MGB Gearbox whine

tetlow · Post by **tetlow** » Thu Jan 18, 2007 9:37 pm

I have a std 4 syncro MGB box on my V8.
It was recently rebuilt after 3rd broke.
It has a low whine at high speeds when not under load.

This noise does not sound at all terminal and I was wondering if I have used the correct oil. I have used 20-50 classic castrol, same as the engine.

Is there another oil or additive that would reduce the noise?
Regards
Dave

JSF55 · Post by **JSF55** » Thu Jan 18, 2007 9:50 pm

Would have thought EP80 for a gearbox, 20/50 is a bit marginal, best check the manual, john

tetlow · Post by **tetlow** » Thu Jan 18, 2007 9:57 pm

I have looked in the manual.
The recommended oil is 20-50 GTX the same as the engine.
I wonder is the extra torque from the non standard engine is causing noise that I hope I can reduce.

Dave

mgbv8 · Post by **mgbv8** » Thu Jan 18, 2007 9:57 pm

Yep
Deffo EP 80 or 90 for an MGB V8 diff mate. Plus a bit of Molyslip if its a tad worn.
Perry

tetlow · Post by **tetlow** » Thu Jan 18, 2007 10:00 pm

Hi Perry
Its the gearbox not the diff.

I believe you have an auto box. I would love to do that or at least fit a R380 but the dosh has finally run out.

Dave

mgbv8 · Post by **mgbv8** » Thu Jan 18, 2007 10:01 pm

Sorry Dave
Thought you were talking about the rear axle.
Yes, 20/50 is what the MGB V8 box should use. Mine lasted very well on it before the Chevy conversion. There are some who actually use ATF in the MGB V8 box though.
Mine used Halfords 20/50 classic with no probs. And that was on the drag strip.

tetlow · Post by **tetlow** » Thu Jan 18, 2007 10:10 pm

Cheers Perry
I will have to put (my new £500 roof, the reason I can't afford a new box) down all the time now so I can't hear the noise.

Dave

davemgb · Post by **davemgb** » Fri Jan 19, 2007 6:56 pm

It is regularly suggested that the V8 version of the MGB gearbox be filled with EP90 oil to protect against the high torque transmitted.

Dave

mgbv8 · Post by **mgbv8** » Sat Jan 20, 2007 6:46 pm

Dave and Dave
I think some MG people do use ep oil their boxes. But I think it can give problems in cold weather. Quite a big discussion over the years on the MGOC forum.
And we have a couple of resident oil experts who give the pro's and con's of all our oil queries.

JC. · Post by **JC.** » Sun Jan 28, 2007 5:35 pm

If you compare the parts list for the V8 box and the B box, it is essentially the same gearbox, all be it with a different ratio 2nd gear , installed in a different casing.
The V8 box was filled from the factory with ep90 and the 1800 box with 20w/50.
Given this information, it is conceivable that it would be a good idea to run ep90 in the the 1800 box when mated to a V8.

Your system will be quite unique. The block will have been modified slightly rendering the engine suitable only for this application. So, unfortunately for you changing to another type of gearbox is not an option unless you want to buy another engine too!

The way the V8 mounts to the B box in this application is quite interesting. There will be an adapter plate between the box and the engine. The flywheel will be from a B series and it will have been milled out significantly to take an MGC clutch assembly.

Im not suprised you are going through gearboxes quite quickly. The BV8 box was right on the edge of its power with a detuned 137bhp going through it. I know of one MGOC member who's car has been through no less than 5 BV8 gearboxes in its life!

That said, B gearboxes are cheap. You can pick them up on eBay for £25 or so? Ultimately you will just be throwing good money after bad.
Would suggest you think about looking for a new engine and a 2wd LT77 box for when the 1800 box eventually and inevitably goes poof.

Best,

Jon.

tetlow · Post by **tetlow** » Sun Jan 28, 2007 9:57 pm

Hi Jon
I have exactly as you describe, Adapter plate and MGC clutch.

I have a second gearbox with the necessary shortened input shaft.

After all the advice I have received I am now looking for a 4.0 + R380, and hope the engine/box I have lasts long enough to sell on Ebay.
Thanks for the help.

Dave

mgbv8 · Post by **mgbv8** » Sun Jan 28, 2007 10:13 pm

Or buy an adapter kit from D&D and shove a Chevy TH350 3 speed streetfighter autobox in.

JC. · Post by **JC.** » Mon Jan 29, 2007 2:32 am

mgbv8, I hear the sprag clutches in those gearbox's don't last too long?

ian.stewart · Post by **ian.stewart** » Mon Jan 29, 2007 10:09 am

Theres no problem withe the TH350, its been about for years.
Back to the original post, Noisy gearbox, Normally once the noise is noticable, tne damage is done, you could try EP90, which is thicker and may quieten the noise and make it drivable. 20/50 seems a strange choice for a gearbox it has no pressure addatives to maintain the oil. thats what the EP stands for, Extra Pressure,
Now heres a question for the MGB owners, why do MGB owners who have converted to V8s have a fixation on using the the R380, They are EXPENSIVE, Hard to find and easily confused with its older brother the LT77, I would be using the LT77, there are plenty of people on this site using LT77s and giving them SERIOUS abuse, the Axle will give out before you break the gearbox, and MGBs have issues with getting plenty of sticky rubber under the arches, so you have a safety valve built into the system to protect the axle and gearbox, Fit a LT77 its cheaper, you wont break it, especially if you have been using a MGB 4 speed, I think the old P5 boxes were based atound the B box, and Nobody will use one of those cos they are fragile.
Ian

tetlow · Post by **tetlow** » Mon Jan 29, 2007 1:45 pm

Thanks Ian
I was told the R380 was better than the LT77 but considering the costs the LT77 does seem the better value package.
I am also very interested in Perry's route and fit a auto box.
I doubt that many complete systems come up for sale though as I do not want the hassle of building one up myself

My existing box is not too bad, but I think I will fill it with EP90 anyway.

Dave