4L60E 95 Vette Recent Rebuild 3K Miles Chirping When Fluid Below 120F
07-31-2007, 10:12 PM
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4L60E 95 Vette Recent Rebuild 3K Miles Chirping When Fluid Below 120F OK, Frank from Performabuilt was nice enough to help me out here online with my slipping converter problem and now my tranny works just fine.
Only problem to speak of is this chirping metalic noise that almost sounds like a bad alternator bearing....sorry it is the tranny, as I have a new alternator
This damned chirping started over a month ago...I rebuilt the tranny this past winter and posted photos of my experience.
Strange thing is that after the car runs for about 4-5 minutes and the tranny fluid gets above 120F the chirping sound goes away completely and doesn't return until after the tranny sits and cools down again.
Fluid is fine..Royal Purple MaxATF
If I have to I'll live with it, but I just wondered if the experts have ever heard of this symptom before.
BTW, I recently tested the line pressure with my gauge and tech1A and found it was almost pegged at 300 psi at the low ma range. I therefore have lowered the pressure by readjusting the pcs about 1/2 turn counterclockwise....pressure is within spec now. I was able to produce the chirp when ramping up the pcs when it was adjusted too high, but now it still persists only when cold.
Also, please note that a prior tranny builder had done this tweak and that is what probably cause me to have to rebuild the tranny as it blew out the forward and 3-4 clutch retainer lands in the input drum
Only problem to speak of is this chirping metalic noise that almost sounds like a bad alternator bearing....sorry it is the tranny, as I have a new alternator
This damned chirping started over a month ago...I rebuilt the tranny this past winter and posted photos of my experience.
Strange thing is that after the car runs for about 4-5 minutes and the tranny fluid gets above 120F the chirping sound goes away completely and doesn't return until after the tranny sits and cools down again.
Fluid is fine..Royal Purple MaxATF
If I have to I'll live with it, but I just wondered if the experts have ever heard of this symptom before.
BTW, I recently tested the line pressure with my gauge and tech1A and found it was almost pegged at 300 psi at the low ma range. I therefore have lowered the pressure by readjusting the pcs about 1/2 turn counterclockwise....pressure is within spec now. I was able to produce the chirp when ramping up the pcs when it was adjusted too high, but now it still persists only when cold.
Also, please note that a prior tranny builder had done this tweak and that is what probably cause me to have to rebuild the tranny as it blew out the forward and 3-4 clutch retainer lands in the input drum
Last edited by redvet99; 07-31-2007 at 10:28 PM.
08-01-2007, 07:20 AM
#2
What is your max line pressure in forward? Make sure that it is between 200-230psi. I like to see 210-220. It sounds like you are having a pressure noise that is coming out of the pump. Hopefully you have not damaged that pump yet. But if it has to come out again I'm sure your getting good at it. Good luck. Vince
08-01-2007, 09:17 AM
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If I remember right at 850 (hotcam) rpm idle my line pressure is 75 psi in all gears except reverse where boost yields about 90 psi.
Using my Vetronix Tech1a, to exercise the PCS, at the lowest ma reading the pressure at idle is around 225 psi. I adjusted the pcs to attain the spec readings in the GM service manual.
I originally was figuring it might be a bearing, however, I agree it's probabaly a pressure squeal, and that's why I'm going to live with it for now.
Everything works just great otherwise......
Using my Vetronix Tech1a, to exercise the PCS, at the lowest ma reading the pressure at idle is around 225 psi. I adjusted the pcs to attain the spec readings in the GM service manual.
I originally was figuring it might be a bearing, however, I agree it's probabaly a pressure squeal, and that's why I'm going to live with it for now.
Everything works just great otherwise......
Last edited by redvet99; 08-01-2007 at 09:49 AM.
08-01-2007, 11:14 AM
#4
One of the problems in these units is that builders tweak the PCS screw in an attempt to produce higher pressure for better shift feel and piston clamping force. That is not the best idea for this unit. There are even some shift kits on the market that recommend this proceedure. But it can be taken way too far.
It can and will put too much stress on the pump causing it to fail prematurely. As Vince stated there may be some damage done inside the pump at the slider and the vanes and this could be the source of your noise. Certainy you have taken the stress off of it by moving the adjustment back, but time will tell.
Excessive line pressure is not required to turn one of these units into a workhorse!
g
It can and will put too much stress on the pump causing it to fail prematurely. As Vince stated there may be some damage done inside the pump at the slider and the vanes and this could be the source of your noise. Certainy you have taken the stress off of it by moving the adjustment back, but time will tell.
Excessive line pressure is not required to turn one of these units into a workhorse!
g
08-01-2007, 03:56 PM
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Yup, agreed....I know first hand, high line pressure tends to break things, at least now I know what the cause of my original problems some 6 months ago were...too bad I didn't discover this earlier as I rebuilt the pump myself with a new GM front pump half, refinished rear half, new 13 vane high performance rotor, vanes and slide, hardened rings, single HD2 slide spring and 0.50 oversize boost valve...was a thing of beauty when I put it together
Thanks for the quick reply
Thanks for the quick reply
08-01-2007, 05:23 PM
#6
Hey sorry you still have that nosie just holler if you need any help when you get ready to try and find the issue, Sounds like you have a handle on the pesure , I think originally someone was a bit overzealous as mentioned in turning it up. This is a reason we use new PCS because you never know who and how many times its may have been turned up I know alot of people just servicing trans have been known to do that to just give it a little better feel. Glad your lockup issue is solved though and again glad I could help.
Originally Posted by redvet99
Yup, agreed....I know first hand, high line pressure tends to break things, at least now I know what the cause of my original problems some 6 months ago were...too bad I didn't discover this earlier as I rebuilt the pump myself with a new GM front pump half, refinished rear half, new 13 vane high performance rotor, vanes and slide, hardened rings, single HD2 slide spring and 0.50 oversize boost valve...was a thing of beauty when I put it together
Thanks for the quick reply
Thanks for the quick reply
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08-01-2007, 08:54 PM
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Thanks again Frank.
It was over 95 today in Manhattan, and in an hour of bumper to bumper traffic with my air on and inside a cool 68F my tranny stayed a cool 195F
On the highway it came down to 186F within 15 minutes or so
It was over 95 today in Manhattan, and in an hour of bumper to bumper traffic with my air on and inside a cool 68F my tranny stayed a cool 195F
On the highway it came down to 186F within 15 minutes or so
