Gear Shifting Weirdness

[EsGeht]

The trans is a '72 915. It needs an eventual rebuild, but it and I have a working relationship which has worked for years as long as I shift gently, carefully and patiently. I can rush the synchros if I'm not careful up-shifting, but the weirdness comes when angling or "cutting across" from 3rd to 2nd when downshifting. I'll get grinding if I'm not very deliberate in making the correct "H" pattern route. Of course, I don't mash it into gear regardless, I back off and try again, making a more careful "H" pattern. This happens with the clutch pedal fully depressed - i.e., without lifting my foot off the pedal; I get either a grind or a smooth change. My question is purely academic, but why would this happen with the clutch fully depressed and no change to it while attempting unsuccessfully and then re-attempting successfully? Is my linkage adjustment suspect? Is the 3-4 shift rod not being completely returned to neutral while I'm trying to engage the 1-2 shift rod? I know the appropriate response is rebuild that trans! but I'm still curious. Thanks

[gled49]

What shifter do you have? Early 72 style or the tower 73 type. Make sure your shift bushing are good. Ball cup bushing, ring bushing on the shift rod and the shift coupler bushings back under the rear cover. I would start there then report back. Gordon

[EsGeht]

Early 72 style and each of the mentioned bushings have been replaced within the last 6,000 miles. Sorry, should have mentioned that.

[304065]

If it grinds with the clutch pedal to the floor, that means the input shaft is still turning, making it impossible for the synchros to do their job of matching speeds between the input and output shaft so the dogs can engage. Adjust your clutch per the FWM. Also check to be sure all the clutch cable parts are OK, no buggered housing, trunnion, bushings etc.

Where does your shift lever rest, have you adjusted that per the FWM as well? If it's set too far to one side or the other that could be part of the problem.

Last question: what happens when you shift the box without the clutch, by matching revs, both up and down? Don't try it into first. That will be an indicator of the health of the internals-- people shifted for years without synchros and got along just fine.

[EsGeht]

After replacing the bushes in the shifter and installing a new after-market coupler I did my best to adjust the shifter according to the factory manual, and it's been fine for the most part for several years.Each Spring when the car comes out of hibernation the trans seems very balky and these symptoms are more pronounced. This Spring it was terrible, so I did re-adjust the clutch, and that helped a great deal. From what you are saying it sounds like the clutch is still out of adjustment if the input shaft is still moving. Shifting without the clutch (and not grinding gears!) is possible, I'm just not practiced at it. Thanks, I'll have another go at adjusting the clutch.

[37yrold911]

the cable stretches over time (it stretches a lot right before it fails...) & the pivot hole in the pedal mechanism wear until it is out of round, so check those

how old is your gear oil?

[EsGeht]

Gear oil is Swepco 201 and no more than 4-5 years and 6,000 miles old. Cable may be quite old...hadn't thought of that. Thanks

[37yrold911]

I like to replace the clutch cable every 30 years even if doesn't look bad... :]

[EsGeht]

I had to check my records. Clutch cable replaced in 2003. Tightened it a couple of turns and the difference is noticeable. There is a full inch of thread showing beyond the locknut (type used on valve covers)- the clutch itself is at least 40,000 miles old, but it has never shown any sign of slippage and I'm pretty easy on it. I suspect the locknut has backed off a bit with use. I put another on to lock it down. As I say, just a turn or two has made a big difference. Thank y'all for the tips!

[37yrold911]

did you check the pedal cluster?

don't let the wear strand you in the outback someday