# Rust in the Rear End



## Comicazy (Feb 24, 2010)

Ok so here's the story, I bought a 1970 Tempest and drove it home this weekend. All the way home the rear end was screaming louder than the exhaust. I knew something wasn't right. So the next day i pulled the cover off, and found what looked like grey muddy water in the differential. Needless to say I was not very happy. So after dumping out and soaking up all the liquid in there, I sprayed brake cleaner to clean it up as best as I could. Now I'm noticing that there are spots of rust inside. Not like it's ate holes through the gears or anything like that. Just spots here and there. So what should I do? Is there a rust treatment that I can use? Or should I just clean it up, refill with gear oil and hope it doesn't break on me going down the road? It's not a posi unit, so I will probably replace it later anyway. But for now I just want to get it on the road. Thanks.

Just to add a bit more of my discoveries on this car. After finding the rear end in that state, I decided it would be in mine and the cars best interest to change ALL the fluids in the car. I emptied the oil, which was blacker than the racing stripes on the hood. Put a new filter on, and refilled the oil. Then dropped the trans pan and changed the filter on that and refilled with fluid. After I finish with the rear end, I'll flush out all the coolant from the radiator and engine. The exhaust has a leak coming from the right collector, and go figure. The headers dump into a collector that immediately gets downsized to either 2.5 or 2.25. The mufflers look reletively new, but look like they would be the stock replacement for a mid 90's buick lesabre or some other V6 car. All that has got to go ASAP. Looks like I have my work cut out for me on this one. You'll bee seeing a lot more of me on here.

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## Rukee (Feb 8, 2007)

I'd just refill the rear end and then when you go to a posi unit like an Auburn carrier grab yourself an installation kit with the new pinion and carrier bearings and shims. You should probably replace the rear wheel bearings at the same time. If it continues to be excessively loud after just the fluid change you might wanna consider that posi upgrade sooner then later.

If the rear was under water the front might have been as well. You may want to pull the front wheel bearing apart and inspect and repack/replace as needed.


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## 66tempestGT (Nov 28, 2009)

i would put the real thick stuff in it. 85-140 i think. something 140 anyway. you might get lucky. more than likely the bearings are rusty too. that will be the noise, not so much the gears. you can put some bearings in it and keep rolling.


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## Rukee (Feb 8, 2007)

Yea, but if your going to press the carrier bearings off and on you might as well press them onto the new carrier as you occasionally wreck the bearings pressing them off.


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## geeteeohguy (Feb 2, 2008)

Really good advice Rukee suggested: Water got in the diff somehow, and usually, that's by being submerged. Flood car?? Grease all front bearings and suspension fittings, check for water damage elsewhere, and address it. If it still howls after new gear oil, it will need new gears, etc. Better off just to can the whole unit and buy a replacement assembly from a forum member, craigslist, or a wrecking yard. One that HASN'T been under water.


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## Comicazy (Feb 24, 2010)

Hmm, I never thought about the car being submerged in water. The rest of the car looks pretty good. A little paint bubbling. But the quarter panels are solid as well as the rest of the under carraige. I'll take a closer look at the rear of the car with the wheels off tonight.

Ok, so quick question then, Is there a fill bolt in the diff? Cuz my cover doesn't have a hole to pour fluid into. If not, how do you put the right amount of fluid in? And how much is the right amount? Thanks again.

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## Rukee (Feb 8, 2007)

There is a 3/8" square drive plug facing forward, remove the plug and fill till it comes out the hole.


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## Comicazy (Feb 24, 2010)

Ok, I have 1 Qt of fluid in my garage. Is that going to be enough or am I going to have to get some more? I still have to get a new seal for the cover so I want to get it at the same time if I need more.

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## Rukee (Feb 8, 2007)

grab 2 more quarts.


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## Comicazy (Feb 24, 2010)

Well a little update. The parts store didn't have a diff seal in stock, so I have to wait to finish that up until my order comes in for that. 
I started taking apart the rear tail lights because most of them don't work. I found a lot of corrosion in most of the tail light housings. I have 4 replacement housings that I need to wire in. And I need to find new reverse light housings. I also found a lot of debris and junk that suggests that the car may have had its rear end stuck in a swamp or something. But it looks like for the most part, the guy tried to fix it up as best as he could, he just couldn't get the little things done. 
The trunk is painted with that splatter looking paint. Might be something like rhino liner. So really the only things that really need some work are the tail lights and the rear end. As far as exterior mechanical stuff goes. 
Oh yea, and the rear end is a 12 bolt housing. Is that Normal? And is a posi unit the one where you can spin only one wheel by hand when its jacked up? Cuz thats what mine does.
To be continued....

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## Rukee (Feb 8, 2007)

You could just use some silicone sealant to seal the rear cover on.

A posi unit will turn both wheels the same direction when you turn just one and the tranny is in neutral and the rear is jacked up.


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## Comicazy (Feb 24, 2010)

Yea I thought about doing it with silicone, but I've never liked messing with that stuff.
Ok, so what does that make my unit? Is that the 'open' Diff that I've read about?

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## Rukee (Feb 8, 2007)

Yes, it's an open rear. But the good news is is it's a 12 bolt. Much stronger then the 10 bolt so when you go to the posi unti your gunna be about bullet proof. :cheers



After cleaning the cover and housing just run a bead of silicone on the cover and let it sit for about 15 minutes before puttting it on. Then if possable let it sit overnight before refilling.


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## Comicazy (Feb 24, 2010)

Well I finally got the rear end put back together and put oil in it. I filled it to the top then spun the tires a bit to get it worked into the axle tubes, then filled it again. I was going to keep doing this, but then I noticed that the oil was dripping from the from of the differential. Go figure, I have a leak in that front seal. How much does that usually cost to get that fixed? Is it something a simple mechanic like myself could do? Or do I need like a press or some other complicated tools?

Also, I tried the method of putting one tire on the ground and spinning the wheel to see what gear ratio I had. I put it in neutral, then spun the wheel and had my wife count how many times it rotated while I watched the driveshaft. I counted 13 revolutions of the driveshaft to 10 of the tire. Is it just me or does that not sound right? That would make it like 1.3:1 right? I have to be missing something. HELP! Thanks.

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## 66tempestGT (Nov 28, 2009)

i would have looked at the carrier and the numbers on the gears or at least counted the teeth while the cover was off. why put it back together then try to figure all this stuff out.


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## Rukee (Feb 8, 2007)

Comicazy said:


> Well I finally got the rear end put back together and put oil in it. I filled it to the top then spun the tires a bit to get it worked into the axle tubes, then filled it again. I was going to keep doing this, but then I noticed that the oil was dripping from the from of the differential. Go figure, I have a leak in that front seal. How much does that usually cost to get that fixed? Is it something a simple mechanic like myself could do? Or do I need like a press or some other complicated tools?
> 
> Also, I tried the method of putting one tire on the ground and spinning the wheel to see what gear ratio I had. I put it in neutral, then spun the wheel and had my wife count how many times it rotated while I watched the driveshaft. I counted 13 revolutions of the driveshaft to 10 of the tire. Is it just me or does that not sound right? That would make it like 1.3:1 right? I have to be missing something. HELP! Thanks.
> 
> Comic


Dividing the 10 by 5 to get 2 you would get 2.6 to the drive shaft giving you a 2.6(4)? gear ratio?


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## 66tempestGT (Nov 28, 2009)

Rukee said:


> Dividing the 10 by 5 to get 2 you would get 2.6 to the drive shaft giving you a 2.6(4)? gear ratio?


confused:confused


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## Rukee (Feb 8, 2007)

Sure you can, you spin the one wheel twice and count the # of drive shaft turns and that's your gear ratio. :cheers
So dividing the 10 turns by 5 to get 2 and dividing the 13 by 5 you get 2.6(4) gear ratio.


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## 66tempestGT (Nov 28, 2009)

sorry, didnt see your reply. thought about it some more and changed my mind.:cheers


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## 68greengoat (Sep 15, 2005)

Rukee said:


> Sure you can, you spin the one wheel twice and count the # of drive shaft turns and that's your gear ratio. :cheers
> So dividing the 10 turns by 5 to get 2 and dividing the 13 by 5 you get 2.6(4) gear ratio.


Now that's thinking with your dipstick..... Jimmy.


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## Comicazy (Feb 24, 2010)

Ok, so now that we've got the gear ratio figured out and out of the way. How about the problem with my leaking seal. Any thoughts on that?


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## jetstang (Nov 5, 2008)

Comicazy said:


> Ok, so now that we've got the gear ratio figured out and out of the way. How about the problem with my leaking seal. Any thoughts on that?


Thats not hard, just take the pinion nut off the U joint yoke, pull the yoke off, pry the seal out and replace. Ensure everything is clean so it doesn't eat your new seal up. Nothing to press off or on, definatelly not a hard job.
Oh, I have the 10 bolt out of my 70 laying behind my shed if you end up needing a rear end. It's open carrier with 2.73s.


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## Comicazy (Feb 24, 2010)

Ok, is there any special things I should look at while I have that off. Anything I need to be worried about messing up? Thanks.


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## Rukee (Feb 8, 2007)

Before you remove the yoke nut, try to move the yoke up and down left to right. There should be no movement. If there is the new seal may not seal either.


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## Comicazy (Feb 24, 2010)

Ok, so if it does move, does that mean I need a new yoke? Or new universal joint(s)? Both? I'm fairly new to working on driveshafts and differentails. I usually stay in the engine compartment or the interior.


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## Rukee (Feb 8, 2007)

After you remove the driveshaft and before the yoke, if the yoke moves around then the pinion bearings would be bad, or at least need to be tightened up.


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## geeteeohguy (Feb 2, 2008)

Comicarazy, I recommend you have a mechanic replace your pinion seal. The crush on the crush sleeve is critical to rear end set-up, and it's easy to mess it up when re-installing the pinion nut if you have never done it before. If nothing else, mark the pinion nut BEFORE you loosen it, and count the threads on the pinion shaft. Install the nut in EXACTLY the same position as it was.


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## Comicazy (Feb 24, 2010)

That's the kind of stuff I was wondering about. I had read somewhere about crush sleeves and similar things to look for. 
I was thinking of maybe just waiting a month or so to buy a new set of posi gears from summit and have them installed at the same time. Would that be an advisable option. I don't need to drive the car anytime soon. I could just work on rewiring the tail lights while I wait to do that. I was thinking 3.73 gears.


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## Rukee (Feb 8, 2007)

What tranny do you have? and what size tires are you going to be running?


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## Comicazy (Feb 24, 2010)

Tranny is TH350. Tires will probably be stock size. Maybe a little bit bigger. Not sure about that yet.

I looked at the rear end while on lunch today. A LOT of fluid has come out of it. And I wrote down the numbers that were on it. Tell me if any of them make sense. Looking from the back, on the right side of the housing in the middle it has the numbers 12345 samped upside down. Then on the lower part of the right side it has D 8 2. On the lower left side it has C 2. Anywhere else I should be looking for numbers? Thanks

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## Comicazy (Feb 24, 2010)

Looked for the numbers again. Found them on the front of the passengers side tube.

KD C 104 1

I believe it is from a 71 and up car. I can't find the KD but I believe the rest translates that it was made in Buffalo on April 14th Day shift. Anybody got more info?

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