Three 4wd - diff questions

[curmudge1]

Reading Jim's article on locking diffs, I recall a comment about some part(s) wearing out and after a few thousand (50/80k?) miles, you have an open differential (i.e., no locking).
Q1 - does this apply to the Eaton Gov-lok, too? (factory locking diff) So, after 245K miles, no locking differential effectively on my rear axle?

Read a brief 4wd article in Guns & Ammo, and I got to thinking (dangerous, I know):

Q2 - with our 4wd systems, is the standard front differential a locking diff ? I.e., if I'm in 4wd & one tire in front spins due to lack of traction for whatever reason, mud,ice,snow, etc., does the other front wheel not get any of the front power/torque?

Q3 - with the standard 4wd, when 4wd engaged do both the front & rear axles both get power, or does all the power go to whatever tire spins easiest?

Thanks, just want to know what I've got going for me.

[More Power]

Q1 - does this apply to the Eaton Gov-lok, too? (factory locking diff) So, after 245K miles, no locking differential effectively on my rear axle?

The article about Randy's Ring & Pinion (http://www.thedieselpage.com/reviews/randys.htm) mentions that the carbon fiber discs used in the Eaton will likely last longer than a typical limited slip. In any case, a whole lot depends on how the vehicle is driven. The G80 in our 6.5 Project truck appeared to operate normally till the clutch disc assembly blew up at about 200,000 total miles.


Q2 - with our 4wd systems, is the standard front differential a locking diff ? I.e., if I'm in 4wd & one tire in front spins due to lack of traction for whatever reason, mud,ice,snow, etc., does the other front wheel not get any of the front power/torque?

The standard front diff is "open". This helps make it easier to turn while in 4WD. A locked front diff just wants to go straight.

Q3 - with the standard 4wd, when 4wd engaged do both the front & rear axles both get power, or does all the power go to whatever tire spins easiest?

The part time transfer cases used in these vehicles split the engine torque between the front and rear axles - equally. If you have open diffs at both ends, one rear tire and one front tire would spin when power is applied on a slick road surface.

MP

[DA BIG ONE]

The 14 bolt IFS diff has 2 locker options;
1) ARB air locker
2) Eaton electric locker

[Kennedy]

I run the E-Locker in the front on my 2002, but like MP said, it is NOT for street use. If you try to drive it, it will push really bad when you try to turn.

Years of mud drag racing, and I never spooled the front. Whith the fronts both spinning locked, too much handling is compromised. Now for truck pulling or drag racing on a safe closed circuit, it's OK. Also for getting unstuck and low speed maneuvering in adverse conditions off road it is excellent.

[markrinker]

I changed front and rear diff fluids in #3 yesterday (2003 3500 4.10 dually). At 35,000 the gear oil was coal black and 'had globs of stuff but no metal shavings' in the rear according to the service tech.

Factory spec called for synthetic in the rear, dino in the front. I opted for synthetic in both, since plow trucks spend ALOT of time in 4WD.

Was this a bad decision?

[Turbine Doc]

Originally posted by curmudge1:
Reading Jim's article on locking diffs, I recall a comment about some part(s) wearing out and after a few thousand (50/80k?) miles, you have an open differential (i.e., no locking).
curmudge can you paste link to article you reference I did not find it in my search of forum or reprint books I have.

Jim can you do a repost if you know of article of which he speaks, seems to be a lot of interest in lockers etc of late maybe worthy of a revist to stuff you may have in archives alreayd, I was going to post something I saved from 4 Wheel and Off Road Aug 2001, but if you have a good batch of info already no need to reinvent the wheel.

[nvmtnlion]

I have the RPO G80 also. Is there some kind of maintenance that needs to be performed other than fluid changes?

tbogemirep, with all those goodies, are you also running MIL-L-23699 as your engine oil? smile.gif

[rjschoolcraft]

Originally posted by nvmtnlion:
I have the RPO G80 also. Is there some kind of maintenance that needs to be performed other than fluid changes?

tbogemirep, with all those goodies, are you also running MIL-L-23699 as your engine oil? smile.gif :D :D :D :cool:

[cruzer]

Ronniejoe, Look in feature articles "Randy's Ring & Pinion"

[curmudge1]

Jim's (More Power) first reply has the link to Randy's Ring & Pinion article... I was wondering if the "wearing out to open diff" applied to the G80 option, the Eaton Gov-Lock as well. Seems like it might not, or at least not as much, since in Jim's truck it was working at 200,000 miles, until it destructed.

Seems like I recall advice, maybe in the owner's manual or not, about not driving in 4wd on dry pavement so that the front wheels can slip... if there's an open diff in front, then why not drive on dry pavement in 4wd? Other than fuel efficiencies, etc. Gotta go re-read the owner's manual... someday soon, when I have spare time. ;)

[mklein]

The 4wd on dry pavement presents a problem with the front to rear being locked and binding as a result.

[Turbine Doc]

Thanks CM1 did not know if that was same post or you had found another gem of info on the site, the search engine does a pretty fair job of finding them but not always.

[More Power]

Mark, A service advisory was issued a couple of years ago to all northern dealeships advising them to install a synthetic lube in the front axle assembly of all 2500HD/3500 4x4 equipped trucks. GM found that dino lube was causing (or contributed to) seal leaks in very cold weather.

MP

[markrinker]

Thanks, MP. Sounds like I'm ready for winter duty.

[Turbine Doc]

Originally posted by ronniejoe:
</font><blockquote>quote:</font><hr />
tbogemirep, with all those goodies, are you also running MIL-L-23699 as your engine oil? smile.gif :D :D :D :cool: [/QB]</font>[/QUOTE]Good one NVMT& RJ I missed it on 1st read, for those that don't know that is Mil Spec for jet engine oil.

[nvmtnlion]

Yes, it is. smile.gif 7 years around LM2500's in the Navy. breathing that stuff.

[Turbine Doc]

Cool, Hey Ronnie Joe another turbine head; Not to get off topic too much which ships, I'm factory rep on site Pascagoula doing LM2500 & 2500+ installs, precommed Scott DDG-995 6-YO GSM GLakes 80-81 then out in 86 GE ever since. Profile says network engineer bet you were an E, well I won't hold that against you. :D

[rjschoolcraft]

Yeah, I picked up on that. ;) Not too many non-turbine guys know about MIL-L-23699 or MIL-L-7808 for that matter. :D

[ 12-09-2004, 09:19 AM: Message edited by: ronniejoe ]

[nvmtnlion]

First, (and on topic) about the G80 RPO axle, I am considering changing the fluid as soon as it warms up a bit. If there is something that needs to be done as far as maintenance while I am in there, please advise. I think I am going to go with AMSoil in both diffs while I am at it. Is this a good plan?

Second, (and more off topic) Yeah, I was 6-YO GSE +1 extend. On USS Aries (PHM-5) and then Precom USS Cowpens (CG-63) for the rest of my career. I ran EM02 for 2 years so not "Just an E"

John
mtnlion@gmail.com

[Turbine Doc]

Shame all PHMs (jet powered patrol/hydrofoil/missle boats) are gone they were fun, a bit of a PITA to keep up, 1st thing GE did was send me to engine rooms to do FSEE cal and setups; tech manual in hand I learned/reinforced tron stuff the hard way, can navigate Woodward & GE Salem digital controls now as well so I'm not just another M.

USN should have cross trained from day one the M vs E thing not effective way to do things; bottom line engine ain't working regardless of a electrical or mechanical cause.

[norm]

I keep wondering if all G80 (RPO="locking rear differential") axles have the same components and operation. My understanding is that gov-locks do not have clutch packs, and therefore no limited slip operation, only locking as described in some other threads. This has been verified in my current '95, and in a '98 that I bought new.
So you should not be worried about clutch wear in these units. Perhaps the locking mech. wears out?
It also seems like G80 might not always mean gov-lock, depending on year/model/etc.
Do the newest gov-locks have the governor locking mechanism plus clutch packs for both locking and limited slip operation?

[DmaxMaverick]

Norm

Your suppositions are correct. 1995+ have Eaton Gov-Loc lockers. GM got away from L/S units and has not gone back, for trucks, anyway. Some H/P vehicles still have a L/S option, like 'Vette, T/A, and Z28's.

Early Gov-Loc units had only a locker, with no friction surface. Current models (not certain when the change was incorporated) do have friction material in the setup. They have a carbon clutch as part of the engagement hardware. The clutch acts like a synchro, softening the engagement of the locker, and is only under friction conditions when a lock-up is called for. This has made the unit more civil on the road, yet allows the unit to remain aggresive in off-road conditions. Eaton has anticipated the clutch in current models extends the life of the unit, as it "cushions" the impact on hard parts. They state that the wear of the carbon friction material will outlast the hard parts (R/P, bearings, gears, seals), and has no negative effect on same. Eaton states the friction material that does wear will show up in the lube and darken it, but has no adverse effects on it's lubricity or other properties.

Contrary to many opinions in this (and other) threads, some limited slip units are suited for off-road use. My '85 has an Auburn L/S in a 1978 12 bolt (got tired of rebuilding that POS 10 bolt), and will lock absolutely positive, like a locker. Auburn's recommendations must be followed to get that performance. As much as I hate it, I must use Dino lube in it. Synthetic lube, or the wrong lube, will reduce the performance considerably. I use GM rear axle lube (I forget the #) and 2 bottles of GM additive, as recommended by the Auburn rep. The things I hate about it is the lube is expensive, and only comes in 13 oz. bottles. I have tried other lubes/additives in the past and they just don't work. If I use an "off the shelf" lube and/or additive, the rear end will act like many here are complaining about.

Many of the products available will work as advertised and last a long time. Problem is, most will fail and get a bad rap because users don't install/maintain them properly. This is especially true when many of the users rely on "quicky lube" to service them, and many dealers fall into that category.

[curmudge1]

Norm, or anyone else, what about the 1994s (and earlier)?

My 1994 Blazer 6.5 TD has a "locking differential - Rear Axle", RPO Code G80, so what is it? And, would synthetic axle lube be bad for it? Or good?

Thanks.

[norm]

I don't really know from the year, but would inspect it to figure out what was there.
I would start by jacking up the rear of the truck and try to rotate tires with trans in park and then in neutral. (brake off) If the tires rotate in opp. directions quite easily, then it's probably a gov-lock or a completely worn-out-useless limited slip.(or open of course, no G80) If it takes some good effort to turn them that way, it might be a worn l.s.. If you can't move them at all, it is likely a functioning l.s.. When in neutral, if the tires move the same way, prob. l.s.
The only sure way is to open it up and take a look. You can usually spot l.s. clutch packs at the sides of the carrier. The gov-lock mechanism has some fly-weights and other parts around the outside of the spider gear area - they are pretty unique and easy to spot.
I'm no gear expert, just speaking from what I've owned and seen...

[rjschoolcraft]

I had a "gov-loc" G80 unit in a 1986 S-10 Blazer from the factory. Since the spider gears were shimmed incorrectly, I had the "opportunity" to rebuild with a new set.

The gov-loc had the flyweight and latch mechanism that actuated a cam which loaded clutch plates behind each side gear. This requires a difference in speed between one wheel and the other (some of the manuals say 100 rpm difference) for the mechanism to engage and drive both wheels. I've looked at GM service manuals for several years between then and now and believe that all of this type work the same way.

[norm]

Thanks RJ - info I have seen indicates no friction modifier needed for gov-lock (at least for the years I have owned). Is this what you have found?
How about curmudge1's question on synthetic?