Hello

I have a 1990 F150 w/ a 300 inline 6. The truck runs great. Once the weather gets over 75 degrees I have an odd transmission problem. When I'm at constant road speed, say about 45-70mph, its like the transmission slips into neutral for about 1/2 - 2 seconds. The engine revs up. I let my foot off the gas and the engine comes back down and then the transmission re-engages. If I don't let off the gas, the engine will rev The trans fluid doesn't smell burnt. The fluid doesn't look dirty. The fluid level is full. I turned off the overdrive button and it still does it. This happens probably once every few days. The transmission shifts really well. Its smooth, but you can feel it shift. Feels pretty normal except for the neutral drop issue. Anyone have any ideas what's going on???

Thank you
Kevin C

 

Try changing the fluid and filter. The filter may be clogging up.

 

Yes change the fluid and filter. Also this may be in part heat related, the radiator cooler tends to become less effective over time. If the radiator fluid has been allowed to get old from time to time you can get build up on the inside. I would add a cooler that is big enough to cool the trans by its self, but still loop it with the raidator. Hope this does it, a transmission on these old trucks can run more than the truck is worth. If you keep having trouble take it to a good shop, problems only get worse, I would hate to see you burn up a trans when it could have been avoided.

 

Thank you for the responses. I'll start with the trans fluid and filter. I have a pan leak anyhow so it will be nice to clean that up as well.

Thanks again,
Kevin C

 

Hello,
Just wanted to give an update on my truck. This weekend I replaced the transmission filter. As much of a mess it made on the driveway I’m glad I did it. Looking at the old filter in comparison to the new one, the wrong filter may have been in the truck. The new filter is about ¾” taller, therefore sitting deeper in the transmission fluid. Maybe the old filter wasn’t deep enough so it was pulling air thru the system causing a feeling like the truck was shifting into neutral. I drove the truck quite a bit this weekend and the problem wasn’t there. Hopefully that took care of it. Thanks for the advice.
Kevin C