Guys I have asked you in the past on what gear would I need for my truck. I have been looking for a 3.50 like you said well you guys taught me how to check them if they are in the truck. I found one today a guy has at an old junkyard already pulled from 72 ford he said he thinks it is a 3.50 but not sure. He wants only 50 bucks and stands behind it 100%. It has third member and both axles. My question is with it pulled how can I look at it and tell out of the truck what size it is. All responses very welcome.


Thanks


Keith

 

I was told you just count the number of teeth on the pinion gear and divide it by the number of teeth on the ring gear. But it's been awhile, so I might be wrong...

Marty

 

Look for the ID tag on the carrier. It's supposed to be between two of the bolts. Post the numbers and someone here can decode it.

If there's no tag, spin the axles and count the revolutions of the pinion.

Or, take the pinion retainer off (5 bolts) and count the teeth on both gears. If there's 10 on the pinion and 35 on the ring, it's 3.50:1 (or 350s).

Divide the ring gear by the pinion (35/10=3.5) to get the ratio.

Hope this helps.

Kevin K.

 

[updated:LAST EDITED ON 12-Sep-02 AT 03:17 PM (EST)]If there are 35 teeth on the ring could I just count the teeth there and be close or does a different pinion throw that out the window. I dont remember seeing a tag on third member.


Keith

 

Even with the pumpkin out (the center section if it is an 8" or 9" rear) it is sometimes hard to see all the teeth on the pinion. Line up a tooth on the ring gear with some part of the case where you can be sure to realign it again. Mark that tooth with a magic marker. Now, spin the pinion around and count it's revolutions until the marked ring tooth lines up again. if you spun the pinion around exactly 3 1/2 times, it's a 3.50, if you spun it 3 1/4 times, it's probably a 3.23 and so on. If the pumpkin is not out, you can try spinning the pinion and watching an axle, but if it's not a posi, sometimes the axles turn in different directions when you try this, and the count is not truely accurate. Polkat

 

if you take the center section out the ring gear should have 35 teeth and the pinion should have 10

 

Polkat I'll try that what you said. This guy has third member pulled out so that will give me the info I need. I have another question though the bolts on front of the 9 inch axle is that only thing holding the third member in. I am wanting to try and do this change out myself. Thanks for all the help and info you guys have been posting. I have really learned alot on this site.


Thanks

Keith

 

I think you'll need to pull the axles out a bit first before the center section will come out. It probably makes it a lot easier anyway

 

Yea, you do have to pull the axles out a bit so they will clear the carrier. It's better to pull them all the way out, as if you let them hang there, they can damage the axle seals, but then again, if the seals are old and hard, it's a great time to change them as well. Also, with the axle out, grab the bearing with one hand and spin the axle slowly with the other. You'll be able to tell by the feel if the bearings are getting gritty and worn. Then just pull all the nuts off the front (it should be nuts, not bolts) and the pumpkin will just come out. Mind that it's HEAVY, and best to lower it with a jack then try and use your hands!!! When it's out try to check the pinion bearing for slop! Usually the pinion bearings stay good, but I've seen loose pinion nuts (even though the torque used on these is heavy) and sometimes the crush sleeve (a little sleeve between the two pinion bearings that holds them tight at torque) can relax, especially if someone torqued the pinion nut twice without changing the sleeve.

You can also read up on using gear dye to check that the ring and pinion are meshed properly. I believe that the Motors Manuals and Chilton books demonstrate how to do this. The Ford 9" can be modified into a great race rearend, but it's pretty much bullet proof just as it stands!! Polkat