HEAD questions and a oil question

[dy5]

ok i checked my compression today.... 125 70 100 120.
so im pretty sure my head is either warped, or i blew a head gasket.
the problem that had the car down was that i overheated her pretty bad. my pocketlogger was ####ed.
so could my head be warped, or is it the gasket, how do i find out?
oh yeah
and does mobil 1 synthetic gear oil work well in dsm trannies?
i heard it eats the synchro's away.

 

[BUCK]

What I interpert my 91 AWD Manual to say is that Petroleum ONLY Hypoid GL 4 or 5 is OK in the Tranny - NO SYNTHETIC in the Tranny due to the Viscous Coupling - Synthetic is cool in the rear end & AWD transfer case.

Sounds like that is the least of your problems - Good Luck.

 

[flytalon93]

I use SynchroShift II in tranny and Amsoil for transfer case and rear end. Very good results.

As far as your warping issue, you already did the compression test so while you are replacing the headgasket you might as well get the head milled. Would really hate to have the motor back together with the new gasket just to find out the head is warped. Then you'd have to start all over again. Your numbers seem low, so it probably wouldn't be a bad idea to initiate a rebuild.
Good Luck,
Steve

 

[dy5]

#### a rebuild, the engine has only 40k miles on it, blah besides i have no damn money, it would take me a year to rebuild this bi***. i just dont have the money, and i need the car up and running.

 

[Defiant]

Originally posted by BUCK
- NO SYNTHETIC in the Tranny due to the Viscous Coupling -

The VCs are sealed units. They don't know what's around them.

 

[dy5]

so synthetic is bad? i take it, i heard it eats away at the copper, in the tranny or something.

 

[BUCK]

Everyone seems to concur that Synthetic is OK in the AWD Transfer Case & Rear End - NOBODY concurs on the use of GL-5 in the Tranny - The manual says GL-4 or 5 Hypoid is Ok but after reading what Defiant posted about the VC's & reviewing the VFAQ - I'm unsure...

From the VFAQ: http://www.vfaq.com/FAQlocator-index.html

Redline MTL/MT90 info
Key passage:
"Most manufacturers of manual transmissions and transaxles recommend an 80W or 90W GL-4 lubricant. GL-5 gears oils which are required in hypoid differentials are not used in most synchromesh transmissions because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Typically, the use of a GL-5 lubricant in a synchromesh transmission will shorten the synchronizer life by one half."

Pennzoil info (may not load in Communicator, loads in IE)
Key passage:
"If an API GL-5 gear oil is used in a application where API GL-4 gear oil is called for, chemical corrosion of "yellow metal" components may occur, such as bronze synchronizers, brass bushings, etc. This may lead to shifting difficulties or shortened equipment life."

GEAR OILS...
DSM transmissions are very sensitive to lubricants, so the oil you use will have a direct effect on how the transmission shifts. Again, synthetics are superior to conventional oils. First, a GL-4 spec oil must be used in the transmission. Do not use a GL-5 spec oil or you will damage the synchros, the GL-5 additives are corrosive to the brass synchros. Three brands have been found to work best, Red Line MTL (or MT90, which fits DSM spec better), BG Synchroshift, and GM Synchromesh (not actually produced by General Motors). All have their followings. Some cars work better with one and some with another. It can be said with certainty that any of the 3 will improve shifting and transmission life dramatically over standard gear oil. This has been found at the factory too. If you suffer notching shifting and some gear grind, especially when cold, these products will help. If your transmission is notchy all the time and several gears grind, you may have to have synchros replaced or the transmission rebuilt. Depending on your car's age you may be eligible for repair at the dealer through some factory TSBs (Technical Service Bulletins) which replace the synchros with updated parts for a nominal deductable.

For AWD cars, GL-4 or GL-5 synthetic will work for the transfer case and rear end. Redline or any of the synthetic gear oils will work fine here. 75W90 seems to be recommended.

(TS: Note: I personally run MT90 in the tranny and transfer case (so 3 quarts just about perfectly fill the tranny and transfer) and Redline 75W85 gear oil for the rear diff. Redline recommends a mix of MTL/MT90 for DSM trannies, I think straight MT90 works better in warmer climates. The colder the climate, the higher percentage of MTL you'll probably want. People in really cold climates seem to have best luck with straight MTL.)