F-series diff knocking

**Draven** · 13-12-2005, 07:01 PM

My brother's 1j cressy has developed a nasty knocking sound in the diff. According to him, he was under heady load and heard a loud "clunk" from the diff, and now we have a speed dependant knock coming from the arse of the car.. sounds much like worn CV/wheel bearings do.

My first guess is that he might have a diff bearing on the way out, and thus it could fairly easily be fixed by dropping the diff off to a specialist to replace all bearings.

Any alternate opinions?

**oldcorollas** · 13-12-2005, 09:39 PM

Originally Posted by Draven

My brother's 1j cressy has developed a nasty knocking sound in the diff. According to him, he was under heady load and heard a loud "clunk" from the diff, and now we have a speed dependant knock coming from the arse of the car.. sounds much like worn CV/wheel bearings do.

My first guess is that he might have a diff bearing on the way out, and thus it could fairly easily be fixed by dropping the diff off to a specialist to replace all bearings.

Any alternate opinions?

i once had a tooth off the spider gears come astray and get wedged between the crown and the carrier... such that the pinion contacted the tooth each time it came around... car still drove ok, but the clunking was terrible...

i would suggest drop it out and see what broke.. if all the teeth are intact, then check bearings for roughness and go from there?

oh and see if you can correlate the speed of the sound with the speed of the wheels (ie one knock per wheel rotation) = crown damage, or 3.?? knocks per wheel revolution is pinion damage....
for bearing damage, they usually spin at half shaft speed, but it depends on what failed.

you could even be scientific about it

wheel diameter = X number of turns per minute at 20km/hr.... then pinion = Y number of turns at 20km/hr....
bearings for crown = 0.5X and bearings for pinion = 0.5Y

then measure clunks per minute at same speed....

i would be very interested to see how this goes as i'm probably just talking shit

but if it works in practice... it's a good theory

Cya, Stewart

**BlackSupra** · 13-12-2005, 09:42 PM

It may seem too simple, but check the bolts in the tailshaft. A loose one will give you a speed varying clunking noise which peak harmonic reasonance is about 108km/h.

**Norbie** · 14-12-2005, 01:00 AM

Originally Posted by Draven

According to him, he was under heady load

Nice euphemism... I'm going to start using that one.

**Draven** · 14-12-2005, 07:53 AM

well ok, if we're going to be straight about it he was foot to the floor stepping out going round a corner... in other words driving it normally

Thanks for that stu, my other thought was the possibility of throwing a tooth off the spider gears and having it end up somewhere it shouldn't be. will check tailshaft bolts today to rule that one out.

**TheStitt** · 14-12-2005, 03:04 PM

I had F series, Spit/destroy the centre pin of the spider gears which moved out asnd into the crown wheel making a nice mess of this.

this was cause by multiple single spinners my diff bloke said.