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Where is the fill hole on the rear diff

R

Rodimus_Prime

Well-Known Member
is the fill hole on the rear diff cover? There's like a rubber thing on the cover I thought it was supposed to be somewhere along the top of the diff?
 
Rodimus_Prime said:
is the fill hole on the rear diff cover? There's like a rubber thing on the cover I thought it was supposed to be somewhere along the top of the diff?
Click to expand...

Yeah, It's that rubber thing on the cover. pry it out with a flat screw driver or similar tool. The diff should be full to the bottom edge of the hole in the cover.
 
Did you add limited slip additive? If not you will need to stop at a local GM dealer and pick up a bottle (it'll be small like 4 fl oz and cost about $8).
 
Yea I added the gm posi stuff first then it took about 2 qts or so of the 75w90, good thing is everything looked great in there, pretty much like new, no metal bits, shavings, or teeth missing, old oil smelled terrible and sort of baby shit green.

When I first got the car I was told there was some leaking from the diff cover but I never addressed it. There was barely over a quart that came out into the drain pan. While I'm sure thats a problem I still have the issue at highway speed where the entire drivetrain feels like its vibrating. I'm not sure if its wheels out of balance, or wheel bearings, I'm running out of stuff to replace.

This was also my first good look under the rear of the car, good lord the stock suspension pieces are junk. Thin ass U shaped control arms and that piece that goes from side to side over top the axle.
 
Rodimus_Prime said:
Yea I added the gm posi stuff first then it took about 2 qts or so of the 75w90, good thing is everything looked great in there, pretty much like new, no metal bits, shavings, or teeth missing, old oil smelled terrible and sort of baby shit green.

When I first got the car I was told there was some leaking from the diff cover but I never addressed it. There was barely over a quart that came out into the drain pan. While I'm sure thats a problem I still have the issue at highway speed where the entire drivetrain feels like its vibrating. I'm not sure if its wheels out of balance, or wheel bearings, I'm running out of stuff to replace.

This was also my first good look under the rear of the car, good lord the stock suspension pieces are junk. Thin ass U shaped control arms and that piece that goes from side to side over top the axle.
Click to expand...

You bought a car and didn't check the fluids? First thing you do when you get a new car...

Fluid smelled because it probably was burned...goodluck with that rear!
 
It was something I kinda put off, but its addressed now and everything in there looked real good, couldnt see really any wear
 
You can't see wear on the posi unit and your trans fluid was low too. Is your oil low? Coolant? Brake fluid? Power steering fluid?

Have Nick help you if you aren't capable.

Jason
 
Quiky One said:
You bought a car and didn't check the fluids? First thing you do when you get a new car...

Fluid smelled because it probably was burned...goodluck with that rear!
Click to expand...

The fluid smelled because it's diff fluid, right up there with ATF with the worst smelling fluids that are impossible to get rid of if you get it on your skin.

Rodimus_Prime said:
Yea I added the gm posi stuff first then it took about 2 qts or so of the 75w90, good thing is everything looked great in there, pretty much like new, no metal bits, shavings, or teeth missing, old oil smelled terrible and sort of baby shit green.

When I first got the car I was told there was some leaking from the diff cover but I never addressed it. There was barely over a quart that came out into the drain pan. While I'm sure thats a problem I still have the issue at highway speed where the entire drivetrain feels like its vibrating. I'm not sure if its wheels out of balance, or wheel bearings, I'm running out of stuff to replace.

This was also my first good look under the rear of the car, good lord the stock suspension pieces are junk. Thin ass U shaped control arms and that piece that goes from side to side over top the axle.
Click to expand...


While the lower control arms and panard bar look cheap and flimsy they're not that bad for straight line, but they'll flex side to side. BMR makes some great tubular replacements that just bolt right in, you can find them lightly used all the time on the different forums. They're both actually the exact some parts for 4th Gens so you can look on ls1tech.com and some of the 4th gen sites if you want to go that route.

As for the vibration, can you feel it in the steering wheel? Does it do it when you have a consistant load on it, say going from 65 to 80 slowly over the course of a mile or two? Vibrations are hard to diagnose over the internet since they're really one of those things you have to feel and hear to help provide guidance of where to look.
 
I was looking at the spohn stuff, I'd love to just dump 2k and get the K-member, lower control arms, panhard bar and torque arm.

The vibes are the same whether im on or off the gas, though the noises increase with speed. I can feel it in the wheel, the seats, the floor, the whole car pretty much.

I was hoping that maybe a potential cause of this was the rear end but now thats done it hasnt changed anything.
 
I don't know what the other limited slip additives smell like but if it is anything the stuff that Ford uses it is one of the nastiest smelling things I have ever smelled. Everyone told me to wear gloves when I added it and I'm glad I did. It takes weeks to get rid of that smell. Left my drain pan sit outside for a month.
 
I had that same issue where the car would shake and it ended up being a bad spark plug if I remember correctly? I know it was something stupid and simple. That was on #733 and I had the convertor replaced again since that was what it felt like. (lucky Jimmy did it for free, Jimmy's Transmission is excellent!) It still did it after the new convertor was replaced, then Jimmy says "Hey have you checked the plugs latley, cause that will cause it to do that too" lol

Live and learn and that is why I change the plugs every year. Plugs, Fuel Filter, Oil&Filter and PVC every year in the spring time.

Rodimus, just a thought, if you are diving at a speed where the car is shaking try and take it out of gear, does it still shake?
 
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Its not really a shaking, and yea it does make the noise whether the car is in gear or not. Its just road noise and vibration, feels like im on the worlds hardest rubber tires. Kinda hard to explain in writing. Just seems like it should be smoother and quieter at highway speed. When your saying the converter, are you referring to the tq converter?

Ah I know what its like, you know when they scrape all the asphalt off a road with those grater things when they are doing repaving and the road is all rough, the noise it makes while driving over it at higher speed, thats kinda what it sounds like.
 
Yes, the Tourge Convertor.

Maybe your tires are cupped. Bad shocks or struts can cause that. IDK, try different tires if you think that it is just noisey road noise.
 
im going to take it to one of the local places and have them balance the wheels and align it, even if thats not the problem im sure it wont hurt since it prob hasnt been done for at least many years
 
apparently its still leaking :(

so I ordered a new gasket, and im going to use that this time, the cover did look kinda chewed up must have been hitting something at some point years ago, main thing thats a problem right now is finding a new plastic cap for the diff cover for where you fill it, old one is hard and brittle

would this work http://www.justdifferentials.com/index.php?main_page=index&cPath=28_69_454

looks like it will but what are those other screws for in the middle, says something about bearing caps? and it holds more fluid ?

anyone have this?
 
I used a Felpro gasket and blue RTV. No leaks.

Yes, that cover will work. Very, very nice piece. Run it on the GN.

Jason
 
On both sides of the gasket or just one with the RTV?

As far as that cover, what are those two big bolts in the middle for, do they bolt to something on the gears inside or something?
 
Rodimus_Prime said:
On both sides of the gasket or just one with the RTV?

As far as that cover, what are those two big bolts in the middle for, do they bolt to something on the gears inside or something?
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Just one side. In fact, the rear end on my truck doens't have a gasket. RTV only. No issues.

The bolts in the middle are a girdle. You snug them down the 8 ft/lbs to keep pressure on the gears. Supposed to help the longevity. :D
 
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