Trans knock video. Not for the faint of heart!

[deezgunz]

Vehicle: 73 88 NAS Series III

Problem: Knocking sound coming from the main gearbox.

Trouble shooting actions to date: At first I thought it was a clutch issue. Clutch inspected and driven plate changed. Also replaced the rear seal. Why not?! Everything was removed! Inspected the engine, arms etc. when sump was removed. Everything appeared in order except for metal in the sump! No metal when transmission/ transfer case oil was drained. Everything cleaned, fluids changed and buttoned up and the knocking sound still present.

Diagnosis: Drive in the main gearbox had slight side to side movement (checked it when transmission was out while I was changing clutch plate). A bearing is shot somewhere in the transmission. My guess is in the front output shaft.

Video: When I was shooting the video I put my hand over the area of the front output/bell housing/main gearbox and it muffled the knocking sound. This leads me to believe that the problem is in the main gearbox.

View My Video


I plan to remove the trans and open it up. I figure I will run into a broken bearing or the like. This is the first time I've open up a transmission and am going into it blind.

I've read other posts on the forum that were helpful (Oh noooo...transmission and the rebuilt link in that post). The OP said that his rebuild cost 1k! I'd like to replace a bearing or two and drive on.

Should I consider a new transmission?

I also need to ID my transmission (I read people talking about an "A" or "D").

Any comments/suggestions on a fix. Any and all comments are appreciated! Thanks!

[SafeAirOne]

On your video, if I listen really closely, I think I can detect the tick you are referring to.





If it's a transmission problem, anything that makes this sort of noise should be able to be seen when you remove the shifter cover with the transmission in-situ.

Is the transmission and transfer case in neutral in the video? Just wondering what configuration it's in when it makes this noise.

[slowmo]

I agree with Mark. Thinking about what could be making that noise I tend to think something with a linkage or selector fork. Does moving the shift lever a bit change the noise? I would take off the cover CAREFULLY, because there are little ball bearings for used as detents (see part number 35). Did you notice any brass flakes in the transmission oil?

http://www.roversnorth.com/Land-Rover-Parts/54

If none of this pans out, I guess you'll have to pull it. I would change out all the bearings. I went off shore for the majority of the parts. The Series III is a different tranny than my Series IIA so I don't know about parts availability.

[cedryck]

My 2 P.
I had a knock coming from the transmission (i thought), knock got MUCH louder when driving, and under load, it ended up being the pilot bush (bronze) in the fly wheel, was very worn,.

[deezgunz]

Thanks for all the replies. I took the top cover off (carefully) and removed the forks and there was no apparent damage. I did snap a pic of the most forward gear (nearest the bulkhead) that can be viewed. (Granted, I don't know what I'm looking at).



There were no brass flakes and the forks were not obviously broken.



I ran the engine in neutral and changed gears with the clutch depressed and the bang was constant. I ran the engine with the top cover off and the noise was present and it appeared to be coming from the front output area. I am going to pull it and open it up. As far as the clutch bushing is concerned it appeared ok but I'll probably replace it anyway...

[SafeAirOne]

I ran the engine in neutral and changed gears with the clutch depressed and the bang was constant. I ran the engine with the top cover off and the noise was present and it appeared to be coming from the front output area. I am going to pull it and open it up. As far as the clutch bushing is concerned it appeared ok but I'll probably replace it anyway...

Front OUTPUT? So we're talking about the transfer case then? Make sure the red lever is either fully forward or fully rearward and that it's not partially in neutral, allowing the gears to just barely grind, though if the transmission is in neutral, the transfer case shouldn't be doing anything.

[slowmo]

I believe that pic is of the 3rd-4th synchro.

Does the clicking stop when the clutch is depressed? When the clutch is depressed, the tranny is getting no power and if the wheels aren't turning the tranny should be motionless as well. If the clicking continues it is coming from somewhere else. No? Am I missing something?

[deezgunz]

I removed the transmission today and dug into the transmission. There was a little play in the primary drive and when I spun it by hand there was a bit of clockwise/counter clockwise play and it sounded "clunky". I manipulated the synchros by hand and all of them engaged and there was no obvious broken teeth etc. Here is a pic of the gears:



Here is a pic of the bushing. There is some scoring but there is no obvious damage.



The problem that I'm having now is the removal of the bell housing. I removed all of the bolts, nuts and primary pinion cover per the green bible but I'm not sure about the "joint washer". In short, the bell housing is hung up somewhere and prohibiting removal. I have about an inch of separation but I am stumped on how to remove the housing. See pics:

[SafeAirOne]

Before you get too deep, what did the bronze bushing in the end of the engine crankshaft look like and what did it measure?

[slowmo]

Geez deez...you move fast.

In the pic inside the bell housing, it looks like the layshaft clamp and bolts (the lower shaft end) are still on? Can't really tell, but going from memory that has to come off? Putting it back together is fun if you have three arms.

[deezgunz]

I opened up the transmission and removed the layshaft and the gears that came off the shaft. The housing, gears, bearings etc. proved to be clean and healthy. See pics:






This points to the bronze shaft bushing (cedryck/safeairone)! I feel confident with this diagnosis as I had a similar issue with my 109. I tend to overcomplicate things and now that I'm retired I have too much time on my hands. I'm going to button up the trans with new seals and install a new bushing. I'll post an update when i'm done. Thanks to all!

[Bud]

Please run your engine with the tranny removed. I just skimmed through the thread, but I'm not positive the tranny is your problem - hopefully it is.

[deezgunz]

Bud, excellent suggestion to rule out (or in) a possible engine problem. Started fine with no knocking so I'm sticking with the worn bushing.

Please run your engine with the tranny removed. I just skimmed through the thread, but I'm not positive the tranny is your problem - hopefully it is.

[Apis Mellifera]

Something I discovered years ago: those holes perpendicular to the shift fork shafts, the ones for the detent balls and springs, I'd recommend replacing the top cover and drilling the holes back to round and slightly larger to make sure the balls and springs don't bind. This allows the balls to positively engage the grooves in the shafts and has cured mine from jumping out of gear.

[Les Parker]

Standing the trans on the brake drum (upright) with a wooden block supporting the rest of the trans. has worked for me to reassemble both Series IIa and Series III transmissions. Hope this helps.
How did it all pan out ?