Changing & checking the trans-diff oil...

takza · Post by **takza** » Fri Aug 06, 2004 8:29 pm

I changed my trans & diff oil after 28 K miles. Some like to do this every 15 K miles...the manuals I have say it isn't really necessary at all unless you need to change the viscosity of the oil.

My basic opinion is that it should be changed at at least the typical number of miles for a manual trans/diff oil change...(30 K miles)...especially since most of these cars have pretty high miles on them.

I also want to use an upgraded oil to decrease wear, protect the trans/diff components, and possibly improve MPG & power. The rear diff isn't really in use most of the time, but when you do need to use it...you definitely need the most power and least friction you can manage....so I use the same oils in it.

Last change I went with around 50% 75W90 synth and 50% 75W90 regular gear oil with some added moly additive. This time I went with 40% 75W90 synth and 40% 85W140 regular gear oil with 20% Hyperlube Racing Formula additive.

I HAVE been going with lighter weight oils, thinking that lighter oils would increase MPG...but after reading this article....

<a href='http://www.lubedev.com/articles/mileage.htm' target='_blank'>http://www.lubedev.com/articles/mileage.htm</a>

"Gear Differentials: I always use an 85W-140 gear lube. For gear lubes, I follow the "Snow Rule" which states, "If it never snows where you live, use the 85W-140. If there is significant snow in your area, use the 80W-90. If in doubt, mix the two weights." There is no slipperier lubricant in the world than a nice thick gear lube."

.....but since this guy is into improving MPG and still uses the heavier stuff...it might be OK. Plus it is obvious to me that a heavier oil will cushion the gears and bearings.

Method:

The manual says to have the car level and to check the oil level in the trans at the rear fill plug (there are 3 fill plugs and 3 drain plugs) with the rear drain plug backed out around 7-8 turns. This allows the rear extension housing oil to level out with the rest of the oil in the trans and diff areas...as I was draining the oil I opened and closed this...seeing this effect. There is some movement between the areas...it's just faster with this plug out some.

Problem for me with having the car level is that I can't really get under the car to do the job...so I put the front on ramps....that are 7 1/2" high.

I go out and drive the car till it's hot, drive up on the ramps...and open the plugs into a drain pan.

This time I measured the amount of oil drained...and it came out to almost 5 quarts...almost 1 quart overfilled. I have been checking the oil level at the front fill plug while on the ramps and have been getting some confusing readings.

* after sitting on the ramps for 2 hours cold and with the rear drain plug NOT loosened...the level was just at the front fill plug and ran out very slightly...

* after driving around 1500 miles and checking the oil in the same way (cold) after sitting only 5 minutes...the oil ran out pretty fast....

* after draining and refilling the trans SLOWLY with 4.1 quarts of new oil...with the rear drain plug open some...the oil was just at the lower edge of the front fill plug...while it should have been a fair amount below the hole.

So I'm really not so sure of this oil level checking method. I'd rather have the trans overfilled by 1 quart than low by 1 quart...but overfilling can cause air bubbles to be trapped in the oil (foaming)...reducing it's ability to lubricate.

** Best method with the front ramps might be to check it with the oil HOT and the rear drain plug out 7-8 turns?

Here is a picture of the 3 drain plugs out of the trans....2 of these plugs have magnets in them to trap steel particles...I was hoping not to see any at all, but there are some filings for sure...but not nearly as much as the last oil change.

The center plug (trans) has the most, the front plug (diff) less, and the rear doesn't have a magnet.

Cleaned ALL the steel particles off these plugs before putting them back in.

I also wrapped some sewing thread around the 4WD actuating arm shaft about 8 times where it comes out of the trans to try and slow the oil leak there...pretty obvious I won't be getting the seal put in there anytime soon.

The rear differential is pretty straightforward and can be changed with the car on the ground. Had almost no metal particles on this drain plug.

This job takes longer than it should...fortunately it's only every 30 K miles...but I wouldn't be able to put special oils in the trans while on a rack.

So I SHOULD be set for another 30 K miles.........except for checking the oil level now and then.......... <_<

sacwac · Post by **sacwac** » Fri Aug 06, 2004 8:42 pm

Also, you might want to get a small set of emergency jack stands. Four of them. I have small ones that are rated at 2500lbs each. Well worth it, it lets you raise the car completely off the ground.

Since you have ramps, I guess you could just get 2 for the rear.

I'm glad you didn't have a differential tooth come out of the plugs!!

Did you have any trouble getting the bolts off? These tend to be very tight, I've stripped one before. oops.

Also to anyone draining the diff oils, MAKE SURE YOU CAN REMOVE THE FILLER BOLT FIRST!!! I once removed the drain bolt, then stripped the filler. BAD. DOH.

takza · Post by **takza** » Sat Aug 07, 2004 5:38 am

Since I know the height of the ramps at the front...I'm going to consider just putting a trolley jack under the rear diff and raise it 7 1/2" to get the car level (with extra jack stand supports). A pain for sure. Current method with the front ramps alone isn't very reliable.

I think the metal is from the 2 gear chips on the 3rd gear that have still been wearing back in...vibration is minimal now. Trans shifts very well and makes no other noise than this minor vibration in 3rd at times...except for some throwout bearing noise (?) under certain conditions.

I snug those bolts up pretty well...watch as to what wrench I use with them...I use only sockets and or box end wrenches.

Thereminator · Post by **Thereminator** » Sat Aug 07, 2004 11:00 am

Takza,if the Trans/Diff have a fixed capacity,why cant you just add that amount after compleatly draining it? :unsure: :blink: :unsure:

takza · Post by **takza** » Sat Aug 07, 2004 11:45 am

Thereminator wrote: Takza,if the Trans/Diff have a fixed capacity,why cant you just add that amount after compleatly draining it? :unsure: :blink: :unsure:

That's what I did........but the problem is how to check the level over the next 30 K miles...since I have the 4WD shaft leak?

Easiest might be to just carry a quart of gear oil and find a station with a lift...making sure you do it the right way.

Been checking mine every 3 months...but 6 months probably is OK.

Thereminator · Post by **Thereminator** » Sat Aug 07, 2004 12:47 pm

Do you have a neibor with a steep driveway that would off~set the out~of~level caused by the ramps?

takza · Post by **takza** » Sun Aug 08, 2004 6:33 am

Good idea Thereminator! I'll get out my angle finder and look around for a driveway with the right slope. Now why didn't EYE think of that? :blink:

Maybe 3ACPower could design a device that would cause a localized anomaly in the earth's gravitational field...thus enabling the oil to be checked right.

Or maybe go to one of those MYSTERY places where everything is out of kilter and leans one way?

Possibly, the trans could be tilted in the car so that it would read right when on the ramps?

Or, I could drill a hole in it and install a dipstick...I feel good about the DIPSTICK idea! :rolleyes:

Thereminator · Post by **Thereminator** » Sun Aug 08, 2004 11:30 am

Forget the dip-stick,just use an electronic fluid-level-sending-unit,I think I got one right here... :unsure: As far as useing A~C's super~intelect,thats fine,just dont let him neer Nick as one of them may be an Evil~Genius

.....and that could leed too... :unsure:

!!!!!

takza · Post by **takza** » Thu Sep 02, 2004 6:05 am

My impression of the new gear oil mix?

I can't really see much difference in shifting...but then winter hasn't happened yet.

I can tell that the gears are cushioned more...and they are a little quieter.

The Hyperlube racing stuff is like Lucas oil stabilizer...very thick and if you put some between your fingers it will "string" as you pull your finger tips apart.

After wrapping some sewing thread around the shaft (9-10 turns?) and putting in the heavier oils, the drip from the 4WD shaft is much less...none on the ball joint...just a little on the trans under the shaft.

JIMCAT · Post by **JIMCAT** » Sat Sep 11, 2004 5:43 pm

I need some clarification. My Chilton's manual (#68700) says the transaxle holds 4.1 PINTS at page 1-48. I just drained it and took out about 3 quarts/6 pints. I have replaced 3 quarts and can not feel the oil through either fill plug. Does my '86 manual tranmission 4wd hold 4.1 quarts? If so, Chilton's Manual's got a SERIOUS typo.

thanks for the help.
Jimcat

Thereminator · Post by **Thereminator** » Sat Sep 11, 2004 10:20 pm

Thats a typo,Jimcat(unless you have the special "shruk~down" raceing tranny!).

takza · Post by **takza** » Sun Sep 12, 2004 6:24 am

I have the same Chiltons....and that's what it says. While my Bentley manual says quarts...I put in 4.1 quarts.

If you have it on a rack...then you can supposedly check the level thru the rear fill opening with that last drain plug OUT about 7-8 turns.

JIMCAT · Post by **JIMCAT** » Sun Sep 12, 2004 7:59 am

Bummer, doods. Now I gotta get nasty again. Thanks for clarificaton. Whaddaya expect from a $24 manual? Reliable, accurate, precise information? FFffffppppptttttooooeeee! <_<

takza · Post by **takza** » Mon Sep 13, 2004 1:34 pm

JIMCAT wrote: Bummer, doods. Now I gotta get nasty again. Thanks for clarificaton. Whaddaya expect from a $24 manual? Reliable, accurate, precise information? FFffffppppptttttooooeeee! <_<

Download the '85 FSM available from the front page...I finally did...now THAT'S a manual....somebody did a good job getting it into Adobe form.

I'm finding answers to many questions...like what IS the meaning of life......

I used Leechget...a downloader that allows you to stop and then resume downloads...so if you have a poor connx...you can eventually get it....took me 4 hours.

takza · Post by **takza** » Thu Sep 30, 2004 11:17 am

An article on gear oils:

<a href='http://www.torcousa.com/sports_imports/articles.asp' target='_blank'>http://www.torcousa.com/sports_imports/articles.asp</a>

So what's the best to use? Just guessing...maybe 1/2 synth...1/2 dino gear oils somewhere between 75W90 and 85W140? Best to not use the Lucas/Hyperlube additives due to air entrainment problems in a high speed trans?

Change at least every 30K miles and keep water out!

Might be cool to overfill by a pint or so?

ANSWER: depends on who's talking and what they have to sell? :rolleyes:
---------------------------------------------------------------------------------------

"You can easily test the idea that added viscosity improves lubrication by adding an 85W-140 gear oil to your manual transmission. It will probably shift dramatically easier. In fact too thick of an oil (straight 140) in your manual gearbox may cause so little synchronizer friction that the gears will clash or grind when shifting. This is called cold-clash, caused by excessive viscosity. Conversely, too light a viscosity causes hard shifting and rapid transmission wear. 

In manual boxes that take ATF instead of gear lube, you might use Texaco synthetic ATF. Gear lubes are in a special class by themselves. NEVER add any gear lube to ATF or into any engine for any reason. Synthetic oils are NOT made directly from petroleum, so they are generally safe to add to an automatic transmission.

Manual Shift Transmissions: Drain your existing gearbox and see what is in there. It will be one of these: ATF, engine oil or gear lube. Look at your owners manual to verify. For ATF, use synthetic ATF. For engine oil, order the same or slightly thicker oil.

For gear lube, use 85W-140, but mixed half and half with synthetic and petro based oils.

Gear Differentials: I always use an 85W-140 gear lube. For gear lubes, I follow the "Snow Rule" which states, "If it never snows where you live, use the 85W-140. If there is significant snow in your area, use the 80W-90. If in doubt, mix the two weights." There is no slipperier lubricant in the world than a nice thick gear lube.

Remember you can safely mix most modern petroleum based oils. Just never mix different synthetics or you might create a kind of Frankenstein oil.

In general, synthetic oils carry greater additive content but petroleum oils will adhere better to metal. 

A quick study of the Lubrication Parameter reveals that so called oil viscosity drag at a high temperature is largely another myth. A typical oil at 0 degrees F is about 100 times more viscous that the same oil at 210 degrees F. It seems the best way to get all the advantages of a good lubricant without the disadvantages of a petroleum based oil is to go synthetic--or half synthetic.

The numbers on a can of multigrade oil are confusing to many persons. Just remember the number on the left is the weight (class of oil) at zero degrees F. The number on the right is the weight at 210 degrees F. For instance a 5W-50 oil starts out cold as a 5W but becomes a 50W ONLY after the oil temperature warms up and gets to 210."