Just got back from taking the Bronco to Steamboat and back and noticed a clunking sound when I start off in 1st (not granny) when i got back. It seems to be coming from the clutch/trans area as it goes away when I push the clutch in.

Its like a rotating clunk.. not just one. Clunk, Clunk, Clunk, Clunk, getting faster as i speed up then it seems to go away above 10 or 20 mph... maybe it gets too fast to notice or goes away.. not sure.

I thought maybe it could be the rear drive shaft however since it goes away when I push in the clutch and since I am a novice when it comes to manual transmissions I wanted to see what others thought.

I have one more run to make to Colorado Springs this week this before I start the trans swap.. but wanted to get some idea of what it could be as I really dont want to crawl underneath it yet if I dont have to... but I dont want to have the thing blow up on the way there and back...

Since everything else on this truck was loose from the PO I just assume something was not tightened or put together correctly in the transmission, clutch or throwout bearing... I wouldn't' be surprised if its the Dana20. These are the last few things that I haven't touched or fixed yet and so pulling them apart was going to be on the list regardless of hte ZF-5 swap...

Is there any kind of inspection hole on the setup?

I had a bolt connecting the driveshaft to the t-case yoke loosen up on me. I had an intermittent clunking on acceleration. At the time, I thought it was my new Lock-Rite acting up, but it was the loose bolt.

Check the simple stuff first.

ya iam going to take a gander today and check all the yokes/driveshaft bits..

Maybe remove each driveshaft separately and take short test drives in between each removal. Eliminates the possibility of them and makes sure once your trans swap is complete those parts are good to go.

Check you u-joints in both driveline s.

All the ujoints and cap nuts are all tight. Wiggled the rear drive shaft and it does move a little in one direction at the CV joint - more than It should I would think...

I don't see anything else that would cause the problem and now that I drove it a little more today it really feels like the rear driveshaft as my vibrations are more pronounced than I remember.

I can take the shift fork boot off the bellhousing but i have no idea what Iam looking for as its really hard to see in there...

Here's a video of me wiggling the rear drive shaft... hard to see the movement unless you look closely.



I guess it really doesn't matter as long as this thing stays together for another 175 miles as I was going to have a brand new rear shaft built, new clutch and throwout bearing put in among other things.

That is a fair amount of movement & likely the noise at low speed/rpm. You are twin sticked right, throw it in FWD, drop the rear driveshaft & see if it still makes the noise. On second thought, you don't need twin sticks. Throw it in 4WD high and drop the rear drive shaft.

When you do your trans swap you can get the cardan joint rebuilt since your driveshafts will likely need mods.

no twin sticks right now, but i will drop the rear drive shaft. Just drove it again and its pretty bad.. lol

Ive had a bolt on the flywheel back out before as well. Made a pretty noise

Throw-out bearing is my guess. Put the t-case in neutral and put the tranny in gear and let the clutch out. Does it still make the sound?

Ah good idea will do that today


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Well I decided not to drive it to the springs so I will be pulling the bronco into the garage today and start to strip it down to get the trans swap started, but before I do I will try the neutral trans in gear thing and see what I find out.

I wont be reusing anything from the NP435 and only using the flywheel and centerforce clutch pressure plate off the back of the 400 but would be nice to know all the np pieces are sorted as I will be selling it all after the swap is done.

Im a fan of the throw out bushings for this reason.. those bearings are terrible

Its definitely the rear shaft.. pulled it into the garage this afternoon and Kinder helped me start tearing body parts off to make the transmission swap easier. Going to get a new rear driveshaft made after the swap anyway so all is good :)