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'88 4 speed auto: 4th gear sluggish

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i am the second owner of my '88 and it is my first vehicle. it has a L4N71B 4 speed auto that leaks fluid and i refill the transmission every couple of weeks. i figure that this is a cheaper solution to this problem than to dismantle the transmission and diagnose it myself (i also lack the equipment to raise the car at home) or take it to a shop and potentially feed me information that i likely don't need knowing.


i believe at one point it was driven with low fluid that potentially brought damage to the trans' components since, recently, i discovered that the gear for 4th may be worn down. when it switches from 3rd to 4th, the engine rotates higher by around 300 rotations and slowly drops down, as if it were shifting in slow motion. none of the other gears seem to do this but it does make me wary and i make little money. fortunately, i do not drive this truck often at speeds which require 4th gear. however, i hear no strange, scary sounds or feel any strange motions when it shifts at this speed, or for any other drive gears, so i suppose for now that it's not any more serious than it could be, but i may be wrong. i guess it's also worthy to note that i'm in the colder season where at night it's around 40F at night, which is when i drive it home from work (i know not to press the gas down too much at these temps until i know the engine's warmer; older vehicle!)


i've poked around with google searches, came across forums (some with disrespectful exchanges lol) and blog entries alike, things about clutch plates slipping and checking the fluid color. for the sake of mentioning, the fluid color's been ok but then again i do refill it periodically so it's probably not a worthy diagnosis with my application.


i could upload a video demonstrating the performance if it will help! however, young person on their phone while driving and all that. no fancy airbags to save me.


take for note that i have little mechanical experience and the most i've done with the transmission is removing the oil pan and replacing the gasket and fluid filter, with the aid of my stepfather, who only knows maintenance for '80s and '90s ford F-series pickups while growing up in kansas.


this may be one of those posts that could be limited in help given my lack of expertise, so i'm mainly posting this for the sake of opinions as to what could be done or improved, even if it could be costly, or if it's not something to worry about too much (very unlikely with the latter as in my opinion any issue left unchecked could bring disaster over time). any little bit of info helps and i'd love to hear it from those who know these vehicles much more than i do. thanks for your time

Edited by fleenz

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