switching to synthetic

[debo4x4]

I am due for a oil change soon and was thinking of switching to synthetic.  I have 35k now and have heard it was not good to switch with higher miles.  Been running 5w/30 castrol since new.  Is that just a myth or is there some truth to it?  I also am thinkng of changing my transfer fluid to the AutoTracII everyone talks about.  I still have the clunk and have tried every trick known to get it fixed, but no luck.  Every time I take it in to the dealer I get the same answer "there is no fix for reg cabs."  It seems to be worse some days than others but it drives me crazy!  The 3rd time I had it checked they lubed the yolk and that seemed to work, but ony for a few days, when I took it back again and asked to re-lube they said that it would not help anymore than the original lube.  I have been so pleased with this truck but this clunk really is getting old.

[Professor]

Myth!

 

I changed mine over to synthetic and consumption went down

 

Engine now has 350K (rebuilt @ 120 or so)

 

Go for it!

[Black02Silverado]

Myth!

 

 

Go for it!

Yes it is a myth. You can change over anytime you want.

 

[BlueRado]

With today's engines, 35K miles is barely broken in!!!  

 

Echoing earlier sentiments - myth!

 

There might be some validity to this if you were gonna put synth in my '91 lumina, which has 237K miles on it and leaks some oil now. The synth cleans so well that it can erode old seals and break up deposits that are actually helping to keep the seals from leaking and by-passing.

[2k3TahoeZ]

I'm a bit of a newbie here, but could you explain the clunk that you are getting?   Thanks.

[debo4x4]

The "clunk" you will hear so much about is most commonly referring to the slip yolk, but sometimes u-joints, depending on the case.  In my case, it is the slip yolk.  When I take my foot of the brakes after coming to a complete stop, you feel a jerk or cluck in the drivetrain.  They say it the yolk binding against the metal.  Common fixes include replacing the slip yolk, but that is only for ex-cab trucks because the yolk size is different.  You can try lubing the yolk which I have had done 2 times but the lube seems to wear off after a couple of days.  My last hope is switching transfer case fluids to the AutotracII.  I have heard mixed results about this but I am willing to try anything to get it fixed.  You can take it to the dealer but you will get the same answer I got which is "there is no fix for reg cab trucks."  They say there are no long term damaging effects by the cluck...

[2k3TahoeZ]

I've posted this before and I haven't gotten much of an answer.  My truck has jerked a couple of times, but hasn't in quite some time.  I am assuming that it was just getting broken in.  However, I do get a weird clunk when I first start driving after having the engine off.  It happens only one time after turning the engine over and putting it into drive.  I can put it in park and then back into drive and it won't clunk.  

 

It happens right around 11MPH (right around when it is going to switch into 2nd) and I can feel it in the gas pedal.  It happens in 2wd, 4Hi, and it happens even if I just leave the truck in first gear.

 

I can't get the dealership to take it seriously, so I am wondering if maybe these clunks might be related.  What do you think?

[BlueRado]

The "clunk" you will hear so much about is most commonly referring to the slip yolk, but sometimes u-joints, depending on the case.  In my case, it is the slip yolk.  When I take my foot of the brakes after coming to a complete stop, you feel a jerk or cluck in the drivetrain.  They say it the yolk binding against the metal.  Common fixes include replacing the slip yolk, but that is only for ex-cab trucks because the yolk size is different.  You can try lubing the yolk which I have had done 2 times but the lube seems to wear off after a couple of days.  My last hope is switching transfer case fluids to the AutotracII.  I have heard mixed results about this but I am willing to try anything to get it fixed.  You can take it to the dealer but you will get the same answer I got which is "there is no fix for reg cab trucks."  They say there are no long term damaging effects by the cluck...

Actually, I meant to comment on the transfer case fluid change in my previous post - my '99 rado had a really bad case of the "bump clunk", both on take off and stopping.  I had the dealer replace the older red fluid w/ the blue/green "smurf" fluid and it went away immediately.  Came back about 30K miles later, but much lighter, so I changed it myself - takes 2 qts.  It went away again, so based on my experience, it worked fine.  Assuming you have the same symptoms, it should work for you - I know it has for several other members here as well.

 

One word of caution, I don't know if the same "smurf" x-fer case fluid is used for the manual transfer case.  My '99 had the auto push-button version.  I expect your dealer will know this.

[BlueRado]

I've posted this before and I haven't gotten much of an answer.  My truck has jerked a couple of times, but hasn't in quite some time.  I am assuming that it was just getting broken in.  However, I do get a weird clunk when I first start driving after having the engine off.  It happens only one time after turning the engine over and putting it into drive.  I can put it in park and then back into drive and it won't clunk.  

 

It happens right around 11MPH (right around when it is going to switch into 2nd) and I can feel it in the gas pedal.  It happens in 2wd, 4Hi, and it happens even if I just leave the truck in first gear.

 

I can't get the dealership to take it seriously, so I am wondering if maybe these clunks might be related.  What do you think?

I'm really not sure about your issue, especially as it's a new vehicle, but I'd ask the service manager to let you drive a new hoe off the lot with him if he's so sure there's no problem with yours, and see what happens.

 

Good luck with it and keep us posted!

[WEFs99]

I agree .....it's a myth.  Changed my '90 Caravan to syn at 60k.  It stopped the lifter chatter, improved mileage and just plain ran better.  debo, I thought the '01's already have the new Autotrac fluid??  My '99 groaned on sharp turns until the new fluid was put in but that is separate from the infamous 'clunk'.

[seadoons]

My '02 Z ex-cab had the infamous clunk at stop and go, they lubricated the slip yoke and it fixed it .  My brothers did the same thing, same problem, same fix.  Mine has 32k on it, and ever since day one, when shifting from park to reverse, it just slams down into gear.  I have taken it in 3 times, this is considered normal.  They say it is nothing to do with the transmission, it is just play in the driveshaft, and no damage is being done.  Anyone else have this problem?  The next time it goes in, we (me and the service manager) are going to drive a brand new one, and if it doesn't do it, either should mine.