MGB 1970 Automatic problems

[Hersheymad]

Hi,
Can anyone help, I have a MGB AUTO 1970, Im just running her in with new a secondhand gearbox without history, the problem I am having
is that altho the gears are quite smooth, Im having a problem hitting top gear, the engine seems to resist going into this gear and pops back out,
Any suggestions please I have lookt for info on autos without much success thank you Pam

[suffolkpete]

Sounds as if the kickdown cable is incorrectly adjusted. The forum Borg Warner expert Harvey will no doubt be along soon with other suggestions.

[harvey]

Low fluid level can cause it to drop out of top, how are you checking the level?

If the kickdown cable is set too tight it will make the upchanges late to the point where you have to lift off the throttle to prompt the upshift, but that will affect the 1-2 shift, as well as the 2-3 shift. Once TOP is engaged it shouldn't drop out, or change down unless your roadspeed drops significantly, or you use kickdown.

Re-reading your post here (and elsewhere) it's possible it could be a linkage problem as well, in that when you think you're in "D" you're actually in "2", and when you do get TOP in "D", the linkage being incorrect pulls it out and back into "2" again.

[Hersheymad]

Thank you again for the reply, will check, didnt realise too that so much help was available. Brilliant

[Hersheymad]

We are checking the fluid with the engine running altho we have been told that maybe this isnt helpful as the fluid tends to slosh about giving
an incorrect reading ?, but we have checkt the fluid both ways running and idle and its up to the marker, we do think it is the cable as we had to
change it,

[harvey]

We are checking the fluid with the engine running altho we have been told that maybe this isnt helpful as the fluid tends to slosh about giving
an incorrect reading ?,

It should be checked HOT, on level ground, and running in PARK*. If you're having difficulty seeing the level rub some blackboard chalk on the bottom of the dipstick, and then wipe it all off, that will make the stick nice and dry, and so a lot easier to see the level. Most of the problems on those boxes are fluid level/selector linkage/kickdown cable related, that's why all three of those should be checked and sorted before moving on to anything else. If the problem started after you fitted a selector cable, then that's where I'd be looking.

* For the whole procedure:

Firstly check that the selector linkage is correctly adjusted and is working as it should.

Then check the fluid level as follows:

With the transmission at normal working temperature, the engine idling, and the car on level ground, run through the entire selector range allowing a few seconds in each position to allow it to engage, starting and finishing in PARK, then, with the engine still running walk round remove and wipe clean the dipstick and re-insert to take a level. You will have time for a few quick dips to try and get an accurate level. If you add fluid repeat the whole procedure before taking another level. Use only ATF-G or fluid that meets Ford spec. M2C-33G. DON'T use any of the DEXRON type fluids. A small amount of white blackboard chalk rubbed on the bottom of the dipstick, and then wiped off, dries it and makes seeing the level easier.

The fluid should be red and clean, not brown and burnt.

Check the condition and adjustment of the kickdown cable.