3.73's installed today, and...

Bill9000 · Jul 3, 2005

all I can say about performance is WOW, my car DID have 2.73's it was stamped on the pinion. the change to 3.73 is great.

I have a few dumb questions:

I installed the gears myself, set backlash within tolerance, etc. (don't try this at home in the backyard!) it was a difficult thing in a shop with a lift and all tools, impacts, etc.

they feel great, 'cept I have a whine at speeds of over 60, and only when accellerating, or letting off it. it's not a real loud whine, but it's definitely there... here's my questions: hopefully someone has the right answer.

1) if my experience is correct, they should not make ANY whine at all, is this true?

2) what is the correct gear oil for the diff. I used 80w90 thats what NAPA's book supposedly called for. do I have the wrong type in?

3) friction additive? is this something that's necessary??? and of so, would it cause a slight whine y not having it?

I've only put 30 miles on the car since install for break in, so I don't believe I have damaged anything, but I do think I may have something wrong with the oil.

thanks in advance!

97gtblue · Jul 3, 2005

i did my gears and they whine a little, and i drove 25 miles and the shops i called said they wont touch it cause i put to many miles on them already..i need try chaining the gear oil

Joel's98GT · Jul 3, 2005

I would double check the pinion depth. I had a whine from 55-65 when i got mine done, took it back to the guy and s said yes it was 4 thousandths off, it has quit whining and has a couple thousand miles on it now

Mossberg · Jul 3, 2005

How can you hear any whine with your exhaust combo?

Bill9000 · Jul 3, 2005

Mossberg said:
How can you hear any whine with your exhaust combo?

well I was worried 'bout the same thing, but if I barely touch the gas, I can hear the noice, and if I let off it I can hear it. if I push in the clutch and let it coast, no noise at all.

would that friction" additive stuff be important????

I triple-quadruple checked the pinion I really can't be taking it back apart now!!!

I'm hoping I just have the wrong gear oil in it.

merc123 · Jul 3, 2005

I had mine done at Ford. No whine (at least I can't hear it anyway)

Bill9000 · Jul 3, 2005

merc123 said:
I had mine done at Ford. No whine (at least I can't hear it anyway)

I woulda had a specialty shop do it, but they wanted $350 just for labor, parts not included, I figured 1 day of my time is worth way less than $350 to me!

That $350 would probably buy a nice lift off cowl hood or something

I just don't think I necessarily did my homework well enough to know that it has the right kinda gear oil.

east_sidaz40 · Jul 3, 2005

i had mine done at ford too. there is definatly a whine. not too bad though. I used 70W140 oil which should be correct. plus the friction additive. when i turn right i hear a "metal rubbing sound" they told me they need to replace the diffrential clutch

Bill9000 · Jul 3, 2005

my whine is ALMOST not audible over my exhaust, it's pretty minor, and it doesnt bother me, I just want to make sure that it's ok, and the rear end's gonna live. Ford told me now that the 80w90 is right for it, and that it should have the friction additive. (I didnt do the additive) I'm wondering if not having that would make it whine a little bit

Bill9000 · Jul 3, 2005

another quick thought: is it possible that the aftermarket gears are just going to have a very slight whine? I'm ok with that as long as it's not gonna scatter on me or something!

hotmustang331 · Jul 3, 2005

Mine doesnt really have any more whine than stock with my 3.73s. We didnt change the shim...we just swapped carrier spacers. the other day i heard a SLIGHT whine, but even stock they make a slight noise. Before that I really have never heard anything. It has been VERY hot though, so the oil was prolly a little thin. I used 70W140 royalpurple oil...it already had the posi additive included in it. Change to the 70W140 and you probably wont hear anything...that oil is too thin. The owners manual tell you that it calls for 70W140, those outparts people can never get anything right LOL.

mrvax · Jul 3, 2005

I did the same swap but had some hi-speed vibration. I got the aluminum d/s and all the vibration went away.

Bill9000 · Jul 3, 2005

hotmustang331 said:
Mine doesnt really have any more whine than stock with my 3.73s. We didnt change the shim...we just swapped carrier spacers. the other day i heard a SLIGHT whine, but even stock they make a slight noise. Before that I really have never heard anything. It has been VERY hot though, so the oil was prolly a little thin. I used 70W140 royalpurple oil...it already had the posi additive included in it. Change to the 70W140 and you probably wont hear anything...that oil is too thin. The owners manual tell you that it calls for 70W140, those outparts people can never get anything right LOL.

so if I have 80w90 in now, and I drain it, and add 70w140, that could stop a slight whine?

dollarbill · Jul 3, 2005

hotmustang331 said:
Mine doesnt really have any more whine than stock with my 3.73s. We didnt change the shim...we just swapped carrier spacers. the other day i heard a SLIGHT whine, but even stock they make a slight noise. Before that I really have never heard anything. It has been VERY hot though, so the oil was prolly a little thin. I used 70W140 royalpurple oil...it already had the posi additive included in it. Change to the 70W140 and you probably wont hear anything...that oil is too thin. The owners manual tell you that it calls for 70W140, those outparts people can never get anything right LOL.

I agree with this dude 100%. Change the fuild and add the Royal Purple. The side of the bottle says it already contains the friction modifier, and yes it could be causing the whine.

FalconGuy016 · Jul 3, 2005

I think I hear this same kind of whine with my stock gears. I hope they didnt mess that up too at the factory...

BaconBits · Jul 3, 2005

You HAVE to put in a friction additive when you do gears. Some gear oil has it built in, but that's rare. Without it you may get chatter and lockups especially around turns. My guess the whine is coming from the gear oil being to thin. And make sure you put full synthetic gear oil in as well. Yeah, that stuff stinks something fierce, and is a pain in the ass to get the smell out of your garage, but changing the stuff you have in there now will really make a difference down the road. I'd go with Royal Purple or Mobile 1.

Bill9000 · Jul 3, 2005

BaconBits said:
You HAVE to put in a friction additive when you do gears. Some gear oil has it built in, but that's rare. Without it you may get chatter and lockups especially around turns. My guess the whine is coming from the gear oil being to thin. And make sure you put full synthetic gear oil in as well. Yeah, that stuff stinks something fierce, and is a pain in the ass to get the smell out of your garage, but changing the stuff you have in there now will really make a difference down the road. I'd go with Royal Purple or Mobile 1.

thank you, I will certainly try this. I like this answer a whole lot better than pulling it back apart and resetting pinion depth (which I SWORE was right)

I'll get some of this before moving the car again!

Joel's98GT · Jul 4, 2005

RP oil has friction modifier already in it, i'm pretty sure redline does as well.

Azarello · Jul 4, 2005

east_sidaz40 said:
i had mine done at ford too. there is definatly a whine. not too bad though. I used 70W140 oil which should be correct. plus the friction additive. when i turn right i hear a "metal rubbing sound" they told me they need to replace the diffrential clutch

hey off topic, How do you like that Mac Cai? I still got mine in the box, is it worth it or should I take it back?

east_sidaz40 · Jul 4, 2005

Azarello said:
hey off topic, How do you like that Mac Cai? I still got mine in the box, is it worth it or should I take it back?

It nice , for show , and sounds nice when shifting gears also . you wont really notice any gains. But i will tell you this.....the instal is a PITA

3.73's installed today, and...

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