Transmission won't shift into 3rd

[My49Plymouth]

Hi all,

I have a 1949 P-18 - with STD 3 speed. I bought the car last year and have never been able to shift into 3rd at speed.

It seems to shift smoothly into all gears with engine off. While at speed I can not shift it into 3rd - grinds. Then I can not shift back into 2nd - grinds - until I have slowed down quite a bit.

What is the most likely problem and fix? I would appeciate any assistance. The tranny is out of the car at this time.

I have an old Plymouth service manual but it is not very specific for troubleshooting. Sorry, if this has been covered here in the past, but I searched and couldn't find appropriate info.

[greg g]

Since the second to third shift is syncronized it would seem the problem lies there. The job of the sychronizers is to stop the motion of the gears on the shaft so they can engage. But they will not work if the input shaft is still spinning. A bit of clutch drag which allows the input shaft to rotate (or a burr on the pilot bushing) will prevent the syncros to do their job. But I would look for worn or broken sychro gears, and or the clutch drag situation.

Also what lube have you had in the trans. New oils made for hypoid gears have and anti shear additives that are corrosive to older brass and bronze (yellow metal) materials. If you had the fluid replaced with stuff for modern cars you might have buggered the synchro bits.

Never actually been inside a trans but when you drain the oil from the trans pour it through a screen strainer and see if there are any metal either white or yellow after the oil drains through.

[pflaming]

Greg: Will be draining the oil in my truck three speed. What oil do I put back in? Seems one should be carefull about oil in the engine then also.

[My49Plymouth]

Not sure of the oil - but it sure smells like 90W rear end lube to me. Pulled off the gearshift housing and stuck a magnet inside and did get some metal shavings - is that normal?

[greg g]

There was some discussion about transmission gear oil a while back. You want service rating 3 or 4 not 5 or 6. Try searching back during the aug through oct period.

[Captain Neon]

Sounds like you need a complete rebuild.