Whoa! So I CAN replace just the diff parts, rather than the whole rear end/axle?! I thought it was all one part. If I am gonna replace the drums etc, should I then go ahead and do the whole rear end like some are suggesting, or can I do this piece-meal and get 'er on the road sooner/cheaper rather than later/costlier?

I need to order a shop manual.

t

 

The guilotine clamp is not attached to the shock, if you look at the pictures closely. The shock is attached to the lower spring plate. The clamp is only holding the lower bracket for the coil, which is not factory, like number dummy said. As for the rear diff, I'd open it, and see what is actually wrong with it. Could be easier and cheaper to fix it as opposed to replacing the entire rear axle assembly. If the actual carrier is good, and the cross pin, side gears, spiders, etc. are good, and it only needs a ring and pinion, those are not expensive. A good Richmond set can be had for fairly cheap. A decision as to the final intended purpose of the truck will effect the choice of gear ratio, and differential type, as much as any other factor. If it's a performance oriented goal, then a 9" can get VERY expensive converting to posi, with the right gears, and finding the right nodular carrier. If it's a more towards stock, than rebuilding the current diff could prove more cost effective in both finances, and time. If it's a nice street cruiser, an 8.8 would be a very good choice, as they are less expensive to build than a 9", and are far more plentiful.

 

The parts for a dana 41 are hard to get, so keeping it original means fighting that now and in the future. The choices of gear ratios are less (in the 48, you had 2 options - neither of which got you over 55 mph).

If you want to do quicker and open up more options later, a swap is the way to go. You can finish a swap in a weekend, whereas dropping it, disassemble, reassemble, and reinstall probably will add a day.

Pro / Con list
1) speed - the swap will be faster
2) cost - breakeven, hard to find parts + new brakes might run you as much as junk yard full beam
3) future - the swap will give you a lot more options (add a locker from JCWhitney for $500 if you want)
4) safety - automatic adjuster brakes are no more or less safe than manual if attended to, but if you are a neglectful driver then modern brakes probably are better.

I went with a swap because of all 4 reasons, I seriously considered the ford 8.8 as well. I've kept the dana 41 in case I want to sell it as original, just a day of wrenching and it could walk out the door the same way it came in.

And who knows, if I ever have issues with the 9", I might go to a 8.8 with discs. (or if I do the mustang II IFS swap and get discs up front)

I would say the biggest driving issue for me was time, I want to start enjoying my truck (it sat for 8 years while I had no money), so the swap was faster, got me a drivable road gear and better fuel economy, got me better brakes, opened more options.

 

If you want to piece it together to get on the road sooner and save money then that is what I would do. Just make sure that brakes and the like are operating correctly first so that you and your family don't get hurt.

As far as replacing the whole assembly that just depends on cost, parts availability and what your ultimate goal is with the truck. Heck there are enough guys upgrading on here all the time that you can probably get a good used stocker rearend for darn near free to get you by for now and then figure out which way you want to go later.

 

Another thing I just thought to suggest since you are just starting out, and self proclaimed "not a car guy" if you go the swap route and go junkyard be sure what you get from the yard is in good shape, don't trust the tag, or assume everything is perfect shape. Things end up in the junkyard for a reason - mine had a smashed front nose clip and a worn through brake line. Spin the wheel and count the number of driveshaft turns - does it match the tag, if you get a locker block one wheel and see if the locker works right, inspect all parts of the brakes - any missing hardware, etc. Be sure to drain the old diff oil out and replace (manual specifies 100weight summer, 90 weight winter I believe (manual is with the truck at the shop right now so not sure). No sense taking your "missing one tooth" rear end out to put in one with two teeth missing :P

 

It also doesn't hurt to get the warranty from the wrecking yard... Sometimes it's good to get... I paid an extra $150 for a 1 year warranty on my daughters rear end...

 

That is so tempting!!

 

Can't take you anywhere. Typical fighter pilot.

 

Gentlemen...and lorolr ...thanks very much for all the advice. Between this thread and the other active one I have on here, I have a much better understanding of the whole rear end replacement issue. I have read the articles you've sent me to etc. and I pretty much "get it" now. I am still unsure about whether or not I will need to do/hire out welding or not, but I will get that figured out. I still have some questions though...

What gear ratio do I want in order to make the truck freeway-worthy? Higher or lower?

How do I know if the differential and associated gear ratio is right for my transmission?

How difficult is it to make sure the pinion angle/ drive shaft angle / tranny output shaft angle all match and are correct? I am concerned that if I am inaccurate I will screw things up.

Has anyone done business with "Total Cost Involved Engineering" out of So Cal? I am considering buying a rolling chassis from them. Here is text from the email they sent me after a phone call...
"Tyler, as I mentioned, the chassis is boxed front to rear, is 8 inches tall for additional rigidity, has the nut-zerts welded into place to eliminate through bolts and provide ease of assembly. Also, the brake booster, master cylinder and pedal assembly along with the brake lines are included and installed. Rear end is brand new from Currie featuring a Nodular case, huge 31 spline axles, big bearing and brakes. Our chassis features 11” disc brakes, and I will add them to the rear at no cost, along with a free front sway bar and upgrade the brake lines to stainless steel."

They want $8300 plus tax for the chassis and $500 shipping. Can anybody vouch for the quality of their chassis and how good a deal this is?

Again, thanks for all your help!

 

I have a TCI chassis. I like the metal works part of it. Everything fit perfectly. The down-side is that it's been sitting in my garage for about 26 months(never been driven) and virtually every rubber part has dry rotted and needs replaced. The other down side was after spending $800 for delivery to my home, the chassis showed up at the warehouse and they called me to come and get it. I explained to them that I paid for home delivery and I want it brought to my home at which point they say that they can't get a "big truck" up in my neighborhood. So I called TCI and my vendor explaining that full length school buses come up here 4 times a day and that my neighbor drives his semi and trailer home ever day. They refuse to deliver, and I refuse to hire somebody to go and get what I paid to have delivered. At this point, TCI couldn't care less. Finally, the trucking company put it onto one of their box trucks and deliverd it. So, before you buy, I'd find out who the trucking company is and make sure they're willing to deliver to your property instead of leaving you holding the bag. That little fiasco cost me about 3 weeks of my vacation (I'm a teacher) when I could have been working on my truck. I bought it through Tim's Hot Rods on the west coast ( Tim's Hot Rods ) who I'd highly recommend as he kept pushing from his end and didn't leave me stranded like TCI.

 

Gear ratio depends on several things, but simply a gear in the range of 3.50 works for either OD on non-OD trans, tall 16" wheels/tires or shorter 15" combo. I have combinations of all those in different trucks and in my opinion 3.50 is about the best all around setup for whatever you might throw at it.

Drop to 3.00 and you'll notice take off lagging some but will run with lower rpms and better mileage on the hwy. Go above 4.00 and you get neck-snapping takeoffs, but will max out quicker on the freeway.

That said, my favorite is 3.50 with an OD trans. Even 3.25 w/ OD could work for me cause I'm old enough that leaving black strips on the pavement behind me has lost much of it's appeal. (except in the Shelby : ))

If you have an OD trans multiply your rear end number by the percentage output to see what it comes out to. Most OD's are in the neighborhood of .70 final output. So 3.50 x .7 = 2.45, which is a great freeway final ratio.

All non-OD's are 1:1 ratio so the rear ratio isn't affected 3.50 is 3.50.

Driveline: Buy a $10 magnetic angle indicator at your local parts store and you won't mess up your driveline angles. You want your trans output shaft to be the same angle (but opposite direction) as your pinion input shaft.

If those two are close to the same angle you don't have to worry about your driveshaft. In practice, if you get the trans and pinion within a degree or two of each other it will work. Most trans sit about 5 or 6 deg down angle. Position your pinion 5 or 6 deg up and you're good to go.

The "angle" of the driveshaft doesn't matter - it can run up, down or side to side. What you need to match is the movement of the U joints.

If your truck is raised significantly, 9 deg of angle will start destroying Ujoints on a regular basis. fwiw

 

Before doing anything, why not pull the rear cover and investigate this "missing tooth". That sounds funny to me. Honestly, I've never heard of a tooth breaking off either a ring or pinion in anything like normal use (drag racing maybe). It costs you nothing to open it up and see if there really is a problem, or if the PO heard a bad U-joint or wheel bearing and drew the wrong conclusion.

 

Thanks for the info. Sounds like customer service follow-through was a bit lacking. That is too bad. You mentioned the rubber parts dry rotting. Is that because it has been sitting for 2+ years, or are you suggesting that the rubber part were of inferior quality and not a good buy? Would they have dry rotted if you had gotten your tuck assembled and on the road sooner?

Thanks,
Tyler

 

OK, thanks for that explanation mtflat....

So a lower gear ratio is better for driving at higher speeds, like on the freeway, and the higher gear ratio is better for acceleration, short races etc? Since this is for my son, I think the lower option is better. And we'll get better gas mileage, right?

I am still not sure what transmission I have in the truck, but I am betting it does not have overdrive. It is an automatic that was put in back in the 60s or 70s. So a 3.25 or 3.5 would be ok with that?

I guess I am misunderstanding something here about the gear ratio thing. Let's say you have a 4.00 differential. So for every 4 turns of the transmission output shaft/drive shaft, you get 1 turn of the wheels, right?

Wouldn't that mean that the LOWER gear ratio would give you quicker acceleration? If you have a 3.00 differential, it would take only 3 turns of the drive shaft to get 1 turn of the wheels. Theoretically, if you took it all the way down to a 1.00 differential, every turn of the drive shaft would give you a turn of the wheels.

But apparently it is the opposite. You say a 4.00 diff gives you the break neck acceleration, but tops out sooner, and the 3.25 diff gives you slower acceleration but a higher top end speed.

So what am I missing? I must be doing the math backwards but I think that's because I am misunderstanding the gear ratio concept of differentials. Can anyone straighten me out?

Thanks guys.

t

 

This from my other "Bought it!" thread, but is better suited here...

Quote:
Originally Posted by 51PanelMan View Post
Stick with what mtflat said in his post to your other thread. Also, read this article, 1948 through 1960 Ford F-1 and F-100 Rear Axle (differential) Swaps .: Articles. It'll explain everything to you.

I read the article and it is very informative. I understand a lot more now. But a couple of questions it brought up....

1. The axle width is measured from axle flange to axle flange...so what is an "axle flange"? How do I identify that part? Can anyone post a picture of an axle flange? Or even better, a picture of a tape measure stretched across from axle flange to axle flange?

2. I can't remember what my other question(s) was...they say the memory is the second thing to go...and I can't remember what the first is....Oh yeah....now I remember (my other question, that is). Are there any other articles here on exactly HOW to do a rear end swap? Step by step instructions? The link in the above quote/post talks all about choosing a new rear end, but is not really a how-to-install-it article.

3. Will the axle width screw up wheel/tire clearance on the fenders. How close is close enough?

Thanks!

T