Technical Ford 9 Inch - Sticking Differential

Ah, sounds like a Chebbrainwashed lol... First, do not put words in our mouths- no one in this thread ever said anything like that. I don't need to prove anything to you, not that you would listen, but I spent my childhood and career working with trucks and heavy equipment of many makes and models, and have seen plenty of very expensive stuff get boogered up by yayhoos putting the wrong lubes in stuff, and personally had to fix some of them. Put what you want in yours, as you seem to believe you are an expert- but you actually seem to just want to argue- move along, little doggie, nobody wants to play that game. And most cities have both GM and Ford dealerships, very easy for anyone to get the zero risk correct Friction Modifier in this case. Later for you lol

 

You are entitled to your opinion, I don’t pretend to know people based on the internet, however I am also entitled to give my opinion and I can respect the fact that you may not agree. Others cannot.

Also I agreed with everything you said up until it had to be Ford…I’m not sure where I was trying to argue but apologize if you feel that way.
I have better things to do then try to argue with strangers on the internet.

 

The friction modifier that Ford used came from Dana IIRC.

Most gear lubes you buy at auto supplies has friction modifier in it already... Read the label.

Type F in a Mopar? It's what I used in all of the ones I built. Mopar had in their performance manuals to add a quart of 30 w motor oil in performance built trans. I never tried it but know people that swear by it.

The condition the OP is describing is referred to as "slip-stick".

 

Sorry to stir up the GM verses Ford shit. All I know is the GM stuff worked in my posi 12 bolts, 9", and Dana 60's. Use it, don't use it.

 

Yeah I knew about the goofy 9 3/8" carrier. Turns out the axle I have is actually a 28 spline big bearing unit so, that's good enough for me. I could have sworn that I read a '71 marquis should have a small bearing axle but... the Wagon also got the upgrade police brakes so maybe the sedans did get a small bearing axle? No idea. Either way, I think I can upgrade this one as required if big power goes in.

 

I had my dirt track guys use Mobil 1 in the P/G I built for them, but they didn't run converters. Never had problem tell they got in a crash and broke the case.

 

Yeah I pulled them all apart. You can still see the cross hatch pattern in the clutch material -- although there's definitely some wear -- and they all moved smoothly. I actually don't want a super tight Traction Lok axle in this car so... I'm going to clean it up and reassemble. If I ever feel like the traction device is a limiting factor I'll put a helical gear diff in it. Mostly I just couldn't believe that an LSD would hold this hard with no torque on the pinion but I wasn't aware that Traction Lok did not apply more holding force as a function of pinion input. I'm also pretty disappointed that half of the splines of one axle are dedicated to just the LSD. Not that the 'Traction Lok" was ever exactly a hero of mine but... you know, I feel like "don't meet your heroes" is still relevant here.

 

Are you talking about adding 30W motor oil to an automatic or manual trans?

 

Interesting that one axle is longer than the other. I didn't realize this was a thing with the 9 inch. ...also another picture of this tuna boat.

 

Did you happen to mark the main caps so they go back in their exact locations?

 

Yeah I've got them marked... I suppose they may have been line bored originally.

 

Good deal, I believe your correct.

 

That reminds me of another N case I have, that is from the early days of beefed cases- it has LENCO billet caps on it. My Falcon has a 40-spline Strange setup in it, and I have another complete Mark Williams rearend with the MW cast iron case, that's also 40 spline, spool and non- gun drilled- those axles are HEAVY

 

All atf is is 30 wt oil with a red dye and a friction modifier. I had heard about the using 30 wt in a 727 never had the guts to try. But I did use type F in it and my th400. Never had a problem and it really firmed up the shifts a lot.

The GM additive for the posies plate or cone was made from whale oil. GM had to change the formula to a synthetic version in the mid 80s when their supply dried up.

Another fun fact all automatic trans fluid until the early 60s I believe was made from whale oil. Ford, GM, Chrysler, AMC, everybody! It was the only stuff that could take the heat and pressure until chemistry finally caught up.

 

ATF made in the last 30 years is about a 7.5 weight oil...Pour Straight 30 weight and ATF and you will see the difference.

 

I think it would be more accurate to say "made with whale oil as an additive", to varying degrees, and mixed with more conventional lubricants. I believe it was likely at one time to show up as an additive in A/T fluid, hypoid differential lube and manual transmission gear oils. I don't think it was ever used exclusively as an A/T fluid, but as an additive only.

https://www.straightdope.com/21344087/do-the-japanese-lubricate-new-cars-with-whale-oil

This link provides an explanation of whale oil's usage and eventual removal from the U.S. market. The details seem believable and probably factual, as far as they go.

 

A couple of things, already mentioned, the old Ford Friction modifier really stunk!
#2, drive your car in super tight circles , ten one way ten the other way. Changing the fluid would also help.
Example. I was working in a dealsrship that had quad ra tracks. A vehile came in with a drive train noise. I test drove it and to me it sounded like the gears where crawling over each other! Shop foreman checked the books. I replaced the fluid, the fluid coming out looked new! I did the ten turns thing, absolutely no noise!








Bones

 

This picture of the 2.75 pinion (next to the new 3.50) doesn't do it justice; it just looks massive when it's in the carrier.


I had intended to reuse the differential bearings but found this damage on the race. Interesting, the two differential races were different brands so I gather this isn't the first time this thing has been opened up.


And another picture of this beached whale - the vacuum leaked down after a couple days so unfortunately the headlight covers are up:


I don't have a torque wrench that goes over 150ftlbs and the manual I have calls for 175 to begin with for the pinion nut. ...so I suppose I'm waiting on even more stuff. In the mean time I'm doing the brakes. The passenger side on the car was pretty clearly new (likely 20 years ago) with almost no rust and moves very smoothly... I was able to get a passenger caliper in at an Autozone (before I had even pulled the wheels off). I've got a set of seals for the caliper itself to use on the driver's side but I also need the rubber slider grommets at the very least. If I can find a driver's side caliper (and hardware) I'll just buy it but apparently part supplies are officially drying up for these. ...realistically I should have just put some modern brakes on it but I kind of just want to drive it a bit for now.

 

Finally got it back together, all new bearings, seals, and regeared to 3.50 - I was waiting on doing the brakes. Did not replace clutches but soaked them in friction modifier after cleaning them up. It now chatters/groans instead of letting go like an explosion. Did some tight circles without much change. I imagine the lesson here was to replace the clutches. Drove about 160 miles today after three 20 minute break-in stints yesterday and this morning. The diff might be calming down a bit now but it still groans.

 

"I wouldn't soak the clutches in pure friction modifier, just get it from Ford and use the recommended ratio of modifier to oil- too much might be as bad as not enough." The lesson might be to listen more to experienced advice. They are meant to run in the proper mix of oil to modifier, not soaked with pure modifier

 

I suppose if there weren't quite a few experienced folks -- and a write up I was following -- who recommended soaking in modifier, you might have a point. For me, I've got money that says it doesn't make a nickel's worth of difference either way.

 

"It now chatters/groans instead of letting go like an explosion"
"The diff might be calming down a bit now" You might find that is works smoother the further you drive it, and more circles- because it will eventually get to the proper mix of oil and modifier in the clutches. It's gonna take quite a few turns to get to the right mix, and it will mix better after a long drive, as the oil gets warm. The plates are stationary when driving straight, so no mixing in the plates

 

I’ve never soaked the plates before installing. This is actually the first time I’ve heard of it.

 

I'm finding that the hotter the oil is, the more grabby it is. The first few drives with new gears were excessive, this morning driving down to the shop, perfectly quiet. ....I didn't count clutches or check shims... I had wanted it to be loose. But considering the previous owners installed a big tans cooler and the diff had been opened, I wouldn't be shocked to find it had been intentionally setup tight.

 

Next step: cam and intake.

...not counting lots of small steps in between.