A very leaky gearbox

[wdb]

I'm new to Caterhams although I did once own a 1966 Cortina GT (amongst a slew of other English cars back then). And I don't recall that car being as messy as this one. Just how badly do Cortina gearboxes leak? Mine appears to be leaking from the front, back, top and possibly also where the tailpiece bolts to the main box. It's coming out pretty well too; a 30 mile drive leaves a nice mess under the car. I cleaned everything off before the drive which is how I know it is coming out from several locations. Could it be overfilled? (Easy) Is there a breather on the gearbox somewhere? (Maybe easy) Is it filled with the wrong kind of oil that is foaming up and building pressure inside the case? I dunno. I can try changing the oil -- I'd love to hear what folks recommend to use.  

 

It's possible that it's leaking just from age. It was completely refurbished but it was quite a few years ago. The car had a total of less 100 miles on it since then, so it isn't an age/use thing, but perhaps the seals all deteriorated from sitting? Doesn't seem right to me, the seals don't look like cork or string or anything weird. Oh that reminds me -- there is some sort of black goo oozing from the rear seal.

 

Enough woe. Thanks for ideas and suggestions.

[MV8]

Should be 2.1 US pints (0.95 liters) 80wt. It could have something thinner in it to reduce parasitic loss for racing or an additive. I'd look for a vent on the tail housing in the web above the speedo drive.

[7Westfield]

if it's a type 3, the vent is top of tailshaft housing, left side, above the trans mount

 

[SENC]

If your gearbox is similar to this one from my 65 Seven, the blue arrow points to the breather bolt in one corner of the box cover - you may alternately find it on the remote connection to the tailshaft (I think this is the correct location, actually - my pic was a dry fit of final components to store everything in one piece while completing engine rebuild).

 

 

The red arrows point to common leak areas.  At the end of the tailshaft there are a few common reasons: 1 - the seal has become deformed where the yoke as put pressure on it sitting in one spot for an extended period; 2- the yoke itself is worn at the same spot as the seal hits; 3 - the bushing was installed incorrectly.  The speedo angle drive connection is another common weak point- could be a bad o-ring or missing gasket.  The biggest volume leak problem is often at the gearbox to bellhousing connection as one of the bolts (bottom left from the front as I recall, but could be right) enters a through hole into the gearbox (rather than a tapped blind hole as the other 3).  If this bolt wasn't installed with sealant, it will leak badly.

 

Hope this helps a bit, but (at least on my car) any of these would require engine and gearbox out of the car for resolution.  I would certainly try a complete drain and refill to see if it was just overfilled and being forced out.

 

 

Edited September 18, 2022 by SENC

[wdb]

Thanks for the replies. I may have found the vent. At least these pictures should help identify which gearbox it is. They also show the leaks.

 

EDIT: I also checked for overfill. The level is well below the edge of the fill plug so my assumption is no, not overfilled. As for the apparent solution, pulling it out and reasealing it -- is it only possible by pulling the engine, or can it be snuck out the bottom? Seems pretty tight under there.

 

 

Edited September 18, 2022 by wdb

[wdb]

Here's one more, showing the end of the tailshaft from above.

 

 

[MV8]

2000E/ "Bullet": https://www.burtonpower.com/tuning-guides/tuning-guide-pages/ford-2000e-bullet-gearbox-guide.html

Looks like all your leak is from the front around the input shaft. I suggest pulling it to replace the seal. You could pull it and with the slip yoke installed, use a rubber tip air nozzle to blow a little air into the vent and enjoy the show in the bell. May be leaking around the rails.

Edited September 18, 2022 by MV8

[SENC]

A different gearbox from mine, but looks like similar failure points.  It appears the rear seal has failed and a piece is falling out below the yoke.  You could, conceivably, pull the yoke and drives haft out the back and replace that seal, but it would be tough - and given other apparent leaks it would probably be best just to pull the engine and gearbox entirely.  I'm surprised there isn't something covering that vent hole - conceivably you could have oil getting flung up that hole and then dripping down the sides rather than additional leaks.

[wdb]

It is leaking out around both top covers, at the tail housing mount to the gearbox, plus you can see those wet spots at the bolts holding the bell housing. (There is no oil dripping out at the front edge of the bell housing.) That's why I was thinking it was pressure buildup. The stuff at the rear seal is gooey. I don't see oil there. I agree that if that little orifice is supposed to be the vent, it needs an upgrade.

 

I am resigned to pulling the engine on my brand new purchase, but it will wait until cold weather forces me off the road. It is an intoxicating thing. I've already nearly doubled its lifetime total mileage.

 

Thanks for all of the advice and links. I'll try to post some good news too.

[MV8]

I don't think the vent hole is too small but it my be blocked internally. Blow air into the filler port and feel for a breeze at the vent. You may be able to remove the vent cover with the trans installed.

 

I'm thinking the front face of the main case is leaking into the bell mating surface. If the vent is clear, maybe there is no gasket at the bearing retainer.

 

Since it is low, you might as well pour it out and compare the flow/thickness to the 80wt going back in.

 

You might also spray a little ospho or other phosphorus metal prep underneath to stop the bare metal from rusting, let it dry, then rattle can rustoleum clear so it wont be solid rust by the end of the season. Nice thing about matte clear is you can't see the overspray or just spread the leaked dope all over until you can deal with it this winter.