I just installed (had installed, I didn't do it myself), a used 3:23 sure-grip unit into the T&C. I believe it's a 742 case, and it looked good on the bench.
The mechanic said lots of good things about it, and was very pleased with the difference the unit made. It got rid of some vibration issues, and generally was a good job to get done.
Now here's the rub:
If I drive on the highway for a while, say 30 minutes at 65-75 MPH, and then come off the highway for example into a parking lot, when I pull up to a stop and then have to make a sharp right or left turn at very low speeds (idle or just above), it sounds and feels like the rear end is going to vibrate itself out of the car.
I did some experimenting with it tonight...
I can go into a parking lot with the car all warm, and if I am idling with my foot off the gas, left or right turn and the car is juddering like mad at the rear.
What's going on? Only happens when the rear is warmed up. What needs to be done to fix this?
Joined: Sun Feb 26 2006, 08:46PM
Location: Kingston,Ontario
Posts: 5622
Ross,try this; With the axle warmed up, Drain the diff fluid,add new regular 80W90 in WITH TWO BOTTLES OF LIMITED SLIP CONDITIONER. I use the AC Delco bottles and they are small and cost around 7 bux each. Once the diff has been refilled with oil and conditioner,keep rear wheels off the ground. Start the car,put in drive and let it run for 10 minutes at 40MPH. Road test and chatter should go away. Monitor the operation of the Sure Grip for about 100 miles. If the chatter does not go away,the pumpkin will need to be pulled and serviced.Luckily,clutch type Sure grips are rebuildable-unlike the 489 diffs.
What is happening is when the clutches get warm,they get sticky and try to engage.If not taken care of ASAP,damage can happen to the unit . I experienced the same thing one time when I forgot to add the conditioner.
The Auburn style Sure Grip (489) and modern type limited slip diffs can use the modern type gear oils for limited slip,but the old style clutch type are a different animal. Do not use any gear oil that claims it has the additive for limited slip.They have different properties that do not work well with the clutch type Sure Grip. I tried using Royal Purple gear oil but it made the diff clunk,and noisey. Hope this helps.
<span class='smallblacktext'>[ Edited Fri Aug 20 2010, 07:12AM ]</span>
Joined: Sat Aug 19 2006, 05:03PM
Location: Ontario, Canada
Posts: 2919
I recently installed a clutch-style 3.23SG in my hardtop. added a tube of "posi-trac" gear oil additive from my local parts store, so I should be okay there. When I got it on the road, I drove straight to a parking lot and drove in circles in both directions to mix the additive thoroughly and get it between the clutch plates.
When shopping for gear oil however, I had looked at two different brands of 80W90 gear oil and both said "suitable for limited slip applications" on the bottle. I thought it was odd that the other gear oil weights on the shelf didn't state that. At the time I figured it was a good thing, since I was using it with a LSD. So Leaburn, you're saying the additives in these oils are incompatible with the clutch material? I looked online and most 80W90 gear oils claim to have limited slip additives. What oil should we be looking for?
As far as Ross's situation, why does he need to change the oil? Assuming he used "good" oil initially, couldn't he just add the limited slip additive to it to stop the chatter?
The guy said he used the "proper oil", and that there was an additive he could use, but hadn't put it in. He said it was expensive, and wasn't really required.
I can't remember the name of it, but it was like $17 a bottle, and the name started with L, like LDT or something like that. I think actually it's LSD, for Limited Sip Differential. Not sure.
Sounds like he didn't use oil compatible with Mopar clutch style suregrips, and didn't put in any additive.
I just talked to a guy and he said I should with a new sure grip, do figure 8s in a parking lot for a while. Should I do that with a used one too?
Are there lash settings that could be too tight? <span class='smallblacktext'>[ Edited Fri Aug 20 2010, 10:17AM ]</span>
Joined: Sun Feb 26 2006, 08:46PM
Location: Kingston,Ontario
Posts: 5622
The instructions I suggested are from my FSM. "...An improper lubricant can cause such noises as chatter and moan as well as scoring of the clutch plates and discs resulting in a possible failure of the unit.." Removing the oil that is in there is necessary to cure the problem. Ross,the Mopar products are fine. I recommended what works from my own experience. My point I need to be clear is the modern type gear oils-and some synthetic ones,too- that claim to be suitable for limited slip are NOT suitable for a used clutch type SG. I tried Royal Purple and my unit clunked and moaned. So I use just plain cheap old fashioned 80w90 with the conditioner I recommended. Look,I had this same problem in 2004.I thought the axles were about to snap in half. I did what the FSM said and never had the problem since--and then sold the car.
I do not recommend figure 8's on a used unit 10 minutes on the hoist--or axle stands running is more effective mixing up the fluids and getting the additive between the clutches . Just dont kick the car like Frye did......
<span class='smallblacktext'>[ Edited Fri Aug 20 2010, 12:01PM ]</span>
Joined: Thu May 01 2008, 11:15AM
Location: Chicago,IL
Posts: 2868
I have personally used the modern LSD oil with no additive in 2 clutch types (a 742 and a 741), and have never had any issues. One of them was a fresh rebuild and in my Coronet with 30x10 slicks. If it was going to grab and act nasty those tires would do it. The other was rebuilt some time ago, and was probably first run with conventional oil + additive (I don't remember for sure), but when I put it into my Fury I used the modern oil. No noise, no fuss.
I put in a whole carrier with a new Auburn cone style clutch and 3:55's. I've always added the Mopar additive such as what Ross was talking about and NO issues ever. I even used to add it to my 4 spd tranny and it cut down on the wineing that thing used to make, after it was suggested by someone. The cones don't seem to chatter like the clutches,but i would change all the fluid and start fresh like Lea suggested.