When i downshift my truck from fourth to third it feels like its in gear, then when i let out my clutch it grinds. My dad and i were sure it was the tranny, we put a different one in and it has the same problem. Does it need a new clutch? Can i drive it for a week before i fix it? Please i need all the help i can get. QUICK!

 

What kind of truck and tranny is it?

 

85f150 4x4 np435 trans

 

I run a 435 in my 250 as well. Let me get this straight. You can run through all of the gears and this problem only happens when you down shift?

You took another NP435 (known good) Tranny and put it into your truck and the exact same thing happens?

Then it ain't the tranny, and I don't see how it could be the clutch system if you can start it and drive it but not down shift. So you can shift the trans after you turn off the truck? It goes through the gears OK?

The only thing that I can think of right now that might be the problem would have to be in your synchros in the trans. But if you have another (known Good) Trans doing the same thing, then I do not know. If you can shift down, you can shift up too unless the trans is bad.

Now if you have a bad clutch, then it will be easier to shift up then down because you are going from a faster spin to a slower one. So if the clutch is not disengaging all the way during the down shift, maybe that will cause the trans to grind. Try double clutching it during down shift and see if that helps. If so, then you need to check your clutch disc and pressure plate.

Note: I often double clutch mine anyway, just because it seems to shift faster and easier that way. The NP435 is not forgiving. 1-3 are almost straight cut gears. If the sychros or clutch are bad, it will not shift.

 

Another thing i herd from my dads freind was that the shifter lever can wear and this would cause it not to shift into gear all the way when i downshift. But wouldnt this effect my forward shifts as well? I dont know...
What do you think i should replace first?

 

A HA! You did not say you were using the same shifting forks etc....YES! That can be the problem. The shifting forks move the gears forward and backward. Yes they can be worn on one side only. If they are bent, that can be the problem too. You would not notice the problem shifting in one direction but the other direction you would.

You can get a set of shifting forks through Bronco Grave yard fairly cheap and it is an easy fix. You don't even have to pull the tranny to do it. Yes I would start there.

 

Thanx for you expert advice. Ill see if that works. If it doesnt then you'll here from me here.
thanx

 

I'm no expert....Just voicing opinions. Hopefully helpful ones.

 

Well all i can say is that it didnt work. I got a shifter from the junkyard and no luck. The only thing left to try i think is to replace the clutch. I want to know if there is anything else you can think of. Im running out of options here.

 

[QUOTE=fids] I got a shifter from the junkyard and no luck.QUOTE]

A shifter, the thing you hold on to, or shift forks?

 

Check your clutch master cylinder mounting. My e150 flexed and I heard f series flexed too. The lost motion from the flex makes it so the clutch does not disengage. Hard gear shifts, hard to get into gear, grinding at points. Long shot.

 

Whats the difference between the shifter and the shifter forks? Is that the things that the shifter moves beneath the cover? That comes off wen you take the top cover off?
And i did check the posibility that the mounting could flex, it didnt move. But i will look again.

 

Fids,
The shifting forks are under the cover. The shifter moves the shifting fork assembly back and forth. The front fork shifts 3rd and fourth gear and the back fork shift 1st and reverse.( I think I said that right?) If those forks are worn on one side or bent in one direction, then you will onliy be able to shift one way without trouble. But coming back the other way will not shift properly. You have to pull the cover and inspect the forks. May not be easy to tell if you have not seen them before, so you should get a good set to compare to.