NP435 Problem
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Elder User
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NP435 Problem
I have an '85 302 4x4 with the NP 435 4-spd. The truck shifts fine when it's cold; but, when I drive about 5 miles to warm it up, the transmission starts to shift hard and grind the gears when shifting down. Sometimes, when I stop, it sticks in 4th gear and will not shift into first.
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Joined: Apr 2004
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You symptoms are slightly different than the usual clutch issue, BUT:
Check your clutch pedal, linkage, master cylinder & mount for flex. Firewalls in '80s trucks rusted, cracked, flexed or all three.
If your master is moving, you'll need to reinforce the firewall.
Other issues with these could cause a loss of clutch action at the pressure plate.
Check your clutch pedal, linkage, master cylinder & mount for flex. Firewalls in '80s trucks rusted, cracked, flexed or all three.
If your master is moving, you'll need to reinforce the firewall.
Other issues with these could cause a loss of clutch action at the pressure plate.
Hotshot
Joined: Oct 2002
Posts: 18,488
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From: The Big, Oregon
I'm going to guess the fluid in the clutch system is old, and has absorbed too much water. I have this problem with my Courier time to time, when it gets hot the clutch won't release. The pedal feel doesn't change that much when this happens.
I would flush that out first, especially if the fluid is black, and then see if it still happens.
I would flush that out first, especially if the fluid is black, and then see if it still happens.
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Thanks - I'll flush the clutch system - the petal pressure seems high - I'll start with inspecting the back plate for flex and flush the old fluid out and see what happens.
I'll also change the oil in the transmission - that can't hurt - I suspect it's 23 yrs old.
I'll also change the oil in the transmission - that can't hurt - I suspect it's 23 yrs old.
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Joined: Sep 2007
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Does the clutch pedal get soft after the 5 or 10 minutes?
BTW, use what fluid you want, but I will say (maybe I've said it too much) that I really like the Mobil1 75W-90 that I put in my NP435. Tons better than whatever was in it before... which I suspect to have been ATF, which these transmissions did not call for.
BTW, use what fluid you want, but I will say (maybe I've said it too much) that I really like the Mobil1 75W-90 that I put in my NP435. Tons better than whatever was in it before... which I suspect to have been ATF, which these transmissions did not call for.
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