Gearbox question please

Not that good on Autos so here goes,

My mitsubishi chariot 1991 has auto with overdrive. Now in overdrive if i take a steady speed 1 st 2nd 3rd no problems. But if i boot it 3rd becomes a neutral, with OD off it's all ok.

Guess it will be an easy answer, but thought i'd ask before taking it in.

Thanks in advance

check the fluid level while engine is running and in park you could be low on oil or it may need a service

Transmission is basiacly due for overhaul overdrive is naffed
[overdrive doesn't work in 1 st and 2 nd]

OD works fine in 1st and 2nd.

Did think of that after posting, Will do on the weekend. Thanks

OD works in 1st and 2nd! Is it me or does that sound a bit odd, I always thought autos locked out OD until the trans was near or in top gear / range. Mind you I know next to nothing about them! Good luck though :)

I think they mean the OD switch is ON in 1st and 2nd (and even 3rd), but it doesn't mean that the trans engages OD in any of those gears until certain conditions are met (ie trans temp needs to be not dead cold, and road speed has to exceed approx 50km/h).

Anyway the issue is the overdrive clutch patch - a REALLY common thing to fail on that particular transmission (F4A21 or F4A22). The good news is it is really CHEAP to fix it. 3 10mm bolt are all that holds the end casing on, and with circlip pliers you remove the locking snap ring holding the friction plates in.

Go to a reputable trans place (I went to Marshalls in Hamilton) and got some new friction plates for approx $70-80. I believe there are 3 plates with friction material and 2 which are smooth. I ended up buying 3 of each and found I had the one plate left over.

I had the same issue with my old CB6A V6 Mirage with the same transmission, and it literally took me 15 mins and less than $80 to fix. I was told however that the piston and seal inside the overdrive hub wears out and they strongly recommended replacing them (at a cost of $200-300) but I opted not to and the transmission was still fine afterwards.

And the OD does not work until oil warms up/engine gets to operating temperature

While we are on Mitsi transmissions, I have a slightly different issue with a 95 Libero wagon. It slips between 1st/2nd and 2nd/3rd, not a lot but perceptible, can hear engine revs pick up briefly during change and then drop back as next gear engages. Its worse when cold. Has been doing this for around last 20,000 kms, it is gettiong very gradually worse.

My question is, is this a cheap fix or not - if it isn't its not worth doing as the car has 250k on it and its pretty rough, and I'll just drive the thing into the ground which was more or less my plan anyway. I reckon if I'm easy on it should get another 20,000 k out of it before it dies completely. Had the fluid changed a while back, made no difference

If pulling it out may as well do all thefibres & bandscheap as, if steels show blueing then replace them too .Helps to have a press as bloody hard to push the clutch packs down squarelyto put snap ring on .