Bad pilot bushing problem fixed. Valuable tip inside.
Thread Starter
Joined: Mar 2006
Posts: 4,668
Likes: 5
From: Central Kentucky
Bad pilot bushing problem fixed. Valuable tip inside. Okay I had a growling sound coming from the tranny area when coasting with the clutch pedal pressed. The sound was accompanied by a vibration n the shifter and clutch pedal and sounded and felt horrible.
I found that when coasting with the clutch pedal pressed, the rear wheels were driving the tranny input shaft along with the clutch disk at speeds that cause vibration and resonance due to a worn out pilot bushing. After pulling the tranny, the worn pilot was very obvious to see.
The tranny input shaft had a tad of side to side slop from normal wear and could not be properly supported by a worn pilot bushing which resulted in the sound and resonance. I even pulled the from plate off of the tranny ad the input shaft bearing and the pocket bearings looked perfectly fine.
Now this is interesting.
I saw that one third of the pilot bushing was not worn at all as a result of never making contact with the stub on the end of the input shaft. When I installed the new pilot bushing, I decided to leave it sticking out of the crank hole by 1/4" as opposed to driving it in flush like I did previously. I figure now that the stub on the input shaft will now make greater contact with the pilot bushing. If this is the case, clearly the bushing will last longer. After driving the car, there are no ill effects as a result of the new pilot bushing installed the way I described above.
This new pilot bushing has completely resolved the problem I had with the coasting resonance and growling sound.
I found that when coasting with the clutch pedal pressed, the rear wheels were driving the tranny input shaft along with the clutch disk at speeds that cause vibration and resonance due to a worn out pilot bushing. After pulling the tranny, the worn pilot was very obvious to see.
The tranny input shaft had a tad of side to side slop from normal wear and could not be properly supported by a worn pilot bushing which resulted in the sound and resonance. I even pulled the from plate off of the tranny ad the input shaft bearing and the pocket bearings looked perfectly fine.
Now this is interesting.
I saw that one third of the pilot bushing was not worn at all as a result of never making contact with the stub on the end of the input shaft. When I installed the new pilot bushing, I decided to leave it sticking out of the crank hole by 1/4" as opposed to driving it in flush like I did previously. I figure now that the stub on the input shaft will now make greater contact with the pilot bushing. If this is the case, clearly the bushing will last longer. After driving the car, there are no ill effects as a result of the new pilot bushing installed the way I described above.
This new pilot bushing has completely resolved the problem I had with the coasting resonance and growling sound.
Thread Starter
Joined: Mar 2006
Posts: 4,668
Likes: 5
From: Central Kentucky
I saw the wear mark or in this case, lack of wear mark on the stub on the front of the input shaft. I also measured the lack of wear mark inside the worn out bushing where it never made any contact with the stub.
So clearly by leaving the bushing sticking out 1/4", all of the stub will see contact with the bushing, as opposed to only 2/3 before.
So clearly by leaving the bushing sticking out 1/4", all of the stub will see contact with the bushing, as opposed to only 2/3 before.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
wrd..
"typically" pilot bushing/bearing wear is due to worn input shaft bearings. i undrstand your theory of getting more pilot bearing surface on the input shaft...but I would think the "cause" of the old pilot wear was due to influence on it from movement in input shaft (bearings or bent shaft) than the depth you set the pilot.
certainly time will tell if your method solves the problem long term, good luck.
BTW, and completely off topic, I followed your thread a few years back regarding "high clamp" PP on LT1 = BS or not.
SPEC-1 refered me to that thread to show me WTF their PP load is. I went to a local clutch company who uses a different "tool" to measure pressure and showed them the one from the SPEC site. The machine shown in their pic is a rivet press according to the manufacturer name noted by SPEC....
this other clutch company, ClutchNet, showed me a step by step process they do to increase clamp load (which I assume any clutch company "could" do). Stock PP measured about 2350 PSI and with their modification they said typically 3200+. They invited me back down to see the increased load on theirs vs stock if i ordered one and would not charge me if the results were not what they claim.
I am not saying ClutchNet is any better than any other clutch at this point but seeing their modest shop and each piece of the disc is fabricated there....no "china" componets like many other clutches.
"typically" pilot bushing/bearing wear is due to worn input shaft bearings. i undrstand your theory of getting more pilot bearing surface on the input shaft...but I would think the "cause" of the old pilot wear was due to influence on it from movement in input shaft (bearings or bent shaft) than the depth you set the pilot.
certainly time will tell if your method solves the problem long term, good luck.
BTW, and completely off topic, I followed your thread a few years back regarding "high clamp" PP on LT1 = BS or not.
SPEC-1 refered me to that thread to show me WTF their PP load is. I went to a local clutch company who uses a different "tool" to measure pressure and showed them the one from the SPEC site. The machine shown in their pic is a rivet press according to the manufacturer name noted by SPEC....
this other clutch company, ClutchNet, showed me a step by step process they do to increase clamp load (which I assume any clutch company "could" do). Stock PP measured about 2350 PSI and with their modification they said typically 3200+. They invited me back down to see the increased load on theirs vs stock if i ordered one and would not charge me if the results were not what they claim.
I am not saying ClutchNet is any better than any other clutch at this point but seeing their modest shop and each piece of the disc is fabricated there....no "china" componets like many other clutches.
Thread Starter
Joined: Mar 2006
Posts: 4,668
Likes: 5
From: Central Kentucky
I inspected the input shaft bearing and the front main shaft beraring and there were no signs at all of wear.
There was a tad of side to side play but I detected no end play but in all fairness I did not perform the correct procedure for measuring endplay due to a lack of time. I am not saying your wrong. But There is no visual evidence of bearing wear.
I do know that the last time I had the tranny out to fix an exploded TOB, I lubed the pilot bushing with some marine lube that I dont normaly use. Every time preceeding this last incident, I have used brake caliper synthetic grease and never encountered a problem like this. I think the wrong grease could have also played a role here.
I will run what I got and monitor things and if the problem returns, it will be time to look at the tranny berarings more closely or the balance of the clutch disk. I am also going to try reducing the amount I clutch break especially the circumstances where the disk speed tends to get a high when the engine RPM is at idle.
There was a tad of side to side play but I detected no end play but in all fairness I did not perform the correct procedure for measuring endplay due to a lack of time. I am not saying your wrong. But There is no visual evidence of bearing wear.
I do know that the last time I had the tranny out to fix an exploded TOB, I lubed the pilot bushing with some marine lube that I dont normaly use. Every time preceeding this last incident, I have used brake caliper synthetic grease and never encountered a problem like this. I think the wrong grease could have also played a role here.
I will run what I got and monitor things and if the problem returns, it will be time to look at the tranny berarings more closely or the balance of the clutch disk. I am also going to try reducing the amount I clutch break especially the circumstances where the disk speed tends to get a high when the engine RPM is at idle.
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