TheRonTom3

iTrader: (5)

Ok so I installed my 4.27 rear welded diff last week and there is a quite odd noise coming from my rear end. I know what shot bearings sound like and that is a loud humm or a whine. I also know that if the gear lashing is off that can make a grinding or ticking sound which this is not either.

The sound I am getting is almost like a wooshing/hissing air sound. easiest way yo describe the sound is cup your hand over your mouth and blow air through your teeth, blow more air as speed increases. Literally like there was something in the differential pushing air out the breather as speed increases it gets louder but its barely and it is only audible from inside the car. Could it be something to do with normal operation sound traveling up through my now solid bushings?

any ideas?

5sp_jzz30

iTrader: (2)

lashed too tight and it will be be more like grinding. lashed too loose and it will whine.

did you have the same differential removed, welded, and reinstalled? if its a different diff then you should definitely check your backlash.

BTW whats the word on that fender we talked about? did you figure out how much you want for it?

TheRonTom3

iTrader: (5)

It is a different whole pumkin entirely. The Carrier/diff was never removed from the pumpkin when it was welded so everything should still be 100% factory spec. After the welding and cleaning it out I inspeced to make sure operation was smooth and this unit sounded better than the one I took out of my car.

As for the fender the drivers side was the fine one the passengers side i shot, flipped it over and it has some surface rust and I forgot its the one that was primed. I'll get a pic for you today

BigWaveSC

iTrader: (5)

a welded diff with solid bushings is going to be loud but I dont know about a whine or air noise...

rwdanthony

iTrader: (53)

you sure you didnt not out one of the body plugs under the carriage? like under th erear seats or spare? is your interior gutted?

i also have a welded diff with solid bushings, i thought it was normal to get that humming sound cause the drivetrain becomes more solid, the solid bushings also transfer the sound/vibrations to the cassis.

if air is really coming out of the diff covers breather, double check your diff fluid level. the only thing i can think off, if not, its normal...

TheRonTom3

iTrader: (5)

Diff fluid should be perfect I put 1.5 quarts of full synthetic in.

It probably is normal noise with the more soild rear end, I have full interior. It just odd my car with the windows up sounds like a turbo car now.

Like i said the sounds is 100% NOT a hum or wine, I have had to replace bearings in wheel hub and such before so i know that sound. This is just a weird sound so thats why Im scratching my head on this one.

I figure im just going to let it go if it gets louder I'll start to worry. I feel like I should have taken my own advice here, this is a reason you don't do two mods at once. lol

good2go

iTrader: (6)

Taking a long shot here, but you don't by any chance have a Walbro fuel pump do you? They're known for making similar noise. It got so bad, I thought it was the stereo amp hissing until I finally checked it out. Finally ended up stuffing a blanket on top of the fuel tank to muffle the sound. Way better, but still audible if you're listening for it.

Like I said, just a long shot.

TheRonTom3

iTrader: (5)

Haha it was a long shot. Thanks for the help man I unfortunately do not have a walboro. Pretty sure its a normal operation sound that most people dont here cause they have their windows down or the radio or the HVAC on. I just happen to hear it one day because it was raining and my ipod was dead so I had the windows up and no radio or HVAC on.

gsta127

iTrader: (1)

did you notice any acceleration gains from swapping to 4.27 gearing?

5sp_jzz30

iTrader: (2)

definitely a worthwhile upgrade for stock engine people.

i swapped from my stock 5sp(4.08) to a sc300 auto(4.27) and drifting was so much more fun. first 2 gears were a bit shorter but definitely felt better.

currently i have a sc400(pre 98 so its a 3.97 or something like that)...absolutely freaking terrible. if i was on any type of turbo setup the longer gears would definitely help but on stock motor its just sucks. it feels that the gearing falls in between gears all the time. going in 4th seems to make the rpm spike too much and going in 5th makes it feel like its bogging.

so far i have tried all the sc diff ratio options. only thing left is to finish my turbo swap on that sc400 3.97 diff and see how it does.

TheRonTom3

iTrader: (5)

Its not neck breaking or anything like that but like 5sp_jzz30 said it is a lot more fun. Its like the car makes power everywhere rather than just in the high rpms. Most of the bogging has gone away.

I will also confirm that on my 97 the speedometer is now WAY off. I'm not 100% sure but I'd say close to +10-15 mph at 70