Ford 9 third member swap to 4:11 post

[zuluking]

Need some advise for changing my 9 inch third member to a 4:11 post unit. I see Speedway has a lot of sets for a good price and all new components.

Has anyone used Speedway unit? 29 spine 4:11 posi with fill plug $870.

Cheers
Frank

 

[SteveL]

If your spending that kind of $$ on a 3rd member I would spend the extra and go 31 spline. Third member should cost the same you'll just need a set of axles. I recently snapped a 28 spline axle with 35s and an open diff.

 

[B RON CO]

Hi, if you are doing a lot of work to the Ford 9" you should add a drain plug. Good luck

 

[Broncobowsher]

Well you don't want 29 spline, nobody makes those. Judging from the other typos and how Broncos are made you are probably asking about 28 spline.

I've used a lot of Speedway products in the past, get what you pay for. Never bought a third member from them. Don't have any specific reason to avoid them. They are more of the old school hotrod shop and circle track parts.

Now for some tougher questions that we need feedback on to help with your choice. What size of tires, what transmission, how will the Bronco be used? What shape are the rear axles in now? Do you have worn sealing surfaces at the wheel bearings? Are the spline worn? What are your plans for getting the front axle to match gearing wise? Probably a few more later after those are answered.

We ask these questions to get a complete picture of what is going on. The 28 spline axles can be fine, but even Ford gave up on them and went to 31 later on in any axle that got and stress to it. Depending on what parts you need it can be a good idea to just make that part of the upgrade. Is the gearing the right choice? Is a limited slip the right choice? There are better choices at times that don't match the old school approach.

 

[zuluking]

Running a stock 302 with C4 and 32" tires. Axle bearings and seals are new. I haven't rebuilt ford 9 or Dana 30 yet. I run it around the street so not heavy offload. I have noise and know third member needs rebuild. The Bronco was a mud dragger from FLA so when I got it it had water in both axles. So I thought replacing it with a new third member would save me a lot of cost ,time, and headache.

Just thought I would ask for help since this forum has been so resourceful.

Yes I have fat fingers too so typos happen all the time. HAHA

Cheers
Frank

 

[SteveL]

The biggest expense when dealing with the front or rear end is swapping gears and or carriers especially if you're paying for the labor. That why it's nice to be sure what you need so you only pay for it once. That's why so many of us upgrade to 31 spline if you're paying to have one set up. I think wh sells a set of rear axles for about $260. Also if you plan to change the front from 3:50to 4:11 you need a different carrier or a set of "thick"gears to make it work. When doing the front the question it whether to invest that kind of money into the dana 30 or upgrade to a 44.