Rebuild-or-Replace the differential?

[dryden3]

I'm wondering what would be wisest for me to do: rebuild or replace my differential.

I believe the clutch plates are bad in mine because when I bought the car a couple of years ago, it made a grinding noise around turns and when I drained its oil, it was full of black shavings that I trust came from the clutches. After cleaning out the axle and filling with Valvoline Duralube 80w-90, it now occasionally makes a grinding noise around turns, usually after driving long distances.

Anyhow, I'm wondering if anyone here has replaced the clutch plates in their differential. If so, then where can I get them from? Would it be wiser for me to buy a whole new differential? I'd appreciate anyone's knowledge and expertice!

thanks,
John

[svocudd]

Friction Modifier

Did you add Ford's Friction modifier to the gear lube when you refilled the case?

Cudd

[richsvo]

dryden3,

Well, there are two ways to look at it...IMO. One is do you want the car to remain stock? The SVO has a 7.5 rear end. Very expensive to maintain and have rebuilt...just did mine about 6 months ago. I wanted to keep the car stock, as far as the rear end was concerned. In hindsight, I am now thinking that I would/will go with the 8.8 if there are any further problems. The reason for this is that they are more plentiful, cheaper, stronger, etc.
So, I guess what I am saying is that if you want it "stock", then stick with the 7.5, but expect problems to occur, and a rebuild somewhere down the road. If you go with the 8.8, it might be a PITA to switch out and make work, but probably worth it in the long run. It will take the mods and power that this car is capable of.
It's up to you, and remember, this is only my .02 e-cents worth!

HTH,

Rich

[SVOeric]

My 86 made the same noise in turns... -- It almost sounded like a creeking (like a rusty door opening)

I drained, refilled with mobil one synthetic, and a new bottle of friction modifier, and it hasn't made a squeek since...

[svocudd]

8.8 Swap

Rich,

I havent done the swap but i thought the 8.8 was a pretty simple swap out. Is there some sort of little detail that everyone leaves out on this swap?


Cudd

[richsvo]

Cudd,

I'm not sure myself. I have not done it yet. I will not do it, until there is another problem with my 7.5. This is the second 7.5 that I've had done, and the price difference in the rebuild alone, is worth the swap!
I wasn't trying to say that it is a difficult swap, I don't have personal knowledge of this. I was just saying that even if it were, then it would be worth it for the added strength, and availability/price of parts. That's all...

Rich

[richsvo]

Ok, guys...

I just saw this....READ.

rear end swap

There ya have it!

Rich

[Pat_in_L.A.]

Similar experience

That link richsvo posted is right on. Been there, done that.

My 84 slapper bar car puked its spider gears out just pulling out of a parking spot one day. The 8.8 T-Bird gears were 3.55 ratio versus 3.45 stock. I replaced the original axles and brakes on the 8.8 T-Bird diff housing, no problems.

The extra thing I did was put an Auburn differential in it. you can get these in the $265-$300 price range for either the 7.5 or the 8.8., so if you want to keep the original rear end housing in the car, that's still a viable move. (The old ring and pinion still looked good on the 7.5).

[Ken Potter]

A Tip After Refill

Something I always do after a refill is to find a very large flat parking lot ( local Christian school ) and do about 10 VERY slow figure 8's staying in first gear. I was told by my local guy that this is a good thing to do to help loosen up the clutch pak and to allow the modifier to get down in / mix well. Also I did an 8.8 swap in my 85 GT convert ( 4 lug drum ) and it was a breeze. I had to bend / modify the brake line bracket where it attaches to the chunk but that was all. Just wanted to throw that in...

[dryden3]

Thanks for your thoughts guys

Thanks for all of your input, guys. svocudd I didn't put the friction modifier in my rear dff because I thought having anything other than oil back there would inhibit the grinding noise but after reading SVOeric's post, maybe I should have.

To answer Rich's post, I guess I'm not sure about swapping in the 8.8" axle. I'm restoring the car now and I'd hate to install something that would hurt its value, but at the same time swapping in an 8.8" sounds like quite an improvement. Rich do you mind me asking how much it cost to rebuild your 7.5"? If I were to get a hold of an 8.8" axle, does anyone know how much less it would it cost to rebuild in comparison to a 7.5"?

The whole reason I'd thought of rebuilding my diff is I'm planning to put urethane bushings in the back, so it seemed like a good idea to rebuild as long as I've got the axle dropped down. And yes, I did read a different thread saying it's best to have one rubber bushing in each upper control arm if the rest are urethane!

[richsvo]

dryden3,

I think I paid in the $350-$400 range. That was from a friend of mine who happens to be a mechanic. He replaced everything in there except the ring and piniion (they were fine). I that is a pretty good deal, but I live in Chicago, and things can pretty expensive here sometimes. (not sure) Everyone else I called to get a quote for was asking in the $1100-$1200 range. So, of course, I went to my buddy instead. (I always check on him.)

I would think for that kind of money, you could purchase the 8.8 and have someone install it for you! I hear of people picking them up for $75 or less from the junk yard!

HTH,

Rich