2020-B1-1

Author Topic: Limited Slip problem  (Read 913 times)

Pontiac_SE

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Limited Slip problem
« on: September 07, 2019, 05:41:41 AM »
I have just put together a rear end, the parts I have used is old but good GM parts.
Original GM limited slip and a 2:41 gear, axles are nice original.. all new bearings and preload and backlash is spot on.

When I drive it is quiet in the rear but after a while it will make a cracking noise when I drive slow.
I guess it is the limited slip that is making the noise, I have 80w90 that already has LS additive then I have added two 4oz with Kendall LS additive and it is still making noise not much but still.

The limited slip comes from another T/A -77 low mileage and didn’t have this problem, but it have laying in a box for 2 years if that matters.
What should I do?
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

hakitup

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Re: Limited Slip problem
« Reply #1 on: September 07, 2019, 09:49:17 AM »
Noise happens driving straight or turning? If it is the LS clutches, it will only happen during a turn. My pops when I first get off the freeway after a long drive I added friction modifier and it helped but didn’t stop it completely. I have new clutch plates that have an aggressive hex pattern not like the swirly originals.

Tom H
"I don't know what you call it, I only know the sound it makes when it lies!!"

Pontiac_SE

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Re: Limited Slip problem
« Reply #2 on: September 07, 2019, 10:26:58 AM »
Only when I turn but it doesn’t need much turning before it makes noise.
The clutch plates is original from 1977 in this one.
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

highway star

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Re: Limited Slip problem
« Reply #3 on: September 07, 2019, 06:28:39 PM »
Only 4 oz. of additive is required. And don't use Valvoline, it's recycled oil & smells terrible like old oil.
I just ordered Castrol gear oil, it has a "sweet" smell.

hakitup

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Re: Limited Slip problem
« Reply #4 on: September 07, 2019, 08:59:58 PM »
The 74 Pontiac bulletins dealer book I bought at the Nats addresses the posi. It said to add the friction modifier the drive the car in a figure eight to work in the oil. I thought it was kind of funny because I was having an issue with it. Before I added the modifier it sounded terrible, kind of like it was coming apart.

Tom H
"I don't know what you call it, I only know the sound it makes when it lies!!"

Pontiac_SE

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Re: Limited Slip problem
« Reply #5 on: September 08, 2019, 09:40:32 AM »
I started with GULF 80W90 LS and it sounded terrible then I added 4oz Kendall additive, after that it got little better.
After a few days I added one 4oz more and it got a lot better but still I can hear it from time to time and it is really annoying.
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Fbird

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Re: Limited Slip problem
« Reply #6 on: September 11, 2019, 06:39:56 AM »
after adding the friction modifier did you do a few "figure eights" to work it in the clutches? Normal driving will take weeks to "work in". a few tight figure eights and you should be good.
67 Firebird
1980 Turbo TA (injected 400 now :) )

Pontiac_SE

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Re: Limited Slip problem
« Reply #7 on: September 11, 2019, 09:25:26 AM »
Yes I tried the figure eight, didn’t help.
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Fbird

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Re: Limited Slip problem
« Reply #8 on: September 11, 2019, 11:25:52 AM »
going to need to determine the "break-away" torque of your clutch pack assembly. you may need to disassemble and clean EVERYTHING....but that sux.

http://www.premierwestgears.com/RebuildLimitedSlipDifferentials.html

good read.
67 Firebird
1980 Turbo TA (injected 400 now :) )

Pontiac_SE

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Re: Limited Slip problem
« Reply #9 on: September 11, 2019, 12:44:53 PM »
Thank you I will check the break-away torque.
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Pontiac_SE

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Re: Limited Slip problem
« Reply #10 on: September 14, 2019, 03:12:34 AM »
Well, just checked the torque and it is around 60ft-lb which is very low.. I am really beginning to hate this car....
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Fbird

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Re: Limited Slip problem
« Reply #11 on: September 15, 2019, 06:08:16 AM »
at 60 lbs  this is sounding like NOT THE clutches issue.....

don't take this one wrong.....
you check the lug nuts?
67 Firebird
1980 Turbo TA (injected 400 now :) )

Pontiac_SE

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Re: Limited Slip problem
« Reply #12 on: September 15, 2019, 06:29:18 AM »
Don’t worry I won’t take it wrong, I actually checked them and everything else..
The only thing that’s not been changed is the brake drums, it’s the original to the car.

About 5 years ago I had to change the brake shoes because the wheel cylinder leaked, beginning to think that the drums are “contaminated” or something.

I think I will buy all rear brake parts new and replace it..
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

firebirdparts

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Re: Limited Slip problem
« Reply #13 on: September 15, 2019, 07:01:19 AM »
60 ft-lb is actually high according to the shop manual.
I want to be like Paul Kenny when I grow up
Joe Bays
1977 Y82 4-speed (red interior)
1978 Skybird 350
1978 Redbird 305
1979 Redbird 301 4-speed
1992 Lincoln Mark VII LSC/SE (red)
1970 Datsun Pickup
1953 Chevy pickup (converted 4x4)
1988 T-bird Turbo Coupe

Pontiac_SE

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Re: Limited Slip problem
« Reply #14 on: September 15, 2019, 07:47:36 AM »
I did take a look in the service manual and I cannot find the break away torque just rotating torque and it says at least 35 ft-lb, I have approx 45 ft-lb.
What torque should the break away be?
« Last Edit: September 15, 2019, 07:50:05 AM by Pontiac_SE »
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Re: Limited Slip problem
« Reply #14 on: September 15, 2019, 07:47:36 AM »


2020-B1-8


Fbird

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Re: Limited Slip problem
« Reply #15 on: September 16, 2019, 06:39:07 AM »
going from MEMORY here....like 35 yrs ago....best I recall was 70-140 lbs BREAK AWAY.....
The hard part of measuring this is having the proper tools/adapter to do it as it must be measured per the CL of axle rotation. as shown here
https://www.musclecardiy.com/performance/how-to-rebuild-factory-limited-slip-differentials/

obviously different bolt patterns would require different "adapters"...
again IIRC there were 2 "s" springs available from GM one is like 190 lb and the other was like 300 lbs which gave you about a 60 lb INCREASE in breakaway torque.
67 Firebird
1980 Turbo TA (injected 400 now :) )

Pontiac_SE

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Re: Limited Slip problem
« Reply #16 on: September 16, 2019, 08:51:58 AM »
I did use an adapter so it was centered when I checked the the torque.
I have bought all rear brake parts so I will change them and if that doesn’t help I will take the diff apart..
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Fbird

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Re: Limited Slip problem
« Reply #17 on: September 16, 2019, 01:29:09 PM »
some confuse HOW to test this.
Hope the brakes solve the issue otherwise that sux.
67 Firebird
1980 Turbo TA (injected 400 now :) )

Pontiac_SE

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Re: Limited Slip problem
« Reply #18 on: September 28, 2019, 09:43:46 AM »
All new brakes in the rear and no change, have made several test runs and done a lot of “8” and it still makes a lot of noise. (Sometimes it is all quiet)
When I drive slow and it makes the noise I can almost see the left rear wheel “vibrating”...

I am out of ideas now.
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Pontiac_SE

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Re: Limited Slip problem
« Reply #19 on: September 29, 2019, 02:40:06 AM »
I have checked everything I think and the noise is coming from inside the diff, I just don’t know what... this is actually the third diff that is making this noise.
I have changed the housing, driveshafts, brakes, gears, bearings and u joints....

I know it is really difficult to guess what’s the problem is so I appreciate all the help I can get.
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Fbird

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Re: Limited Slip problem
« Reply #20 on: September 29, 2019, 06:36:30 AM »
I have checked everything I think and the noise is coming from inside the diff, I just don’t know what... this is actually the third diff that is making this noise.
I have changed the housing, driveshafts, brakes, gears, bearings and u joints....

I know it is really difficult to guess what’s the problem is so I appreciate all the help I can get.

So lets regroup a minute here, just to double check our vocabulary and all the pieces that HAVE BEEN CHANGED:
the entire rear axle housing.
the axles
the brakes
differential (what the ring gear bolts to..since we are talking individual components) ie known to have been good previously
Gears
u-joints
driveshaft
_________

Your comment of "this is the third DIFF ...." concerns me that you are either extremely unlucky or you are miss-diagnosing where the issue is located.
please explain DIFF (as we are referring specifically to COMPONENTS)
DIFF .... in its common term would imply the ENTIRE differential housing ASSEMBLY unbolted from the leafs completely sealed.
DIFF ... in specific terms is the differential carrier located within the housing assembly ONLY.

67 Firebird
1980 Turbo TA (injected 400 now :) )

Pontiac_SE

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Re: Limited Slip problem
« Reply #21 on: September 29, 2019, 10:23:02 AM »
Sorry.. “Diff”: differential (carrier)

4 year ago: Right of nowhere my original rear end starts making noise (3:23 posi) took it apart and changed all bearings, it didn’t help.

Took it apart again and changed the gears to a Richmond set and Richmond Excell axles shafts with all new bearings again... making noise again.

Took it apart again and changed the complete differential to a used one (2:56 posi) that only had 9000km, changed to another new set of Richmond axles shafts.. was now quiet a couple of months then it came back (the noise)

Now I bought a used complete housing with axles and a 2:41 open differential, I put the 2:41 gears on a used posi which has about 10000km on it..
I put in all new bearings and a set of good used GM axles shafts.
I still have the noise.

So yes all parts you listed has been changed some parts several times..

Note that both used  differentials did not making noise in previous cars.

It is a crunching, popping noise and when it “pops” you can see the left wheel “pop” if you know what i mean.
When I added more limited slip additive it did changed a little but I already have 8oz in it now..

It is hard to explain in English because it is not my first language.

Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Fbird

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Re: Limited Slip problem
« Reply #22 on: September 30, 2019, 09:25:27 AM »
gonna have to ponder on this a little....
67 Firebird
1980 Turbo TA (injected 400 now :) )

Fbird

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Re: Limited Slip problem
« Reply #23 on: October 02, 2019, 06:41:01 AM »
i would assume when changing the differential carriers that they were "assembled" meaning had their OWN spider gears all ready installed?

Something remain constant is all this mess. Not sure WHAT ... but something has remained.. PROVIDING the rearend is making the SAME noise/issue in ALL configurations. The "wheel pop" sounds and looks EXACTLY like clutch bite...but with only 60 lb breakaway...i would find that difficult to blame! (not ruled OUT but just not likely).

1st i would recommend quit changing parts. ( i get it..) the more things you change at this point...the harder it is to find the culprit. For instance: put new axles, bearings, gears, clutches,brake....
still have A problem. Multiple changes at 1 time means EVERYTHING is NOW suspect in the problem. Since at this point you are clearly about to burn the car down. Back-up re-read/re-evaluate all the work you have done chasing this gremlin to determine what parts are good, whats bad, what the common issues have been and the common parts.

Time to go back to step 1.
FORGET ALL PREVIOUS HISTORY....doen't matter at this point, heres what you got NOW
problem is?
symptoms  showing?  (is it only the left wheel? or is that the only one YOU can see opening up your door while MAKING it happen?)
Then start at the brakes and really evaluate  each piece to ensure it is assemble and functioning as designed,
U-joint, open cover LOOK, catch some oil as it drains in a coffee filter (to evaluate with flashlight), LOOK assembly, at each gear, feel the rotation....the less you find the deeper you gotta go.

best I can do.
67 Firebird
1980 Turbo TA (injected 400 now :) )

Pontiac_SE

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Re: Limited Slip problem
« Reply #24 on: October 02, 2019, 10:13:10 PM »
Thank you, I will do so.

I don’t know if both wheel “pops” as I only have seen the left through the door.

As I mentioned before I have changed the u-joints and every time I have change the rear axle I did check the u-joint.... in the rear.
Yesterday I took the driveshaft off the car and I can feel that two of the bearings on the front u-joint not running smoothly, I really don’t know if this could be the problem but I have to change it before I can look further.


Spider gears has not been changed.
If it doesn’t help I will do as you suggested and exam every part.

I will come back with results.

Thanks again.
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Pontiac_SE

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Re: Limited Slip problem
« Reply #25 on: October 04, 2019, 12:54:46 PM »
Well.... that did fix the problem.... really really feeling so stupid right now  :?

This particular u-joint I replaced two years ago when I put a new yoke on the driveshaft.
I really didn’t think about checking this..
Firebird -93 (sold)
Firebird -94 (sold)
Firebird Esprit -71 (sold)
Trans Am -79 Y84 (sold)
Trans Am -77 Y82 (finally got one)

Ford5of5

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Re: Limited Slip problem
« Reply #26 on: October 04, 2019, 07:56:47 PM »
In my opinion, TAC is a feeling stupid safe zone. Everyone on here has done something stupid, they just will not admit to it!  :lol:

Here's something stupid that I did to my car: 


I've also destroyed umpteen oil pan gaskets because I didn't know that even if your 1/2" torque wrench says it goes down to 15 ft lbs, it doesn't. :mad:

Fbird

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Re: Limited Slip problem
« Reply #27 on: October 06, 2019, 07:21:24 AM »
In my opinion, TAC is a feeling stupid safe zone. Everyone on here has done something stupid, they just will not admit to it!  :lol:

Here's something stupid that I did to my car: 


I've also destroyed umpteen oil pan gaskets because I didn't know that even if your 1/2" torque wrench says it goes down to 15 ft lbs, it doesn't. :mad:

Well.....until a moment ago there was only 1 person who knew you did something stupid....lol
67 Firebird
1980 Turbo TA (injected 400 now :) )

Ford5of5

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Re: Limited Slip problem
« Reply #28 on: October 06, 2019, 11:56:30 AM »
I freely broadcast my stupidity for 2 reasons. First, so someone else doesn't have to learn the stupid/hard way. Secondly, so that others know that I'm stupid and let me know that I'm about to do something stupid.  :lol:
« Last Edit: October 06, 2019, 12:01:43 PM by Ford5of5 »

Re: Limited Slip problem
« Reply #28 on: October 06, 2019, 11:56:30 AM »
You can help support TAC!

 



2020-B1-4