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Opel Newbie, Truck Oldie
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Discussion Starter · #1 ·
Just a quick question...how involved is changing the transmission fluid on a 4-speed? It appears it should be just a matter of dropping the pan, dumping the gear oil, using some RTV-type stuff (like the tube of "The Right Stuff" I have from NAPA from previously mentioned in-way-too-deep truck project) to make a new gasket, bolting the pan back on, and filling it up, right?

I would assume it uses just regular 80w90 gear oil? About how much does it use?

The main reason is I want to drop the pan and see if anything is floating in there aside from oil...before buying another tranny...
 

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Super Moderator
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9,765 Posts
After you replace the pan, you unscrew the plug on the driver's side of the trans, it's about 1/2 way up and in the middle on the driver's side. Get a gallon of 90w gear oil with a pump, PEP Boys sells these real cheap, then stick the end of the hose into the openign where the plug came out, and pump away till the gear oil starts running out, stop pumping, and put the plug back in and wipe up any mess, you're done!
 

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Super Moderator
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5,996 Posts
Checking the Transmission for Damage

Remove the ten slot headed bolts that hold the pan in place. When you drop the pan to drain the oil, watch for a spring and ball bearing (the reverse detent ball and spring) that is held up inside the side casting of the transmission. It is above the little round outward "jog" in the pan, on the passenger side. Don't lose them, or you will have created a new problem. And when you reinstall the pan, I like to coat the ball (which goes in first) and spring in grease to help hold them in place.

Check to see how much hypoid oil drains out (unless you have first checked the level through the side hole, and it was full). A full tranny will have 2 1/2 pints, which is bit more than a quart. If it was down a lot, that can cause a noisy trasmission, as well as serious internal damage.

Then, when you have the pan off, take a spray bottle filled with varsol and spray up inside the tranny, which will help clean off the residual hypoid oil and allow you to see better inside. Put it in neutral and have someone step on the clutch, so you can spin the gear sets while flushing it with the varsol (set an oil change pan below it to catch the drips, and watch your eyes!).

Look for obvious metal shrapnel in the pan (where it should be held in place by the magnet that is there). Also look up inside to see if there is obvious gear damage, specifically of the counter gear set (which is the single piece gear set with four different gears), and of the matching gears on the main shaft. Also look up inside the front of the main shaft, and see if you can see any sign of the front main bearing. On Katheryn McCoy's transmission, which makes a sound much like Kate has described (hmmm, coincidence? Maybe not!), the front bearing had eaten it's "shield", and the remaining parts could be seen floating around in front of the drive gear.

Also look for signs of small pieces of what may have once been needle bearings. It is very possible that the "rattle" is actually a "grinding", caused by the needle bearings in the counter gear or the main shaft. You might also drop the drive shaft while you are there to ensure that the PO (Previous Owner) didn't forget to install the thrust spring, which can cause the driveshaft to rattle.

When you go to put it all back together, remember to clean the old gasket off well (unless it comes off clean), and also to flatten the dimples in the pan where the bolt holes are. Otherwise it will leak (even with a new gasket, or even volumes of RTV sealer) between the bolts. And make sure that the four bolts that attach the tranny to the bell housing are tight; if they are loose, that can cause a rattle, and worse will cause the tranny oil to leak out.

If you decide to get more serious, such as actually dropping the tranny to either more completely inspect it or even rebuild it, make sure you have a factory service manual, and not just some aftermarket version. This is a very easy transmission to rebuild, although the parts can get expensive if there is too much to do. And even if you get a good used trany, you might be advised to replace at least the worn synchro rings (typically second and third) to get the best possible transmission for Kate's "original" Opel.

HTH, and good luck!
 

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self admitted opel addict
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227 Posts
on the plug where you fill the tranny ( located next to the shifter under the boot).....whats the trick to keeping that cap on the top of the plug? My plug has a cap on it and it is in two pieces. Is it suppose to be or did I twist it off during removal?
 

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Premium Member
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1,802 Posts
That's not the fill cap, that's the vent, and it's not supposed to come off. If yours came off, then it's broken.

The fill plug is about half-way up on the side of the transmission. You fill with a "slurp" gun or similar pressure fed oiler until it starts to run out the hole.
 

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self admitted opel addict
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227 Posts
the cap was attached to a bolt. The bolt is hollow and has a screen in it. The bolt just screws right out. This is not the fill hole?
 

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self admitted opel addict
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227 Posts
hmmm...what happens if SOMEONE got really stupid and say put the 80-90w in this vent hole?????????:banghead:
Does the vent hole lead to the tranny so that it would drain down and cause no harm???? AND do you HAVE to have the cap on the vent bolt? If so can I soulder it to stay on? Help stupid out here.:D
 

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Mid-West Opeler
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2,411 Posts
picture - 1000 words

the cap was attached to a bolt. The bolt is hollow and has a screen in it. The bolt just screws right out. This is not the fill hole?
hope this helps.... This one is also up for sale.
 

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Premium Member
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1,802 Posts
It would drain to the right place, but how would you know how much is in there? On these transmissions you fill until oil comes out the fill hole, if you didn't even use the fill hole it would be impossible to get the right amount in there.

It's a vent, you can't plug it or it won't vent anymore. Your best bet would be to replace the whole thing, but in the mean time you could get away with putting a small piece of hose over the bolt and bending it so the open end points down to keep things from falling in there.
 

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1000 Post Club
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hope this helps.... This one is also up for sale.
Some transmissions use a hex key(allen wrench) instead of the 6 sided plug on this transmission.
 

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self admitted opel addict
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227 Posts
I put almost a QUART 80-90 in the vent. :eek: filled 'er right up till it ran out! All the time thinkin, hmm, this aint so bad after all! Finally an easy job on the 'ol Opel! SH*@!!!!!

So if I remove the fill plug it will just drain out from the vent on down if it is over full? and if I can't touch any fluid with my pinkie then I'll just add. AM I UNDERSTANDING RIGHT THAT ALL THAT I PUT IN THROUGH THE VENT WILL BE DRAINING ON DOWN TO WHERE IT NEEDS TO BE and it will not cause any harm?
Thanks for the tip with the hose. I'll order a vent bolt from OGTS.
 

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1000 Post Club
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Put a pan under the fill plug. Open it up and let it drain until no more comes out. Make sure the car is level too. After it is done draining, put you pinkie in the fill hole. It should be right at the bottom of the fill hole. If it is lower, you need to add some.

Don't run your transmission until you are at the proper level.
 

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self admitted opel addict
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227 Posts
ok thanks. was really just concerned that all the fluid would be trapped into the vent area somehow. If you guys are saying it will drain on down I am a happy camper again.

Picture did help.

THANKS EVERYONE!!!
 

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'72 Opel GT (Sara)
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2,119 Posts
Too much gear oil?

Is it possible to overfill the transmission with oil and have that affect shifting? I just replaced the O-ring and cup seal on my speedometer drive which eliminated a slow drip there and in the process decided it would be prudent to top off the fluid level. I followed the method described of pumping 90W gear oil in there (Coastal brand) until it came pouring out and then quickly replaced the plug (so I assume the tranny is full to the gills in oil). The reason I ask about overfilling is that now shifting into first gear is tough at first. It requires a good bit of force and a double "click" can be felt as it goes into gear. Eventually, with driving, the resistance lessens until finally it becomes rather easy. Note that none of the other gears exhibit this behavior whether up-shifting or down-shifting. I assume shifting into first gets easier as the fluid warms up (and it is getting colder out even here in Atlanta). So, I am wondering if I should drain some that gear oil back out?

Thanks,

Matt
 

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Not So Newb Anymore
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342 Posts
newman try a different brand or weight. I run 80/90 in all my manual trans cars with the exception of my Subaru due to having a rather expensive center diff inside. I always use Castrol brand in daily drivers. HTH
 

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Opeler
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113 Posts
It will shift better with a GL-4 lube in it. The brass parts inside the transmission will last longer too. It takes some effort to find GL-4 80-90 sometimes, but it is out there. All older transmisions work better with something other than GL-5

Tom
 

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Registered
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Question? Can you just stick the hose for the pump down the fill hole and pump the old fluid out? Then reverse the prosess and fill it with new fluid?
 

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Opeler
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113 Posts
You can try. It's going to be difficult to get The hose to go where you want it to. You will never get all the dirty oil out either. But, it will be better than doing nothing.
 

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Not So Newb Anymore
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342 Posts
Another trick I used when changing the oil in my cars is to take a little extra clean fluid and before I put the drain plug in and kinda "flush" it out. This could help get out any junk in there. Also idk if they make one for the Opel but a magnetic drain plug would be handy.
 
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