RearEnd noise while shifting from R to 1st
03-22-2017, 11:55 AM
#1
Advanced
Thread Starter
RearEnd noise while shifting from R to 1st
Hoping some of you can help diagnose issue I have noticed recently in my 1994 6spd LT1 90k miles - no mods.....
When shifting from Reverse to 1st gear, there is a low "groan" from the rear end of the car right before shifting out of Reverse. The noise lasts about 1 second. There is no bucking or hesitation between the gears, just the noise.
Has anyone experienced this on their C4?
Appreciate all input.
When shifting from Reverse to 1st gear, there is a low "groan" from the rear end of the car right before shifting out of Reverse. The noise lasts about 1 second. There is no bucking or hesitation between the gears, just the noise.
Has anyone experienced this on their C4?
Appreciate all input.
03-22-2017, 02:43 PM
#2
Racer
I don't know if this is the same problem, but my diff used to groan when warm, and reversing with steering lock on. It turned out to be the Limited Slip. An American Car Specialist I use over here in the UK changed the diff oil and added an additive he'd bought in the states, and within a few miles the problem was solved.
03-22-2017, 04:03 PM
#3
Instructor
It may be the ASR and/or ABS Self-testing from reverse to forward. I could be mistaken But I think there are 2 portions to ASR, one is under the hood that fudges with the throttle and another module that is right behind your seat in under what normally was a storage panel... I have heard rumors that can make some funny noises when it performs a self-test... I think it's Called the EBTCM or something like that.... One of the more technical guys can maybe explain it if I have fudged it... But that module decides what to do in a loss of traction moment.
Last edited by MrJoelieC; 03-22-2017 at 04:03 PM.
03-23-2017, 09:08 AM
#5
Melting Slicks
It may be the ASR and/or ABS Self-testing from reverse to forward. I could be mistaken But I think there are 2 portions to ASR, one is under the hood that fudges with the throttle and another module that is right behind your seat in under what normally was a storage panel... I have heard rumors that can make some funny noises when it performs a self-test... I think it's Called the EBTCM or something like that.... One of the more technical guys can maybe explain it if I have fudged it... But that module decides what to do in a loss of traction moment.
03-23-2017, 09:23 AM
#6
Advanced
Thread Starter
Ok, it ONLY happens when braking/shifting from Reverse to First (obviously at a very low/minimal low MPH) and never happens when shifting into 1st from idle.
If it is in fact the ABS/ASR self-testing, should I be concerned that it's making a noise each and every time?
If it is in fact the ABS/ASR self-testing, should I be concerned that it's making a noise each and every time?
03-23-2017, 09:29 AM
#8
Advanced
Thread Starter
03-23-2017, 06:47 PM
#10
Are you coming to a complete stop then go from R to 1st or are still rolling backwards?
Also next time try going from R to 1st then go back into R and again go into 1st and see if it does it every time.
03-24-2017, 08:34 AM
#11
Advanced
Thread Starter
I will try what you suggested this weekend if weather cooperates here in Jersey.
03-24-2017, 10:11 AM
#12
Team Owner
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St. Jude Donor '05
sounds normal to yes it will do it ea time
03-24-2017, 11:31 AM
#13
My 94 has never made this sound, so I wouldn't say it sounds normal. Without the ability for us to hear it in person this is a hard thing to say if it's normal or not.
The only sound my car my car has ever made between R/1 was a click which was remdied by replacing rear hubs and teflon washers.
I never notice the ABS test.
The only sound my car my car has ever made between R/1 was a click which was remdied by replacing rear hubs and teflon washers.
I never notice the ABS test.
03-24-2017, 11:35 AM
#14
Another thought, what about trying the reverse to first with engine off / key on? Could eliminate the running sounds and make it easier to identity exactly where the noise is from. The ABS unit is in the bin behind the drivers seat. You could open the bin and remove the sound deadener. If the noise gets considerably louder then you likely found the source.
03-24-2017, 12:26 PM
#15
Advanced
Thread Starter
Another thought, what about trying the reverse to first with engine off / key on? Could eliminate the running sounds and make it easier to identity exactly where the noise is from. The ABS unit is in the bin behind the drivers seat. You could open the bin and remove the sound deadener. If the noise gets considerably louder then you likely found the source.
03-24-2017, 01:45 PM
#16
Yes, mine is also a 6 sp.
Does the noise occur while the clutch pedal is still on the floor? If that is the case there is no torque being applied from the engine making this all the weirded. I'd confirm if it does the same at a complete stop and with the brakes applied. If it does, to me it would seem that the noise originates in the trans. What about with the engine off?
Pull the fuse for the ABS and try it out. If the noise persists you just eliminated the ABS as a source.
Start poking around the driveline. Get the car on stands, check for slop in u joints, wheel bearings, brake issues. Is there any "feeling" that occurs with the noise, a vibration, shudder, etc?
Lots of things to check and try.
Does the noise occur while the clutch pedal is still on the floor? If that is the case there is no torque being applied from the engine making this all the weirded. I'd confirm if it does the same at a complete stop and with the brakes applied. If it does, to me it would seem that the noise originates in the trans. What about with the engine off?
Pull the fuse for the ABS and try it out. If the noise persists you just eliminated the ABS as a source.
Start poking around the driveline. Get the car on stands, check for slop in u joints, wheel bearings, brake issues. Is there any "feeling" that occurs with the noise, a vibration, shudder, etc?
Lots of things to check and try.
03-24-2017, 02:01 PM
#17
Yes, mine is also a 6 sp.
Does the noise occur while the clutch pedal is still on the floor? If that is the case there is no torque being applied from the engine making this all the weirded. I'd confirm if it does the same at a complete stop and with the brakes applied. If it does, to me it would seem that the noise originates in the trans. What about with the engine off?
Pull the fuse for the ABS and try it out. If the noise persists you just eliminated the ABS as a source.
Start poking around the driveline. Get the car on stands, check for slop in u joints, wheel bearings, brake issues. Is there any "feeling" that occurs with the noise, a vibration, shudder, etc?
Lots of things to check and try.
Does the noise occur while the clutch pedal is still on the floor? If that is the case there is no torque being applied from the engine making this all the weirded. I'd confirm if it does the same at a complete stop and with the brakes applied. If it does, to me it would seem that the noise originates in the trans. What about with the engine off?
Pull the fuse for the ABS and try it out. If the noise persists you just eliminated the ABS as a source.
Start poking around the driveline. Get the car on stands, check for slop in u joints, wheel bearings, brake issues. Is there any "feeling" that occurs with the noise, a vibration, shudder, etc?
Lots of things to check and try.
03-24-2017, 02:59 PM
#18
Advanced
Thread Starter
Yes, mine is also a 6 sp.
Does the noise occur while the clutch pedal is still on the floor? If that is the case there is no torque being applied from the engine making this all the weirded. I'd confirm if it does the same at a complete stop and with the brakes applied. If it does, to me it would seem that the noise originates in the trans. What about with the engine off?
Pull the fuse for the ABS and try it out. If the noise persists you just eliminated the ABS as a source.
Start poking around the driveline. Get the car on stands, check for slop in u joints, wheel bearings, brake issues. Is there any "feeling" that occurs with the noise, a vibration, shudder, etc?
Lots of things to check and try.
Does the noise occur while the clutch pedal is still on the floor? If that is the case there is no torque being applied from the engine making this all the weirded. I'd confirm if it does the same at a complete stop and with the brakes applied. If it does, to me it would seem that the noise originates in the trans. What about with the engine off?
Pull the fuse for the ABS and try it out. If the noise persists you just eliminated the ABS as a source.
Start poking around the driveline. Get the car on stands, check for slop in u joints, wheel bearings, brake issues. Is there any "feeling" that occurs with the noise, a vibration, shudder, etc?
Lots of things to check and try.
As far as anything outside of sound....there is no shudder, no vibration, no skip, nothing. Just the whirling decompression groan....
03-24-2017, 03:13 PM
#19
Safety Car
Maybe a simple test: back up, come to a complete stop, shift to neutral, shift to 1st, move forward. See if there's noise in any of those actions. I honestly don't know where it would happen only going one way, but it could be motion related in some way.
Just a thought.
Just a thought.