All,

So, I think I have a line on a pre-1970 F-100 9" rear-end with 3.50 gears. I currently have the stock 3.92 Dana 44(45?) rear-end in my '51. Based on what I've read here (mostly the musings of mtflat) the 3.50 gears are good for highway cruising, but not too high, for the stock flathead (I've got the stock inline 6 and the crash-box 4-speed, all of which I will be keeping). My question now is, assuming this is the correct rear-end, what should I should I be looking for to make sure this particular one is not junk (i.e. any tell tale signs, etc.)?

Also, if I go ahead and get this done (which seems like a good thing because cruising down the freeway at 55 tops isn't all that great) are there other things that I haveto/should do that go along with it (such as relining the brake drums, fabricating shock mounts, maybe repalceing the shocks/springs)... anything you all can think of would be welcome advice? Thanks.

 

More then you ever wanted to know;

Kevinstang's Ford Nine Inch Differential Page +

Plus read;

https://www.ford-trucks.com/forums/6...-articles.html

 

I'm doing this now. The rear I got had like new brakes and even a spring kit. I was able to use the stock 1952 emergency brake lines. I only paid $150. I pulled the center chunk after I got home and the gears look fine. I did not see any chips or chunks missing and I did not see any hot spots either. I do not feel an excess rotation play.

You will need new shock mounts, ubolts, ubolt plates and any brake parts if necessary. It's fairly easy job. Disconnect the brake lines, emergency brakes parts and driveshaft. Use a 4" grinder to cut the old ubolts. I placed jack stands right behind the cab under the frame. After everything was cut I used a jack to lower the rear and rolled it out. (keep the brake drums on)

You got lucky with the 3.50 I'm stuck with 3.75 it'll do until I can put in an overdrive. BPB blaster is your friend. I used stock style lower spring mounts with the shock mounted attached. Looks just like the factory but 3" tube. I have a set of lower shock mounts that bolt under the spring pack if you decide to flip the ubolts or find a set of spring mounts without the shock mounts. You'll under stand when you look at the spring setup. I'm stuck on the shocks right now pins are rusted to the frame..

good luck

bob

 

If BPB blaster is your friend then Oxy / Acetylene is your lover, honest!

 

No Limit make a mounting kit for this conversion . I would suggest new U -bolts & nuts .A part of the kit .

 

There's really nothing that you 'have' to do, unless you see something that is obviously broken, but there might be a couple thing you'll want to do, just for peace of mind. If it were me, I'd check the brakes and repair/replace as necessary. If it's been sitting a while, new wheel cylinders, at the very least, would be a good idea. I'd also pop out the center section and inspect and clean that up, make sure there's no nasty gunk in the bottom of the housing, and put it back together with fresh 90wt. Then put it in the truck and drive it. If it doesn't make any wierd growling noises, you're good to go. If you have strange noises, you replace an offending bearing or two, and you're good to go. Either way, it's no big deal.

As far as replacing springs, I wouldn't, unless there's a problem with yours currently, or you planned to do it, anyway. Shocks, same thing. Do they need replacing now?

I did this swap the first time as a 16 year old kid back in the late 70's. I don't recall having an issue with the rear shocks. I seem to remember the rear housing having a shock mount welded to it, and I was able to use that to attach my shocks to it. I personally took the rear from a 68 or 69 F-100. The stock e-brake cables worked, too. I also vividly recall racing to Sears at 5:55 PM on a Saturday night (they closed at 6) to get a 7/8 deep socket to tighten the nuts on the new U-bolts I had to buy, though.