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MG MGB Technical - Late Model Gearbox

I have an 80 LE and have spent much of the last year and half since I bought it replacing deteriorated rubber and other gaskets. Most of the engine leaks are fixed (new head gasket, pan gasket and more). I also just rebuilt the clutch and slave master cylinders which eliminated a brake fluid leak. However, there is still oil under the car, but now I've isolated it. It's coming from the front of the manual gearbox, running down the clutch lever and dripping off the clutch slave cylinder and soaking the undercarriage from there back. Now here's my question. It's a clear, thin fluid and odorless (unlike motor oil). I thought these transmissions ran 20w/50w motor oil? I plan to drain it and refill with motor oil, but wanted to know from some of the experts if another oil was used in these gearboxes other than what Haynes manual recommends. I'm hoping that the leak is mostly from the thin oil and changing to recommended 20w/50w will stop or significantly reduce it. Let me know if I'm making a mistake here.
Rick Penland

Rick, you are correct in that the gearboxes use 20w50 engine oil. The only other fluid I've used is ATF to clean the overdrive unit. I used this for quite a while but got tired of the leaks (due to ATF being thinner it leaks worse than engine oil but with it's red colour, it's easy to see).

I've tried to correct the leaks (new gaskets, seals, silicon) but now just live with them.

Based on your description of the fluid leaking from your car, sounds like it may be clutch fluid. I'm only guessing due to the route travelled by the fluid. You say you've fixed the brake leak so can't be that. How is the level in the clutch master? Oil/fluid leaks have a nasty habit of starting far from where you actually see them.

Hope this helps. You won't be making a mistake putting 20w50 in the 'box.

Cheers
Simon
Simon Austin

Simon, your note of ATF fluid used to clean the overdrive unit is of interest. I'm a little puzzled about this car and have no history on it, but note that the engine is 18V884. According to what I can find, the 884 was an overdrive mated engine, but the transmission doesn't have an OD unit. Thus, it might have been removed at some point, but someone replaced with some sort of odd fluid. The clutch system is working perfectly now with no loss of fluid so I'm convinced it's following from the front of the transmission out the shaft and dripping off of the slave cylinder. The dust cover for the clutch shaft is missing and I'll order one of them, but need to slow or stop the fluid leak. The fluid is clear and odorless without the typical petroleum smell of motor oil. It may be some sort of hydraulic fluid and I have no idea what it's doing in the transmission. Transmission shifts fine with no noises and hope this odd fluid wasn't a coverup for some sort of transmission problem.
Rick Penland

Rick

Have you drained/siphoned a sample of the transmission oil to verify that what you are finding on the floor is indeed identical to what is in the tranny?

FWIW

Larry
Larry Hallanger

Rick. There are three possible sources for a fluid leak in that area--front seal on the transmission, cluch hydraulic system and rear main seal on the engine.

Without a Heritage certificate, it is difficult to know how your car was configured as it left the factory. The fact that the identification number on the engine and the type of transmission that is installed only indicate that one was probably replaced. It is also possible that both are original to your car and that an "overdrive" engine was mated to a non-overdrive transmission at the factory. Standard build time seems to have been about two days and, if the car was to be built with a four speed tranny and only the 884 engine was in stock at that time, it is possible they installed that engine rather than remove the car from the production process and wait until a shipment of 883 engines arrived.

As to fluid, motor oil is the recommended product. I, too, have used ATF to help clean out an overdrive transmission and it worked just fine. But, I was advised to only run it for 1,000 miles, then, switch back to motor oil. As to the weight, the various multi-grade oils work fine. So does SAE 30 motor oil which, at one time, was the recommended fluid.

Les
Les Bengtson

Les, thanks for the insight on the 884 block. I've never been able to determine what difference there was in the 883 and 884. Moss catalog production notes indicate the 884 was for overdrive (Haynes doesn't differentiate the two), but it seems reasonable that it wasn't necessarily always fitted. I haven't ordered the Heritage certificate (spending money on parts), but will do so eventually. Given the mechanical condition of the car, strong, but obviously sat unattended and likely let sit outdoors for a long time, someone may have put a lighter oil in it to clean it out or loosen it up and subsequent owners weren't informed. I'll try changing it this next week to 20w/50w Castrol and watch for metal in the fluid.

That brings up another question, there is no dipstick that I can find and two "plugs", one on the bottom and another mid way up the passenger side of the transmission. I assume the upper one is for filling and it appears that about 2 3/4 quarts is correct per Haynes. Doesn't look easy to fill without some ingenius way using a hose or such.
Rick Penland

Rick, you fill thru the side plug until it reaches the plug opening (just like a rear end). A lever type pump oil can with a hose on the nozzle works well for filling.
John H

Rick,

Make sure the filler plug is removeable prior to taking the drain plug out.
Roger T

Rick. John and Roger are correct. The oil is drained from the hole at the bottom and refilled through the hole in the top. Draining the oil before knowing that you can get the upper plug out is a very bad idea. They use the same size wrench which, from memory, was 3/4".

As to filling the tranny, this is a bear if you have to do it on the ground or up on jack stands. I purchased one of the hand pumps which screws onto an oil bottle (costs about $4 at most parts stores) and use it to pump the oil in. Much faster than using a pump type oil can. Even with the pump attached to the oil bottle it takes about 100 strokes of the pump to empty most of a one quart oil bottle. Then, you empty the second bottle as much as possible. Then, you pour the oil from the first bottle into the second bottle and pump some more. When it quits pumping out, you start on your third bottle and pump until the oil is flowing out of the hole. Sit back, let the oil drain onto an pan or some such, wipe the left over oil off the side of the tranny and reinstall the filler plug.

They also make an oil suction gun which is much faster than the pump on the individual oil bottles. Slightly more expensive too. Since this is something which is only done rarely, I have gotten by with the pump on the oil bottles.

Les
Les Bengtson

Rick,

Like Les said it takes a lot of strokes to fill the gearbox with one of the small pumps. And doing it on your back under the car supported by jackstands)is extremely uncomfortable.

So much so that I made a simple pressure system out of the plastic quart bottles that the oil (20w-50) came in.

I got some small clear plastic tubing 3/16 inner and 5/16 outer. About 5 feet of it.

Drilled 2 holes in the plastic cap of the oil bottle. The holes were 1/4 inch and then I just wiggled the drill bit around a little. I wanted the hose to fit snuggly into the holes.

I cut the hose. One hose was about 18 inches long. I pushed it about 1/2 of the way into the bottle. The other hose was about 3 feet long. I pushed it all the way to the bottom of the bottle.

Then I put a small fitting on the first hose to connect it to my air compressor. I adjusted the pressure to about 45 lbs.

I put the other end of the longer hose (the hose that was pushed all the way to the bottom of the bottle) into the side fill hole of the gearbox. I then set the bottle on the ground under the gearbox hole and held on to it. Then, I squeesed the trigger on my air compressor hose and let it flow. The air pressurized the bottle and pushed the oil into the gearbox in about 2 minutes.

Then, I simply changed the lid to the next bottle and repeated the process until the oil started overflowing from the hole. It was much more easy on my body even though I still had to be under the car to hold the bottle and operate the trigger.

Cris
Cris DeYoung

Cris. An old dog has just learned a new trick. Thanks. Les
Les Bengtson

One of the best tools I purchased after getting into the fun of MGB's was a small rotary pump that fits onto any drill. It uses standard garden-hose-type thread on fittings to which I attached lengths of clear, plastic tube of sufficient length.

I throw the inlet hose into the can of oil, outlet into the fill hole and spin away! It only takes a couple of minutes at most to empty a litre.

I picked up the pump at a local auto parts shop. If anyone is interested, I'll get the name of it and pass it along.
Simon Austin

Les,

I've learned so much from your posts I'm just glad I could return the favor in a very small way. The 1st time, I was a little worried it would burst the bottle, but I 've used this on several cars and several different types of oil and so far no broken bottles.

Cris
Cris DeYoung

Well, you guys are really ingenious. That's part of the fun of these cars is figuring new ways to do things. I have one of those pumps you use for fish tanks and don't have a fish tank any more so thought I might add some hose length to each end and press it into service. Thanks for your thoughts about making sure both plugs can be removed. Heck of a note to drain it and realize you can't fill it back up. Thanks, guys.
Rick Penland

I go to K-Mart and for $5.95 buy a small hand held plastic garden sprayer. It holds one quart. Remove the nozzle and fit a 5/16" plastic hose to it. Put in oil-pump it up and fill anything. I use one for bleeding brakes and also use a large one for priming new engines prior to starting. These units are a godsend as they work clean.
Sandy Sanders
Hudson Florida
Sandy Sanders

This thread was discussed between 07/06/2006 and 10/06/2006

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