Topic: Synthetic gear oil?

[Speed]

Hi all;
   Hey,all the boxes (trans.,T/C,both axles) leak pretty bad right now on my '81 Toyota 4WD pick up; what I'd like to know is if I re-seal them,one unit at a time,will they work okay with synthetic 90W in 'em? First will be the transmission,a G50. (The reason I ask is that on my Bronco II I'm told by someone who tried it that changing to synthetic gear oil renders the syncronizers useless.  Don't wanna have that happen on this truck.)
Speed

[Goldrush]

Use it in everything. Won't hurt a bit.


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[Nation]

Yeah synthetic is fine to use after break In. If used during break in the sync rod may/will not break in properly or at all. Also, synthetic will find any small Crack to leak from...

[Speed [OP]]

I learned the "finds leaks" deal when I replaced the 283 in my '62 Chevy one ton with a 355 I got as payment for some trailer moving. Drove it for damned near a year and it didn't use a drop of oil,so I switched it to synthetic. Ran it all Summer without a problem,drove it to Reno to deliver a pick up on a trailer,and it ran out of oil in less than 150 miles. Filled it back up (4 quarts at $9.00/qt.),got to Reno and it was out again. $86.00 for gas,$72.00 for oil! Changed back to Castrol 20W50,used less than a quart to get home.(Turned out the Synthetic "found" a broken piston ring for me. Thanks.  )
   I've been using 10W Mobil 1 in my B-II's transfer case in place of ATF for as long as I've had it,and in addition to getting a couple more miles per gallon than before,it seems to work great.
   BTW-I rarely have a reason to worry about "break-in procedures,as the only new vehicles I've ever owned were my first two Harleys. Everything else is more towards the "keep it alive for one more year" end of the scale.
   Speed

[blackdiamond]

The syncros do require a certain amount of friction to work properly. It seems that Redline is supposed to be ok.

[jssgbsn]

Are they leaking because of the current seals?

If so, then replacing the seals would solve everything. 

I use synth for everything, on every vehilce, all years, and havent run into any leaking issues from using it, versus, petro lube.  I can't imagine you would experience leaks from synth if seals were replaced.  Leaks happen from old/bad seals.  Synth can 'reveal' leaks from bad systems, but the leak has nothing to do with synth v. petrol. 

My 22re consumes a lot of oil, more from synth v. petrol, but I don't mind using synth even though it is gauranteed to get burned up quicker.  I just want the engine to last as long as possible before I need to rebuild it, and in my opinion synth will do that better than petrol.  I could be wrong, but I'm okay with learning that lesson, if I have to, on the off chance.

I see lube as there to limit friction and heat.  Synth is better for doing that.  So that's what I use.

(I use Royal Purple, and I been using it before most people even knew about them)

[MRHilux87]

I always run synthetic these days. Not expensive in the big picture of engine costs and I've never experienced it "finding a leak.".

[Speed [OP]]

"Synth can 'reveal' leaks from bad systems, but the leak has nothing to do with synth v. petrol." 

My experience has been that,if your engine has good seals already and doesn't have loose main bearings,the synthetic will probably work fine;if a seal is "marginal" it may seal fine with regular oil but leak with synthetic. I also know that an axle ot transmission with loose bearings may seal okay with standard gear oil,but leak with synthetic gear oil. I have a '54 GMC 2 ton with a 5 speed main/3 speed aux./2spd axle.  I'd love to run synthetic gear oil in all the boxes,but each unit has worn bearings that work okay with 90 wt. but would need rebuilding and seals upgraded from the old leather seals to expect the synthetic to stay inside. (LOTS of $$$ to save a few mpg,and the longevity difference wouldn't be a concern. Even as it is the truck will likely outlast me.) On closer inspection,it looks to me like the drivetrain leaks are down the "Critical Issue" list quite a ways.
    :screwy:HERE'S where this should probably be shuffled to the "Engine" forum....
   Regarding the Toyota,it now appears the engine is the worst offender for leakage. I gave it my absolute best shot at sealing the timing cover-(NEW oil pan gasket and timing cover set,Permatex #3 on both sides of the gaskets,replacing the "Heinz 57" bolt assortment with OEM bolts to be sure everything gets the right torque and number of threads engaged,and a can of STP Engine Oil Stop Leak. No Joy. It appears,from what I can see,that it leaks from the head gasket where the timing cover fits against it (This is the one leak I was MOST sure I'd be stopping. ,and the timing cover bolt that the alternator adjuster is on. THIS leak concerns me because it APPEARS there's about an 1/16 inch gap there,between the back of the cover and the front of the block. I'm pretty sure THAT is leaking a lot,but I haven't figured our how to seal everything up;the head gasket leak will likely require a NEW head gasket,and in my mind,that means a rebuild,which I'm not able to do until Spring. Can't tell you how tempted I am to look for a good running junkyard replacement slightly later 22R or 22RE longblock,swap my intake over,and find a header to replace my exhaust manifold,which is in bad shape. (rusted up bolts,cracked at one port,etc. ) Might be worthwhile to see if I can get the engine that came from the parts truck I'm negotiating for.
   Drove the truck over the Summit to Spring Creek last night and some guy flagged me down at the traffic light to tell me my truck was on fire. I almost laughed-the smoke was just the oil spraying onto the manifold. Looked worse than it was. THIS time it only used half a quart of oil in 20 miles!
   Speed