member.

This is the original 3.50 geared, single track, 28-spline, 9-inch 3rd member I pulled from the rear end in my truck (I replaced it with a 3.50 geared, 31-spline, Traction-Lok, N-case, 9-inch 3rd member). This is the common C7AW-E 3rd member case you would find in a Bumpside 9-inch rear end housing.



Notice the (5-bolt) pinion housing casting number is C5AW-4668-A. The "A" in the string indicates the full-sized Ford vehicle line but, it definitely isn't a "T". This component from the '65 model design carried over into '69, unchanged. The casting date of the pinion housing is "8J21" --September 21st, 1968. The 3rd member case casting date is "8G25" --July 25th, 1968. Both these casting dates corresponds with my truck's build date so, the 3rd member is original to my truck.



The 3rd member case engineering number will be found on the inside, next to the right hand differential bearing stand --3rd member would have to be pulled from the housing to see this number. C7AW-4025-E (C7AW-E case).



Since this 3rd member is a 3.50 ratio, that means the gears are timed (non-hunting). You can still see the yellow painted timing marks on two adjacent ring gear teeth, indicating where the gears were lapped in at the factory. (there's a yellow paint mark on one of the pinion gear teeth that matches up to these two timing marks on the ring gear).

 

Don't overthink the part number. Just remember, all those early 90's mustangs had heads that said E7TE. And it was a good explanation by ultraranger about the pinion snubber that you don't have.

 

Right, I'm glad to hear about the snubber that is not present in mine as that makes me think that maybe it was replaced as a warranty situation maybe sometime in 73, For whatever reason. Thanks for that info Ultra, much appreciated.

I also agree, not to overthink the situation other than the fact that my truck is a 70 and this 3rd member clearly is not original with a 72 casting # and a 73 date code. That's the only thing that makes me wonder why, or what. If it were the other way around, with something from 67-69 for example I wouldn't have thought much of it. I'm going to go out shortly and try to check the ratio. As long as it's a 3.50 like is supposed to be in there I probably won't worry too much more about it. Thanks again.

 

UPDATE: I just checked the ratio and now my ignorance on rear axles may start to show. I raised just the passenger side rear wheel and there is one tire revolution to 1.75 driveshaft revolutions. That doesn't sound right unless it's because I only had one wheel raised? 1.75 is half of 3.50...Not sure what's going on now.

 

Yes. 3.50 is what you have.

 

Apparently didn't read my post where I said turn the tire 2 revolutions. It's because of the spider gears, if one tire stops the other one goes twice as fast. 3.50s

 

Yes I read it but I guess I missed the 2 revolutions part. I've noticed It's common for most of us to miss little things in one anothers posts here from time to time, and admittedly it can be frustrating. Thanks for the help though. I think I will call it good at this point. It is what it is.

KOT390

 

I don't know how long you've had this truck, whether it's a short time or a long time? Either case, if you don't know the history on the truck or rear end and if you've never done any sort of service work on the rear end, it would probably be a wise move to lift the rear up, remove the wheels/tires, pull the axles out and remove the 3rd member from the housing, clean the housing out and check the 3rd member ring and pinion gears for wear, chipped or broken teeth and its general, overall condition. It would also be a good idea to look at the splines, on the ends of the axles, to see what condition they're in.

With the 3rd member out, you'll be able to actually count the number of ring gear and pinion gear teeth. Divide the number of ring gear teeth by the number of pinion gear teeth and you'll know your exact ratio, without any guessing of turning wheels and counting tire/driveshaft revolutions. Especially with an open differential, slippage can occur that can make the revolution counting process inaccurate.

This would be a good time to replace the axle bearings and seals as well. Put fresh gear oil in it (5-pints --requires all of 2 bottles and half of the 3rd bottle), button it up and ride on with some peace of mind and in knowing exactly what's in there without the mystery of guesses or unkowns.

 

Hey Steve. I most certainly appreciate your input. I have read a lot of your posts on the subject. So, I have only had the truck about 6 months and have done a few various other improvements as I drove it. I was thinking that I should address the rear axle for just the reasons you stated, bearings seals and inspection. That's what made me start investigating that area. I have never messed with a rear end so this will be good. I don't suppose you know of any links to threads on this process, maybe with pics do you? Maybe a sticky thread? Thanks

KOT390

 

Removing the axles and 3rd member is pretty easy --well, assuming the axle bearings don't have surface rust on them that seizes them to the bearing bores at the ends of the axle housing tubes.

After you lift the rear end up and the wheels are off, take a brake spoon and back the brake adjusters off so the shoes will retract away from the inner friction surfaces of the drums and then remove the drums.

You'll need a 3/4" socket to remove the (4) 1/2"-20 nuts on the stamped steel axle retainer. Access to the nuts will be through the large hole in the wheel flange of the axle.

Once the (4) 1/2" nuts are removed, the axle can be pulled out of the housing (the 3rd member won't come out until the axles are removed first). If the axles are stuck to the bearing bore and won't pull out by hand, don't beat and bang on the wheel flanges of the axle with a steel hammer. You're just going to put flat spots in the wheel flange before you can get it loose. Use a brass hammer or, the proper tool to pull them free --a slide hammer.

Once the axles are out, you'll need to remove the (10) 3/8"-24 self-locking nuts from the studs holding the 3rd member to the housing. This will require both a 9/16" socket and a 9/16" end wrench, since you won't be able to get to the two lower nuts at the bottom of the 3rd member with a socket.

If there are (10) copper washers (one on each of the 10 studs), you'll need to remove them before the 3rd member will come out. Put a catch pan under the 3rd member and pry the 3rd member loose from the housing. Once it separates from the housing gasket, the (smelly) gear oil will start to pour out. Let the oil drain out for a while and then remove the 3rd member from the housing. An open (single track) 9-inch 3rd member will weigh roughly 68 lbs. A 9-inch 3rd member with a Traction-Lok differential will weigh roughly 72 lbs so, be ready for some weight when it clears the tips of the housing studs.