NP435 4th gear coast chatter

XJsavage

XJsavage

CounterCulture
Joined
Aug 15, 2009
Location
Lyle's Ford SC
Background:
4x4 model Ford wide ratio NP435 junkyard pull out from a '78 F150 (300I6)

It's currently mated to a 5.3 litre GM. I've put several thousand miles on it so far and I run typical GL5 in it.
It doesn't happen all the time, but usually when it's warmed up, it'll make a chatter sound on deceleration or coast, but then goes away when under power. I'm running single Ujoint 1410 driveshafts that aren't precision balanced to be honest. The angles at the tcase and differential are fairly close to the same. I can throw in angle finder results if that data would be useful. The Np205 behind it was recently rebuilt.
I'm trying to get to the bottom of what causes chatter in these older manuals, whether it be failing synchros, worn bearings, incorrect fluid or whatever. I'd rather not spend all weekend pulling it out if I don't have to.
 
XJsavage said:
Background:
4x4 model Ford wide ratio NP435 junkyard pull out from a '78 F150 (300I6)

It's currently mated to a 5.3 litre GM. I've put several thousand miles on it so far and I run typical GL5 in it.
It doesn't happen all the time, but usually when it's warmed up, it'll make a chatter sound on deceleration or coast, but then goes away when under power. I'm running single Ujoint 1410 driveshafts that aren't precision balanced to be honest. The angles at the tcase and differential are fairly close to the same. I can throw in angle finder results if that data would be useful. The Np205 behind it was recently rebuilt.
I'm trying to get to the bottom of what causes chatter in these older manuals, whether it be failing synchros, worn bearings, incorrect fluid or whatever. I'd rather not spend all weekend pulling it out if I don't have to.
Click to expand...
Since no one else has replied yet with anything useful..... an old trick... Throw in some sawdust, or you as you may know it, a McChicken. :D
 
Kamel said:
Since no one else has replied yet with anything useful..... an old trick... Throw in some sawdust, or you as you may know it, a McChicken. :D
Click to expand...
Ah don't remind me. I was at monster truck show/Upchurch concert last night and ended up leaving after an hour when I saw a whole squad that would probably recognize me on the spot. They were there as security. Nope nope nope.

Yep, I'm taking the transmission apart today.
 
In for what you find. What is chatter?
 
I found more or less nothing. I just drained the old GL5 and dumped in a gallon of 75-90 full syn. Took it for a 30 mile test drive. Seems way better.
IMG_20210418_101532868.jpg
 
I think it's just inherent in how they're designed and assembled. They're a truck transmission after all. Basically industrial. Not super refined. Just heavy and strong!
 
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