Hello - I recently finished my restoration project on my 74 model - manual transmission. I just went on a fun drive over the weekend (600 miles in the Texas hill country) and noticed I have a substantial transmission oil leak. I took a few pics this morning and assume it must be leaking from the passenger side output driveshaft. The oil is slung all over the place close to this output shaft. I don't think it can come from another place but want your opinions. And I assume this seal can be replaced with the transmission in place (will do both sides). I assume there is a front transmission seal where the motor crank mates to the tranny but don't think it can sling the oil like in the pics.

thanks for your opinions/suggestions

are you sure that is not Moly grease?
flung around by the CV joint...
did you use the paper gasket, or the RTV sealing technique on the half shafts?

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I don't' think it's moly grease. It really looks like 80/90 Weight oil. When I got the car, the tranny was low on oil, so I topped it off. This was my first long drive and it's all over the place now.

When I dropped the motor/transmission during my rebuild, I did remove the half shafts from the transmission (6 bolts if I remember correct). When I re-mated them, I didn't add any silicon when I bolted them back together as I didn't thing that was required. Was I supposed to do that?

So I am wondering if the half shaft to transmission output shaft requires a gasket or some kind of sealing (silicon or something)

see pic

Originally they do have a gasket there
I find RTV to make a much better seal than the original gaskets
but you need to buy new schnorr washers each and every time you remove the bolts
(its not worth the risk of them coming loose and destroying things)

I will admit that in the past I have just retorqued them every 100miles about 3 separate times.... but just buy the new lock washers and you won't have to live in fear.

So can the gear lube oil in the transmission actually come out through the center of the transmission output shaft and leak out between the two mating surfaces? The red line area in the pic I attached in an earlier reply. I figure the only way this gear lube could come out at this area would be a faulty seal on the transmission output shaft.

I recently created similar transmission oil leaks on my car. Replaced output seals and seated them too deep. Found this out once the car was back together and road tested

Replacing the seals with transmission installed is not a problem. Unbolt the inner CV joints, drop the axles down, remove the flange bolt and drive flange, you can then change the seals. Be sure not to make the same mistake I did, as seated too deeply, the seals will rub through and leak...I recognize the drip coming off your clutch cable pully & bracket. Good luck

Thanks for the reply - Does the drive flange piece have a gasket or does an RTV work to reseal it to the transmission body? On the drivers side, I don't see a flange so how is the seal on that side replaced? Figured I'd do both sides.

Try to clean the tranny as best as you can. Then you can monitor the leak better. Replacing the drive seals are not that hard. Be sure to get new scorr washers for the bolts. A seal puller from auto parts makes the job easier.

can't tell from pics, but make sure there is a clamp on both ends of the cv boot. there is a seal on the output flange and an o ring on the access door. i would start easy and make sure the cv boots are clamped and not slinging grease out. then go from there.

Other than using some form of gasket(s) which has been already covered, you mentioned topping the tranny fluid off. In some cases over filling could cause a leak because as the fluid heats up it also expands. If tranny is over full the fluid will find the "weak" spot and manifest itself as a leak.

My .02

to answer your question
no... the flanges are solid/sealed when installed
the gear oil can not come out from the center of the flanges
only from the seal on the outside of the flanges

although you would be surprised how much moly does come out of the mating surface to the cv. if you don't have gaskets in there, I would strongly expect that as a source of leak. you may have both leaking... but the CV gasket area (from your picture) always leaks first.

again, the gaskets are cheap
but the RTV works better than the gaskets


maybe do the outer seals/gaskets/fresh moly/ new schorr washers all at once.

brant

Thanks for all the feedback. Have several things to do and check. Should have this fixed shortly.

As for filling the transmission, I removed the top plug and with the car level, added gear oil until it came out of the hole, put the plug back. Isn’t this the correct way to fill the transmission? Hope I didn't over fill it with this technique....It has a breathe hole high up which would allow oil out if it was way over filled.

Could it be the orientation of your vent? Yours is turned. I have always made sure mine are like the picture. But I don't know for sure. This could be the dream fix...

I cant get the picture to load. Haynes maual page 87

Update

Last week, I cleaned the whole area where the oil was leaking. Ordered parts to do the output shafts, speedo cable etc. Got back from travel and oily again under tranny/motor area. So, it appears the rear seal on the engine must be the culprit. Checked tranny oil and its only a bit low, engine oil was about a half qt low. Damn. So now I am dropping the transmission to gain access to the seal on the motor. Will check out clutch plates as well.

Question on the final drive flange shaft bolt (output shaft that hooks to the CV joint of the drive shafts). In my Haynes manual, it shows a bolt (expansion bolt) that holds in the drive flange shaft. Does anyone know if these are 'normal' threads (counter clockwise to remove)?

thanks

There is a seal on the input shaft of the trans
Btw, hard to mistake engine oil for trans gear lube.

everything is apart. Leaking from both. Should be an easy fix and just hope tranny goes back in easy.

Most transmission oils will stink like rotten eggs. If it smells like oil, it's not transmission oil.

The vent (upper-right of your first photo) should have the hole pointing about 45 degrees to the right of straight forward; pointing it backwards definitely risks spewing gear oil out. Not sure about straight out to the side as shown in the photo.

Make sure what you have leaking, and check for where it seems to be coming from.

--DD

will correct the vent angle as you have pointed out. My manual shows a good picture. Thanks