After doing a few things here and there to the OB over the last few months, I decided to take her out for some spirited interstate driving. She performed like a champ until shifting from 4th to 5th. 85mph, approx 4000 RPM. When attempting to make the shift it made a sound as if I had not engaged the clutch. I immediately backed off and shifted back into 4th. I dropped down to about 2800 RPM and tried again. It was not happening. I was far away enough from the house that I thought it best just to slow down and head back.

FWIW, I have little to no mechanical experience. That being said I immediately started searching for DIY transmission threads. I have several saved resources that seem to have conflicting info.

Sychros?
the gear itself??
gears swapped in pairs?

The good news is I have a spare transmission.
The bad news is that it is still installed in a parts car AND I have no idea what I am doing.

The car is driven at residential speeds approx 8 miles a day, to and from work by my son.

Any ideas for a plan of action??

 

It's probably shift linkage that's not able to move all the way and nothing to do with the trans itself.

The plan of action is to look at the rear coupling, front ball cup and see where the lost movement is.

The rear coupling is held to the shaft by a 4mm hex keyed set screw. it has busings to wear and the front coupling is prone to all kinds of mischief.

 

I agree its most likely a linkage issue. Most Sychros that go are shifts made A LOT 1st to 2nd, 2nd to 3rd. 4th to 5th would be the least used shift in its life time.

Thank goodness for parts cars!

 

It could be linkage as the others have stated. But can you start the car push in the clutch and then put the car into first with no grinding?

 

Thanks Mike and Dean, Amen to the parts car.

I failed to mention that I have a short shifter AND when I was swapping out consoles I noticed the underlying metal had been cut. It looked as though a previous owner (at some point) made two cuts the natural width of the opening where the stick comes up (4 1/2" to 5" maybe) about 10" to 12" towards the dash. It was apparent that it had been lifted up. Kind of a make shift hatch, then pushed back done when finished. I bought a high end alternator heat sheild, trimmed it to overlap the affected area to cut down on cabin heat.

Can I use this "new" portal to access the linkage?

PS. I do have the WSM and access to PET and plan on researching it further, any additional help, advice or shared experience IS appreciated.

Thanks

 

Colin, yes. rev and first are fine. second and third are fine. Second is more of a straight up motion from first, instead of over and up but that is pretty typical with the short shifters I have previously owned. Fourth is as smooth as you could ask for. I might have tried to just cram it in fifth, regardless of sound, but I just didnt have it in me.

 

Update: I reviewed the info from the PO and found that he had replaced the front ball cup and had purchased the rear coupling but not yet installed it. So I have the parts....just need to get out there and figure it out.

We are picking up a 85 next weekend for a DD for my 19 yr old son. That will allow me to do more extensive service to the 79 since it can be parked for as long as needed.

 

I also vote for a linkage problem.......there are 3 items that wear and cause horrible shifting....not just the front cup & rear coupler but also the 4 little plastic bushings in the shifter itself...if those are worn or gone (don't ask) it makes things REALLY horrible........my current racer 1979 had a short shifter installed with only 2 bushings (requires 4) it was HORRIBLE...having loose front and rear couplers didn't help either.....it was like rowing a piece of steamed asparagus through marbles......nightmare

 

Since the PO did the really difficult front cup but not the more accesible rear coupler, I wonder if there was an attempt but the set screw is stuck and/or stripped.
The coupler has a 4mm key set screw that can be a problem. When you get to that point be careful and be prepared for some carefulness and patience.

 

Well, I am late to the party, but I concur with all of the above...coupler or ball cup popped up....

 

Here are pics I have of the whole assembly, shots of each section including a short shifter, a shot showing the adjustment points of the rear coupler,and a diagram of the rear coupler showing alternative delrin bushings you can put in. The rear coupler boot in the pics is torn and not complete.

 

Wow, thanks Dave for the pics. The new, un installed pcs are the two bushings. I have yet to pull the WSM to see if that is accessed from the tunnel or underneath.

On the bright side, I have befriended a local 928 owner who happens to have a three bay garage with a lift in each bay. I get his instrument panel working for him, swap out some tired interior rear QTR panels with some I have been refurbing and I should have weekend access to the lifts. While that might not be needed for this project I have a oil pan gasket and a tranny filter kit on the way. Time to get serious.

Thank you to all who have responded and bear with me as the updates might be slow, but they will be in real time as I make progress.

 

You get to the rear coupler from underneath. Before you take off the coupler you need to make sure that you understand how to get the alignment of it correct when you put the new one in. The two red arrows show what you have to loosen to remove the coupler, and they need to be tightend to give you correct fore and aft, and rotational position when you put the new one in. Those two points should be soaked with a penetrating oil before you attack them, particularly the grub screw, which can seize and become a PITA to get out. Take great care in loosening it, and make sure the hole is cleaned out so that the allen key goes in full depth.

With difficulty, you can just replace the bushings, without removing the coupler. I think Rob Edwards has done it.

The WSM has the procedure to set the whole assembly up to give correct alignment.

Access to a lift will make it way easier to do this job, and the other ones you have planned.

 

The custom cuts and access panel are proof that complete idiots have "worked " on the car before. Most likely the rear bushings are worn and need replacing then an adjust of the shifter location and you should be good to go .....

 

wow, another keeper thread for future reference (hope I won't need it)