1987 Transmission issues

[jeff eggert]

I have a 1987 that is having some slippage issues with the transmission. It is a L1T3 trans and when it is in or out of overdrive. I am curious as to if this could be a clutch issue or if there may be a problem with the actual overdrive itself. I don't want to go through the expense or time of putting in a clutch to find out it is an overdrive issue.

[c4c5specialist]

HI there,
First, I have never seen that designation of a transmission.
You mean a Nash 4+3??
If so, the overdrive unit will only affect rpms between engagement or disengagement.
The key is to turn the OD off, then see if the condition duplicates.
Otherwise, it may be the clutch.
More information would be helpful, like what gears this occurs, what loads and if anything recently has been done to the vehicle.
Allthebest, c4c5

[ChuckG]

If it is the 4+3, please describe the sounds it makes when OD is on and when it's off.

[jeff eggert]

Yes it is a 4+3, my son could not read my handwritting. It does it whether the overdrive is engaged or not. There is no distinct sound when the overdrive is engaged or if it is not engaged. The slipping is worse in the higher gears. There is no oil leakage. So a leaking rear main would not be the cause.

[c4c5specialist]

HI there,
If its any gear, most likely, its your clutch. The higher gears are more noticable from the increased load.
Allthebest, c4c5

[ChuckG]

My guess is the clutch and pressure plate too.

A failing OD has a distinct sound, oddly enough, made when it's switched off.

You're lucky. The OD is pretty expensive. I know!

[whalepirot]

Originally Posted by jeff eggert

I have a 1987 that is having some slippage issues with the transmission.

Is the engine RPM increasing with no increase in speed, or is this a perception that the O/D is slipping as it goes in and out of overdrive?