my differential

[tomls1]

there's a possibility that my differential is the cause of a clunking noise coming from the rear of my car. i'm planning on changing the fluid and i'm curious as to what people are using on their c5s (gm standard, redline etc) . i understand that there's a posi additive that i need to use when i change the fluid, does this go for the aftermarket fluids too? i'd love to hear some opinions.

thanks,

tom

 

[c4c5specialist]

Hi there,
That is interesting. I would suggest that you elaborate on the noise, and give us a better description.
I suggest only using the GM part numbers listed in your owners manual, with the friction modifier.
But, I would ask for more information.
Allthebest, c4c5

 

[tomls1]

c4c5, thanks for the reply. here's a little elaboration.

the noise is evident when i pull away at normal driving speeds and sometimes when i slow down. it's somewhat sublte (in that i don't hear it if the radio's up). the sound is a mixture of a clunk and a cluck and it only happens once, that is, until i stop and start again...i guess it kinda toggles with forward and backward motions.:confused

originally, i was thinking that it may be u-joints, but i hear those aren't very often a problem in c5's. any help is greatly appreciated.

hopefully this description helps rather than confuses more.

 

[c4c5specialist]

Hi there,
I would suggest a different course of action here.
If you are handy, I would obtain a 34mm axle socket, and remove each of the rear axle nuts, with the tires mounted and on the ground.
Spray a little rust pentrant on the splines of the shaft, that protrude through the hub. Then retorque the nut to 118 ft lbs.
Let us know if the noise goes away.
I believe it will.
Allthebest, c4c5

 

[tomls1]

c4c5,

thanks, i'll give it a try. would you believe i have a 32mm and a 36mm, but no 34mm. i'll pick one up and give it a try this weekend (maybe tomorrow night if i get a chance).

i'll post the results as soon as i do it.

thanks,

tom:cool

 

[tomls1]

c4c5...you rock!!!

last night i picked up a 34mm socket and did exactly what you said. the noise seems to be gone now. i drove it around last night and to work this morning is stop and go traffic and i haven't heard it yet.

question...why did this fix the noise. was it the re-torqueing (one side was really tight when i first removed the nuts), or spraying the rust penetrant on the splines. i'm really curious.

thanks again.

tom

 

[c4c5specialist]

Hi there,
Moisture buildup inside the spline to hub area, creates the noise, due to rust buildup on the spline contact points within.
When you spray the pentrant, you are lubricating the splines, and stopping the noise.
And you should really not have a reoccurance.
Allthebest, c4c5

 

[tomls1]

thanks again, your posts are an invaluable resource on this site.

tom:cool

 

[vettered91]

c4c5specialist,

I since the last 45 days I have been with almost every shop in town, dealers too, they have changed the 2 drivers side u joints and they have check-remove every nut, and the clunk noice stills the same it comes from the hub area every time I change from P to R or from R to D.

If this thing works for me you deserve a bottle of the best Tequila from me. The Tequila Town is 30 minutes from here!

See you,

George