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Amount of Limited Slip Differential additive to use

Ecomike

Ecomike

NAXJA# 2091
NAXJA Member
Location
MilkyWay Galaxy
I have a dillema. Haynes manual says to use 2 oz or 5 oz of limitted slip diffy fluid additive, depending on the rear end and whether it has track lock....but does not say how much to use on Dana 44 rear ends. Mine is an '87 Dana 44, rear end with NP 242 transfer case.

I have a 7 oz tube of TransX brand limited slip diffy fluid additive, and the Trans X package says to add all 7 ozs to the rear end.

What should I do? What is the risk involved of over or under using this additive on a fresh change out of diffy fluid? I am using GL-5, 1 quart of 85-140 WT plus 1 quart of 80-90 WT, non-synthetic Lucas brand, gear oil as they were out of 85-140 WT when I went back for a second quart. I have the trailer towing package and I am in a hot climate.
 
Also the 2 quarts of Lucas gear oil I have show "Exceeds service level GL-5, ....PG-2 limited Slip!

Does this mean the Lucas already has the limited slip additive in it? If so should add any more?
 
Add the whole tube. The exact percentage isn't that critical. I don't care what the gear lube bottle says, I added friction modifier to my D35 limited slip.
 
I just found this on oil medic, does not answer my question, but it was informative!

"A performance area not addressed by industry specifications is limited slip. Because of hardware differences among the various limited-slip differentials, no standard industry-wide test is available to evaluate a lubricant's ability to prevent chatter in this application. Lubricant requirements, therefore, are based on performance in an individual manufacturer's test rig or vehicle. (Lubrizol)"
 
I use GM friction enhancer (modifier?) and limited slip gear oil.
The only down side I can see for using 85-140 is it's hard to find, gets really stiff in cold weather and likely affects mileage a little.
I do a bit of high speed driving (100 plus MPH, Germany :) ) and always opt for the 140 when I can find it. I'm running 90 wt now.
Limited slips don't last forever, the one in my 96 is getting tired, just an opinion, but until it needs a rebuild I don't think a little extra friction enhancer is going to hurt much.
My 96 is beyond the mileage I'd normality expect the carrier bearings to be replaced, so it has held up rather well. The friction enhancers don't seem to have hurt anything.
The rebuild kit for the OEM limited slip is kind of pricey.
The use of the GM friction enhancer is a hold over from my Chevy days, it seems to work noticeably better on older limited slips IMO.
Last opinion, limited slips shed some ablative material, which can't be good for bearings. I exceed the HD maintenance schedule for most all of my drivetrain services.
 
Last edited:
Ecomike said:
" Lubricant requirements are based on performance in an individual manufacturer's test rig or vehicle. "
Click to expand...

It says keep adding friction modifier until the clutch disks stop chattering.
 
8Mud said:
I use GM friction enhancer (modifier?) and limited slip gear oil.
The only down side I can see for using 85-140 is it's hard to find, gets really stiff in cold weather and likely affects mileage a little.
I do a bit of high speed driving (100 plus MPH, Germany :) ) and always opt for the 140 when I can find it. I'm running 90 wt now.
Limited slips don't last forever, the one in my 96 is getting tired, just an opinion, but until it needs a rebuild I don't think a little extra friction enhancer is going to hurt much.
My 96 is beyond the mileage I'd normality expect the carrier bearings to be replaced, so it has held up rather well. The friction enhancers don't seem to have hurt anything.
The rebuild kit for the OEM limited slip is kind of pricey.
The use of the GM friction enhancer is a hold over from my Chevy days, it seems to work noticeably better on older limited slips IMO.
Last opinion, limited slips shed some ablative material, which can't be good for bearings. I exceed the HD maintenance schedule for most all of my drivetrain services.
Click to expand...

Ok now you've done it, just what the hell does this additive really do? Is there a variety of these additives? Does it increase friction, or increase slip, thus reducing friction? The TransX additive I have here says it reduces chatter, clatter and gear noise in LSD differentials!

Oh, and by the way, I got started on this fluid change, rear end inspection because of the clatter marble noise I was hearing on hard right turns under power at less than 10 mph.
 
IIRC, the Lucas does not require an additional LSD additive.(It has been awhile since I used it though, it used to say on the back of the bottle)

But the recommended amount of additive is 6.5%, on 3 pints of fluid in the Dana 44, its 3.12 oz.

Its probably not a suprise that I use Severe Gear 75w-140 though......
 
I found some more interesting discussion here:

http://www.toyotanation.com/forum/archive/index.php/t-196715.html

Thanks for the rapid response guys!!!!! Much appreciated! :yelclap:

From what I have read it seems to increase the slippage on turns, thus being a lube enhacer, allowing the clutches to slip more, not less! So it does not increase the friction, but reduces it, correct?
 
Is it only 3 pints? Mine was not full and it looks like 4 pints that I drained out?

w_howey said:
IIRC, the Lucas does not require an additional LSD additive.(It has been awhile since I used it though, it used to say on the back of the bottle)

But the recommended amount of additive is 6.5%, on 3 pints of fluid in the Dana 44, its 3.12 oz.

Its probably not a suprise that I use Severe Gear 75w-140 though......
Click to expand...
 
Ecomike said:
I found some more interesting discussion here:

http://www.toyotanation.com/forum/archive/index.php/t-196715.html

Thanks for the rapid response guys!!!!! Much appreciated! :yelclap:

From what I have read it seems to increase the slippage on turns, thus being a lube enhacer, allowing the clutches to slip more, not less! So it does not increase the friction, but reduces it, correct?
Click to expand...


Yes... Its the reason that properly formulated synthetic fluids don't require it....
 
Ecomike said:
Is it only 3 pints? Mine was not full and it looks like 4 pints that I drained out?
Click to expand...

The FSM shows 3 pints, and my AMSOIL book shows 3 pints for the D-44.

But you would still fit it to the bottom of the fill plug.

If 4 pints is what actually what fits. Then you would need 4.16 oz. of LSD additive.
 
Ecomike said:
Ok now you've done it, just what the hell does this additive really do? Is there a variety of these additives? Does it increase friction, or increase slip, thus reducing friction? The TransX additive I have here says it reduces chatter, clatter and gear noise in LSD differentials!

Oh, and by the way, I got started on this fluid change, rear end inspection because of the clatter marble noise I was hearing on hard right turns under power at less than 10 mph.
Click to expand...

Maybe my terminology is a leftover from my street racing days. Friction modifier is a better term. What the bottle actually says is Goodwrench limited slip differential lubricant additive, 4 ounces. Add entire contents to differential.
Modifies excess clutch plate friction.

Did anybody ever tell you you're a pain in the

6ytwady.gif


I actually went out in the garage, in 15 degree weather, moved a half ton of junk to dig out a bottle of friction modifier and scanned it about a dozen times, just so I could read the fine print.

Clutch chatter has never really been an issue for me, but the bias changing sides and trying to throw the Jeep sideways, is rather noticeable in the mud under throttle without the friction modifier.
 
Last edited:
Ecomike said:
Oh, and by the way, I got started on this fluid change, rear end inspection because of the clatter marble noise I was hearing on hard right turns under power at less than 10 mph.
Click to expand...

Have you checked your front hubs yet, I had what I thought was rear end noise, then I was convinced it was in the transfer case, turned out to be the right front hub. The clatter marble noise you describe sounds familiar.
A typical diff check for me, grab the axle with the drum off, try to move it front to rear. In and out doesn't really count for much, except in the non c clip axles. Grab the yoke and check for any bearing play. See if you have any seepage at the seals.
When you have the back cover off, save the oil and look at what comes out, filter it if necessary. Inspect the spider gears for rounded edges, blue or black discoloration or excessive side play or the clutch pack for obvious signs of wear, see what comes out with the oil. Pry up on the carrier, you can feel the amount of carrier bearing wear, it should be almost zero.
If all the bearings are good and the diff is still noisy, it's likely fair wear and tear and will in all likelihood run for years or until the neighbors complain.
Had a buddy recently replace the outer axle bearings, which didn't help any, we finally localized it to a rear tranny bearing. Sound really travels in the drivetrain and can really fool you.

Drive train noise can be really hard to locate.
 
Last edited:
On my 94 I used RL's 75w90 w/ LS additive and still had to use the bottle of friction modifier that came with the Auburn to get the chatter to stop. I haven't heard of anyone putting in "too much" friction modifier so I think it's better to err on the side of excess. I'm swapping that axle onto my 96 sometime in January(bout time for some LSD, discs, and better gears;).
 
Most additives are two ounces per differential change. Also, there will probably be a "per gallon" mix rate on the back of the bottle - divide by four for quarts.

No, it won't hurt anything to add LSD FM to a differential that doesn't have a clutch-based LSD. Think of it as an "anti-wear" additive.
 
8Mud said:
Did anybody ever tell you you're a pain in the

6ytwady.gif
Click to expand...
:laugh2::roflmao:
No, at least not recently, LOL.:D I must admit I laughed my
6ytwady.gif


off when I read this! It made my day! Sorry to be such a pain! But isn't that what friends are for?:D

Oh, and hopefully you have warmed back up a little since your trip to the garage. HAPPY NEW YEAR!
 
Last edited:
w_howey said:
The FSM shows 3 pints, and my AMSOIL book shows 3 pints for the D-44.

But you would still fit it to the bottom of the fill plug.

If 4 pints is what actually what fits. Then you would need 4.16 oz. of LSD additive.
Click to expand...

Well I got 3.5 pints into it and added 5 oz of the TransX brand LSD I had on had. It was not quite level, so its a little over the bottom of the plug, or wioll be when I set it down level again.
 
8Mud said:
Have you checked your front hubs yet, I had what I thought was rear end noise, then I was convinced it was in the transfer case, turned out to be the right front hub. The clatter marble noise you describe sounds familiar.
A typical diff check for me, grab the axle with the drum off, try to move it front to rear. In and out doesn't really count for much, except in the non c clip axles. Grab the yoke and check for any bearing play. See if you have any seepage at the seals.
When you have the back cover off, save the oil and look at what comes out, filter it if necessary. Inspect the spider gears for rounded edges, blue or black discoloration or excessive side play or the clutch pack for obvious signs of wear, see what comes out with the oil. Pry up on the carrier, you can feel the amount of carrier bearing wear, it should be almost zero.
If all the bearings are good and the diff is still noisy, it's likely fair wear and tear and will in all likelihood run for years or until the neighbors complain.
Had a buddy recently replace the outer axle bearings, which didn't help any, we finally localized it to a rear tranny bearing. Sound really travels in the drivetrain and can really fool you.

Drive train noise can be really hard to locate.
Click to expand...

Well I inspected the old oil, and the bottom of the diffy case and the gears, and the play in the entire rear end with the rear end elevated, the tires still mounted, and the Tranny in neutral. I could find no unusual slack or sign of excessively worn gears, or bad teeth, or signs of bad bearings, no seal leaks, no blue or black discoloration, fluid looked pretty clean........ No real signs of significantly sized metal particles in the fluid, just a very small trace of normal metal fines from normal wear and tear.

If it was the rear end making the noise, it must have needed more LSD than it had, which is my best guess as it sounded typical of descriptions I have read of an LSD rear end with out LSD in the oil, or with out enough of it on tight (sharp) powered turns.

That said, I did find a U-joint on the front drive shaft that has some movement, not totally shot yet, but it wont be long, so it might have been the source of the noise too. I amd replacing it in the morning if I don't freeze first. I also found and fixed a missing bolt hanger on the exhaust pipe between the exhaust manifold and the Cat converter.
 
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