As an aside, the diff in my car was converted to 3.07 D44 ring and pinion years ago. I made spacers to fill the larger holes, although there were seemingly informed forum members who didn’t think it was necessary as the clamping force would be adequate. I used the Daze cars parts list which was accurate. At the time it was less costly to purchase a full D44 kit and supplement with those parts unique to the Salisbury as opposed to buying the specific D44 items individually. There are a number of old threads on this topic…and they include all the same “observations” regarding (inconsequential) inaccuracies in the Daze write up.
The specification for the stock E Type LSD state that the clutch pack will release at 70 ft pounds torque more or less exerted on either hub, with the other locked, so the effect of the stock LSD is not huge. This is how you test your diff to see how good the clutch pack is. The internal pressure in the stock clutch pack is maintained by a single, per side, dished plate which acts as a spring when the differential case is bolted together (it gets flattened out relative to the other plates and clutches). You can, or at least could buy a “heavy duty” clutch pack from Dana for the Jag diff, which has a single dished plate, and a single dished clutch plate per side, so double the pressure. I’ve never been able to find assembly instructions for a heavy duty pack for a 44, but have determined by trial and error that the clutch plate nestles into the dished plate each side. Also I don’t know the “breaking” torque for this but it seems considerable. I autocross so I have these heavy duty packs in both cars.
The Dana 44 must surely be one of, if not the most, popular LSD diff’s made. There must be millions of them out there, but there are a lot of variations of them so, as said, you can’t assume parts interchangeability.
The effect of the clutches only has to be enough to start the ramping/wedge effect of the cruciform pins in the carrier slots. When that begins the clutches are rapidly clamped tight, which is why Thornton who designed it called it Powr-Lok, because it only locks under power. Actually it locks under braking too and you can specify different ramp angles for accelerstion and deceleration.
Too much clutch effect in a street car makes juddering or groaning noises more likely in tight corners like turning into a driveway or parking lot, even with oil additive. That makes customers more likely to complain, unlike a competition driver.
Not really. Eventually the clutches will wead quicker. I think as Doug said there are probably lots of Jags with shagged clutches after 50 years but the XK or V-12 still have enough torque to clamp the clutches tight even if the Belleville plates hardly can.
Both diffs in my cars are quiet, and both have the friction modifier additive. The one in the car with the stroked engine is easily overpowered and I get significant wheel spin on the inside tire at full throttle. This engine’s been on a chassis dyno and appears to have around 360 ft pounds of torque so perhaps that’s not surprising. The prior engine which was also modified, but would have been in the 300 -310 ft pound range did not overpower a similarly built diff.
A more aggressive ramp would probably help the wheel spinner, but the noise or grabbing issue is definitely sporadic. Some do and most do not. I’ve never owned a Jag that did it but have driven someone elses.
I think plate surface microfinish and type of lube are the two dominant factors, but it’s only an opinion based on decades of multiplate oilbath bike clutches. Certainly there are some oils and additives that should not be used due to clutch slip.
Does it hurt to put in more of the recommended additive than is called for? I used gear lube made for limited slips that is suppose to not need the additive but I wondered if it has enough to satisfy Jaguar’s requirements.
John I don’t know the answer to that. I think I put too much in the differential that’s being overpowered, by soaking and assembling the clutch pack with it straight, and then adding a full bottle to the oil, so maybe. Peter might know. I don’t know exactly what the friction modifier is or does, or how it does it, and the internet stuff goes both ways but doesn’t contain anything I think is authoritative.
Hi John,
I had a retailer tell me the same thing with Redline differential oil, that I should add the friction modifier. I chose not too, taking the line of reasoning that the ‘tribologist’ responsible for the formulation of the gear lube probably knew more about it than the trusted salesman. JM2CW, (and probably worth less that that).
Cheers,
LLynn
PS: been doing it that way now for 5-6 years and no issues, noises etc.
I don’t know if the answers are even knowable in practice. It’s like developing new drugs - you can’t test for every possible drug interaction. There are so many oils, synthetic, vegetable or mineral, with differing additives in differing bases and used at differing concentrations and spring pressures etc.
I use Shell LSD-compatible gear oil. Someone told me one additive is canola oil but it sounds unlikely, except it could be for all I know. I actually prefer the inside wheel breaking traction compared to the back snapping out suddenly, but on balance would have an LSD rather than not. My Buick Roadmaster Wagon has one as part of the tow pack
Pete, An LSD transmits power via the path of most resistance and applies bias to outer wheel over run in turns. What does this have to do with the torque applied on the pinion? What you’re describing is spool like behavior which would result in a bit a chirping in turns from a worn out set of clutches? There are 3 other ways to stack the discs in a powr lok resulting varying degrees of aggressiveness. The workshop manual only shows one.
Hi Doug I’d be very interested if you could post the three ways. There is a virtual lack of material on this, or at least I’ve been unable to find it. I’ve seen alternative ways to stack the discs but no explanation as to the effect of it.
One other thing. I don’t really understand LSD’s, planetary gear sets etc, so a lot of the action taking place in the diff is beyond me - but I’m prepared to try to learn. The Jaguar manual differentiates how the diff works in straight ahead mode and in turning mode. It states that in turning a corner diff action is partially reversed and the diff gears become a planetary set. In this state it reports that the differential is now similar to a conventional diff and the wheels are free to rotate at different speeds. Ok I think this applies only when there is no power applied. However one page over it states under the heading “Power Flow in Turns” that while “…normal differential action…” is happening in cornering “At the same time the differential applies the major driving force to the inside rear wheel, improving stability and cornering” . Huh - the inside wheel is the one with the least traction.
always looking to learn…my V12 Daimler VDP, I replaced the auto trans with Supra W57 5 speed manual and XJS clutch…it had a very bad habit.
If cornering in very slippery conditions, when letting out the clutch changing from 1st to 2nd, it would savagely wag the tail…even with no throttle input, just engine torque
when I say “wag the tail”…it was diff action locking & unlocking each axle repeatedly, and you really had to just steer the bucking beast…or try to stab the clutch. I suspect there was also may have been oil or rubber on a newly wet road
It does suggest the Powr-lok is more aggresive, as my Dana-equipped 4wds, I only ever got one or two corrections, even with 4.55 diffs, and backing off the throttle eased it
I do know plates in an LSD can be set up to allow for various level of action, I know a guy that is into drifting, and they are constantly changing diff settings
Thanks Doug. The Dana manual is very helpful – it sets out 3 and 5 friction surface arrangements of the discs and clutches with an explanation of each. Great stuff! I inadvertently got it right in assembling my diffs with the 5 surface arrangement.
excerpt… " A limited slip (LSD) differential is simply a standard differential (also called open) with either a fixed bias or dynamic biasing mechanism which serves to only “partially” lock up" the two axles by way of clutch plates or special gear design. However, most require that both wheels still have some traction on the ground to operate and even when new will cause a wheel in the air to spin uncontrollably so as to be completely ineffective where off road traction is required. "
Its strange that Dana factory LSD in Jeeps, Isuzu and IH Scouts all are like this, (being 4wd off-road vehicles, I knew this from seeing it so often in mine & others 4wd), and that a Jaguar would have a diff design that maintains traction with a wheel in the air
according to this data however, an Auburn LSD will
**High Performance Series for standard equipment on most popular cars and trucks. Superb power transfer with more torque delivered to the high traction wheel, even when the loose wheel traction is zero.
