Differential Fluid

When to Change the DIfferential fluid? and what type to use when I do?

I have a related question....I haven't seen too many posts on people "upgrading" to say a high quality synth from Royal Purple or Redline in place of the OEM Isuzu fluids...is everyone simply going to the dealer? Quite frankly I'd like to go to my local performance shop and fill up with Royal Purple products. Especially after my local dealer changed their "service" intervals three times in one year, none of which match the service intervals in the driver's manual. To boot, cost jumped from high threes to $500 big ones.

I do know that the rear differential would require a friction modifyer (available from Isuzu and I'm sure from RP or Redline).

Any thoughts? Anyone doing fluid changes in the driveline themselves?

100% Mobil-1. Here's where I use it: Engine, oil filter, tranny, differentials, transfer case and all greasables. Best stuff ever! And it already has the additive in the gear lube for the limited slip. All you gotta do is drain the old stuff and pour in the new. Check AutoZone if you have one as they have about all the products.

Royal Purple has a new and unique diff fluid that is 75-140w so it can be used in a wider temperature range than any other fluid I have seen. Most all synthetics do NOT require you to use the LSD additive although I have heard from those using Mobil 1 that have had to add it to stop the chatter (and excessive wear on the clutches).

Be sure to use teflon thread sealer at least on the front bolt you remove to drain or it will wick down the threads and drip. I use it on all plugs I remove that hold in fluid.

I just changed to Royal Purple this past weekend....

Front dif uses the bottom most retaining bolt as a drain...

Do yourself a favor...get a drill pump from a hardware store...it makes fluid removal and replacement much easier.

Ojmagg, did you use the additive with Royal Purple? I am going to try this on Saturday or Sunday, and want to make sure I have everything before I pop the drain. And you are talking about MaxGear, right?

How bout the transmission? Is fluid/filter change required? Royal Purple does make something called Max ATF which is Dextron III compatible. I should probably just crawl under there and explore I guess.

Thanks for the teflon sealant tip...I wouldn't have thought to do that.

I've heard similar concerning Mobil 1 and the differential. I didn't use any friction modifier with the RX7's differential (Torsen) and Royal Purple. Most that use the KAAZ (clutch pack) must add a bit of modifier or drive in figure 8's for hours to break it in and reduce the noise.

What's the nicest thing about changing fluids on a VX? No jacks!:D

Royal Purple Max Gear Oil already has the LSD additave...I can feel a slight difference in the performance of the truck. I'm getting better gas milage and there is less noise form the drive train.

Hey I_Wanna_Retire,

If you do this this weekend, could you let me know how it goes and what you run into. I've been thinking of doing the same thing but have no experience with anything other than changing the oil.

Thanks.

I'll let you know when I do it, but it doesn't look like it will be this weekend as I could not find anybody in the triangle that carries Royal Purple.

Does anybody know the socket size for the plugs in the rear differential? Me no have complete set so I have to buy or borrow just the ones I need.

Thanks

I believe it is a 25mm

Ok, I did it, changed the front and rear differential fluid, and it was fairly easy even for an electrical engineer :)

I had to order Royal Purple over the internet, as I could not find around here. I also had to buy a 24mm socket wrench to remove the rear drain and fill plugs, and the front fill plug. The front drain plug is a 12mm. All wrenches could be regular box wrenches except for the rear drain which is recessed.

I did not go for the fluid pump, but just bought a 60 cent hunk of plastic tubing, part of which I duct taped to the gear lube nozzle, acting like an extension so I could reach the filler holes without making a mess. The other part I used as a siphon so I could remove the fluid that does not drain by gravity. Did front and rear in about an hour.

Grrr, I am pumped now, what's next, ahh, me thinks synthetic tranny fluid....

I'm going to do my 30K this Friday and after reading this thread I be buying the Royal Purple syn rather than Dextron 3. Now, does the syn postpone the next fluid change beyond 30K? Anyone?

Scott

Castrol in engine, tranny, transfer case, & diffs

on tranny to fill use Valvoline pump part # VV816 to make life more simple

on diffs...24mm front/rear & do not overtighten the bolts...they do not need much force

I was just quoted $971 for transmission flush/fill, front and rear diffs change, turned rotors and new brake pads, and a brake system 'flush'... yeah right
Anyway, they are still doing the transmission flush, then I am going to do the rest, my question is this, are there any writeups for the diffs, or is that simple... and is the transfer case easy to drain and fill? Let me know, I'm doing all this in prep for an Ohio to Florida drive at the end of the month. I bought the wheelbearing seals, the brake pads and all that, I just need to take off the pads rotors and take the rotors somewhere to be turned, then I can finish the job the next day... Thanks

Diffs are easy... you just unscrew the drain bolt, drain, screw it back on, and fill!

$971 is COMPLETE and UTTER NONSENSE!!!

front diff drain bolt is the lowest most bolt......

I think if I remember correctly that Isuzu charges like $40 a diff to change your fluid...
whoever charged you that is bucking for early retirement!!!

for that price I could do that for $200 and the other $771 would be put in my Super Charger Trust fund

What's funny is all I asked was "Drain and fill transmission (coupon for flush and fill) also change the tranny filter, drain and fill the diffs, and btw, there's a brake warning light on, see if it's the emergency brake (fluid levels look fine)"
That was at 8 this morning, by 11 it was $971 for above...

WOW! Just had ALL my fluids changes two days ago. Based upon Many post I saw here I decided to go with Mobil 1 (AFT, Gear Lube, Additive, the whole works.) Did a full tranny flush...you name it. (Boy, I wish I was a mechanic) I went to a lube shop that specialized in Mobil 1 here in San Diego and after several hours the final damage was $455 big bucks. But the VX runs much smooooother. Thanks to EVERYBODY who had something to say about the matter. Every commit helps. Well that's my 2 cents!;eekr;

I had the diffs and trans serviced at the local Isuzu/Ford dealer. They use the GM LSD product in the front diff. I put in Royal Purple in the trans and xfr case.
Roy

The lsd fluid in front is a waste of money since the front diff is open.

The front diff is not limited slip?
What does OPEN mean?
Roy

Opps, I forgot. The 455.00 also included, replacement of the serpentine belt.

I just got a quote from the dealer of $459.00 for the 30,000 mile service including repacking the bearings.

The front diff is NOT limited slip.

I am gonna switch to Coastal Full Synthetic 75/140 $12 a quart


I saw some Mobile one at the Auto store Shucks (Kragen) for $16 a quart.....what do you get for $16 a quart...for $16 a quart it had bettr do more than just lube my truck it had better lube me too!!!!;eekp;

Got my Mobil-1 gear-lube at AutoZone for a little over $6 a quart. There's a set of photos in my gallery showing where all the fill and drain locations are for the diffs. Got the LSD additive for the rear diff at AutoZone too for about $7.