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MG MGB Technical - Buying an MGB GT Automatic

I posted this on MGB general too as I'm not sure which one is most appropriate, I normally post on the MGA forum, but am now planning to buy an MGB GT automatic for my wife. I have found a few potential cars to look at and would appreciate any advice on buying.

I have plenty of (mainly MGA) projects to keep me busy, so I want a reliable, restored car in excellent condition. I know these cars fairly well as I restored a 1976 GT for my brother some years ago, but I have no experience of the auto box. I checked the archives and there is lots of positive stuff there, but are there any drawbacks or pitfalls?

Any feedback would be much appreciated. Thanks, Neil
Neil McGurk

The MGB used the BW35 which has been used in dozens of marques and models and millions of cars. It is very reliable, and there should be still plenty of people around with experience if it *does* need work at any time. It might have been rare in an MGB but in itself it is neither rare nor exotic.
Paul Hunt

Neil ,The bw 35 is a well proven design based on the origonal BW 8., a cast iron box found in early Studebakers and Ramblers etc. Its' weakness has always been the reverse band as the servo appling it is bolted to the case by two bolts. There is a lot of leverage on these bolts. Any delay when selecting Reverse almost always means an overhaul. Adjusting the band is just a band aid. Any squak ,slight shudder on the one two shift, medium throttle upshift, also means an overhaul. The foreward drive clutch is worn out. Always pull the sump and check for friction debris, the death rattles. A little amount of brass filings , ie glinting in the sun light is the norm.
For the little lady driving, make sure that the fast idle cold is around 1200 rpm before selecting Reverse, also that the car is stopped , not still moving foreward. The oil pressure in Reverse is around 200psi and foreward around 150psi full load. Having said all that the transmission in good condition will last a long time if serviced every 2000 miles. Sean
S Sherry

Neil, service at 20,000 not 2000. sorry Sean
P.S. the most important adjustment is the cable connecting the carb. linkage to the transmission. It controls the line pressure and the upshift points. The band adjustment stays fairly stable if the line pressure is set correctly via the cable. Incorrectly known as the kick down cable. If all else is correct and the kick down doesn't work the problem is in the linkage. Check that the carbs are getting full throttle etc,.
S Sherry

Anyone know an approximate cost of overhauling one of these boxes?
Neil McGurk

Find a local auto specialist and ask them. It's a reasonable question if you specifically need an auto box for any reason, in which case you might choose to purchase one that is showing problems knowing that you will have to get it repaired. Someone else may choose to keep looking until they find one that is working as it should. There is no point someone many miles away (even less the other side of the Atlantic) giving you costs if you are unlikely to be able to get it repaired there. But I'm pretty sure the answer is going to be the proverbial piece of string - it all depends on what is wrong with it. The stresses in an auto box are much more balanced than in a manual, everything happening around a single shaft, unlike having to switch between shafts in the intermediate gears of a manual.
Paul Hunt

Neil, any companent transmission shop could overhaul a BW 35 with their eyes closed. It is no big deal. In low horse power cars there should be no hard part problems. In Australia they stuck them behind four litre engines ! Usually clutch plates,a rear band and a seal kit will sort them out. Also a torque converter flush. They have a machine to do this. Sean
S Sherry

The BW35 was used in the FX4 Black Cab so you are assured of decent parts availabilty and reasonable repair / overhaul costs if you use a autobox specialist that is recommended by your local taxi drivers.

Paul Humphries
Paul Humphries

Thanks everyone,

Bought the car and the gearbox appears to be perfectly fine! Smooth changes and goes into reverse instantly!

There is a box (full conversion kit!?) on eBay right now, but so far my confidence is high!
Neil McGurk

This thread was discussed between 11/09/2008 and 05/10/2008

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