Hi all - Just got my 1970 small block motor and 4-speed manual transmission re-built. This past weekend we mated the two and put them back in the car. It was a long day...about 10 hours facing and over-coming several challenges getting it back in. However, we realized the next day that we forgot to change the main pilot bushing that goes into the back of the crankshaft (we did install a new clutch and everything). My question to you all...how serious of an omission is this? Would you invest another 4-8 hours to pull the motor and xmission back out, pull the two apart, pull the old bushing and install a new bushing...then put it all back together and back into the car?

I don't know that there was anything wrong with the bushing. When I had the xmission rebuilt, I don't believe they changed that main shaft (that would interface with the bushing) as I don't see it on the parts list. I would assume that if that bushing was bad, it would start to cause damage to the main xmission shaft, wouldn't it? And if that was so, the xmission re-builder would have said something and/or changed that shaft for me....correct? So, if I didn't have reason to believe it was bad to begin with...my xmission rebiulder didn't say anything about the main shaft...is it fair to assume that the existing bushing is ok and I shouldn't spend the time to re-do everything?

I don't know how old it is. I've had the car for 20 years and I have not replaced it. However, I don't drive the car much at all...couple hundred miles/yr. And I don't drive it that hard (although the previous owner did race it). My motor builder says that bushing really only sees load when the car is idling? If that's the case, I don't have the car idling that much (as I don't even drive it that much). Worst case I start to notice something in the xmission and I take it in and have it replaced for a few hundred $?? what are your thoughts? Is my risk low? What would you do if it was your car? Or am I risking significant damage that will bite me later?

I appreciate your input!

 

If there was nothing wrong with the bushing, and you are certain that it IS in there, then I wouldn't worry about it. Why would it take you 8 hours to pull a tranny & clutch to change the pilot bushing?

 

rebuilt. same crankshaft? are you sure? check with who did the engine if it is the same crank and did he leave it in place? and if he recalls seeing it and his opinion of the condition. how easy did trans mate to the engine. popping right in the last 3/4 inch with no fighting-finessing is a sign there is no bushing there. did you eyeball the clutch disk alignment? if so, you were using pilot bearing as reference and it is there. you would have to notice if you were checking clutch disk on center if there was a big open space and nothing to compare clutch teeth alignment to.

 

No need to pull the engine. Remove the trans and bellhousing and clutch.

 

Thanks for the comments guys. We are 99% sure it is there. The motor builder said he does not take that bushing out when he does his work...he assumes "the guy that's putting the clutch in will evaluate that" (which is me and I made the mistake). So, he confirmed he didn't pull it out...so it's there. I did not inspect the bushing at all, so can't say if it's good/bad. But I have no reason to think it's bad. I would think if it was really bad, there would be signs on the xmission shaft, and my xmission rebuilder didn't say anything about the shaft and didn't take the opportunity to charge me for a new one (I've now learned the mark-up on the parts for that...wow). The xmission took some work to get mated to the motor....it definitely didn't just slide in. In fact, we had to kind of pull it in the last bit with the bolts mounting the two halves together. So all signs are the old bushing is there....and odds are there is nothing major wrong with it.

Why would it take me 8 hours to pull the xmission? Same reason I didn't check/install this bushing! Ha! seriously, I'm just not as seasoned and am learning a lot. Plus, I don't have a lift...can you really pull the xmission without having a lift? Just jack stands?

Thanks again guys...sounding like I will just let it be.

 

I put my car on 4 ramps, lock down the brakes, and pull my tranny thataway. Many times. It's a lot easier now that I made the crossmember removable, but the first couple of times I removed the old M-21 by working around the crossmember.

 

it is not fun. finesse and a 120 lb tranny are kinda mutually exclusive. way better if you have the hoist there is to lift it off the mounts and go forward another couple inches. if you looked in thru the clutch splines as you tightened the clutch pressure plate you were sighting into the pilot bushing.

 

Leave it be. I would not bother.

 

Yes, you can remove the tranny while on jack stands and laying on cardboard, lol. I'm 65 and can do it in a couple hours by myself. Tranny weighs 75 lbs and it's easier to remove if the shifter mounting plate is removed, for my '76 anyway.

 

Run it now and worry about later it if the shifts are bad. Bad pilot bushing symptoms are a lot like poor free play adjustment or a heat warped clutch.

If all the adjustments are good and it is still hard to get into reverse then the disk is dragging. Then you might consider tearing it apart to replace the bushing and verify the clutch is right.

 

ya the bushing is seeing load when the clutch is disengaged (foot to the floor) and holds the clutch disc centered while its floating, so the load is just the weight of the clutch disc and load of the input shaft spinning. if you start to get a wobble feeling in the shifter or weird noises withthe clutch pedal in it could be a sign to change it. Run it until you have issues, you probably never will. Also if you feel a tanny vibration at high rpm it could be another sign, but again, most likely isnt ever going to be an issue

 

Thanks all - I'm going to leave it be and move on. I appreciate the comments as well as what to look for in the future as signs it might be going bad.

stay healthy!