Hi all,

so I drove my 2nd 928 GT today. This one had about 50,000 miles on it. The other had about 75,000 miles on it.

Point 1: What surprised me about the transmissions were that neither seemed very precise. The throws are big and heavy. It seems to me my 528e from the 80's was more accurate. Is this just my subjective opinion? Also the skill has to be there matching the rpm to the transmisson accurately. Otherwise the clunking is certainly there. OK, that's not really problem. Just practice. All in all, the transmissions remind me of heavy equipment. Is this because, big horsepower motors just need big transmissions? My SAAB 9-3 feels certainly more precise.

Point 2: one of the transmissions really did not like going into 1st gear when the car was moving at any kind of speed. Is this a synchronizer? Or, is it that the gear is bad from too many people test driving thinking that R is 1? Or, is it just typical for these transmissions? I only recalled this on one transmission, not both....

Thanks for your input, I have made a short list and will soon take the plunge with the best of my knowledge!

Cheers, JP

 

Point 2. I am a newbie to 928s, but when I was a 931 guy you NEVER put the car into 1st gear unless you were completely stopped. With almost every snailshell transmission the 1st gear dogteeth was prone to damage if you did this. I would venture to say other porsche transmissions had the same sensitivity. Of course, much more knowledgeable 928 guys will chime in any minute because they rock!!! But again, I wouldn't put it in 1st unless completely stopped.

 

Those later transmissions are usually quite stout synchro wise. How fast was the car going with the attempt at first? I can, with a warm trans, get the synchros to start properly winding up in 1st at about 15mph iirc. This is a 255k mile s3 trans

 

You can easily convert it to a short shifter. Makes a big difference.

With all the torque, as you alluded to, 2nd is fine for starting and stopping. Heck you can start this car in 5th.

 

No it has nothing to do with horsepower. My 997.1 GT3 had a very precise short throw feel to it, and it had 415hp. I started all this Porsche stuff in College with a 914. That tranny was like rowing a boat. I will never forget test driving a 69 911 and it shifted EXACLTY the same way. The saleslady stalled it like 3 times getting off the lot. Then gave it to me and remarked "Wow you have driven these before" But no I hadnt it was just the Trannies were similar.
This new to me 1982 928 I have is somewhere in the middle between that 69 911 and my GT3. So its probably just wear and those long throws.
You would NOT believe the GT3 tranny if you had driven one right after the 928 test drive.

 

The late model transmissions do have a long throw (same as the early), but you can tighten them up by making sure there's no play anywhere and fitting a shorter shifter. To get rid of a lot of play you can fit a new ball cup at the front, check/replace shifter bushes, and replace original oval bore bushes at the rear with delrin. You can get an even tighter notchy precise shift feel by converting to a different setup using the lizard shifter kit. I can drop my GTS easily into first on the move (and even easier by double de-clutching) ... but don't find too many situations where I need to do that with either early or late car ... second is usually plenty good enough. A normal late model gearbox will shift into first on the move, and so it sounds like the gearbox which was difficult to get into first has issues.

 

My 1990 GT goes in to 1st gear just fine when moving and its got 190k on the clock I have all the receipts and nothing for a transmission rebuild. The shifts are long and industrial like, I ordered a Lizard shifter kit from Roger, am excited to fit it next week. I have seen the video's and heard the feedback and it sounds like this will take it almost the other way with small and precise shift action. Thats the nice thing, its am old design car but so many people love it, there are so many ways to improve it incrementally.

Sounds like you should stay away from the GT with the 1st gear shift issue, or at least do some serious price negotiation.

 

I'm not sure whether Dave's "bushes at the rear" was referring to the rear shift coupling, but this is the very first thing you should check. This coupling joins the rod running back from the gearstick to the selector rod which protrudes from the front of the transmission, above the driveshaft. It is covered by a rubber boot. I think it is to the rear of the heat shield above the torque tube but, if it isn't, you'll need to remove the heat shield's screws and slide it forward.

What you need to check is whether the grub screw in the side of the coupling is tight. From memory, it requires a 4mm Allen key.

Remember that the synchro rings in a 928 transmission have to brake five feet of one-inch diameter steel driveshaft, so they do a lot more work than their counterparts in most transmissions. I always double declutch on downshifts to ease the load on the synchros. You should at least try to match the revs to the road speed on downshifts (though this won't speed up the driveshaft if you keep your foot on the clutch).

On upshifts, I do not lift off the accelerator pedal completely, to prevent the rpm dropping too low and making the car hesitate when you re-engage the clutch. Obviously, the opposite will occur if you keep the revs too high. This will help dispel the impression of heaviness relating to the shift. (It worked for a friend of mine some years ago, after he first drove a manual 928 and pronounced the transmission as having the worst shift he'd ever experienced!)

 

Another thing: change your transmission fluid and fill with a 75W-90 (as per the manual) synthetic. I ran 80W-90 for several years until I rebuilt my transmission and was told by my friendly 928 mechanic not to use anything other than 75W-90 synthetic or the shift would be heavy, especially when cold.

 

Glenn ... yes I was referring to the oval bore bushes in the rear shift coupler (can't understand why they deliberately put play there) and endorse your comments about the things to check in that area, including the grub screw. The rubber boot is also often torn and needs replacing. I think the rear drive shaft pinch bolt is another thing which doesn't get the attention it often needs (which can be replaced and torqued as a WYAIT when working on the gearshift coupling - manuals stretch those just like the autos).

I also think that technique has a lot to do with gear changing ease and speed .....
Gear shifting in any car can be accomplished without using the clutch, if you really have to, if you match the revs and have the 'feel' and timing to get it up or down a gear. Once you've learned that feel on an individual car, using the clutch just makes it faster and allows a little leeway on load and revs. Having that feel, to get smooth, almost seamless loading and unloading, minimises peak stresses on everything in the drive train, and means the synchros don't have to do much work.

I'm using 75W - 90 synthetic on both my gearboxes and it gives the best hot/cold shift performance.

 

Ok, so thanks for these inputs. I think I will avoid the car with the lower miles. We were only moving about 5 - 7 miles an hour. Wasn't sure the first time, if I had just pushed on the clutch incorrectly. But the second time, I knew... Personally, I LIKE the feeling of the transmissions in general, although I think the "precision feeling" could be maybe a little higher. You just get the feeling that you've got a real race car on your hands. :-))) And, yes, there is just a certain technique you have to have under control.

I have another drive in 2 weeks with a black one with about 60'000 miles. Looks like it will be between black and guards red. :-)

PS-in my SAAB 900 SPG classic I was always using Redline synthetic oil. Started at 50'000 miles and the transmission made it to 200'000 miles. That's not bad for a 900 transmission. (The transmission is clearly the weak link in that car...) It clearly gave me the best cold/hot performance.

 

This is a lot of it right here. You also want to make sure the input shaft bearing and clutch aren't dragging, but you need to time your shifts so the engine speed and gear speed match.

 

Dave,

I wouldn't say that there was noticeable play in my shift coupling when I rebuilt my transmission three years ago (and it was 28 years old then). When I read someone saying that the 928's shift is imprecise or sloppy, I think of the rear shift coupling being loose, or perhaps worn, first, then that the bushes at the base of the gearstick may be worn.

If you look in the workshop manual, one of the tools listed for rebuilding the transmission is a little gear lever which is fixed to the shifter rod, via that grub screw hole, to aid shifting gears by hand when the trans is out of the car. The reason for this is that the shift mechanism of the transmission itself is as tight as (insert your favourite analogy here) and heavy. If any lack of precision exists, it is somewhere in the linkage, not in the transmission.

I was taught to drive initially by a schoolfriend whose folks owned a wheat farm. I was given demonstrations of shifting crash gearboxes in an ancient Mercedes truck and a Ford tractor by a 13-year old. He later taught me to shift back to first without the clutch in my '59 Beetle paddock basher (which had no synchro on first gear). Years later, when a bracket broke and rendered my clutch inoperable in downtown Melbourne (fortunately at night), I was able to drive home, shifting without the clutch. I think my wife was even impressed. I've never been game to try this on the 928 though.

 

OT! This is that friend who taught me to drive: http://tinyurl.com/3dhkzjk

 

I think we're on the same page Glenn .... I think both late and early transmissions are good, although the early is a little less forgiving (more so if the double disc clutch isn't adjusted perfectly).

The issues with shifting seem to relate to the number of wear points on the linkage ... that no one checks them ... you get multiple slop points to varying degrees ... and then it's like stirring a bowl of porridge. I fixed my 82 (ball cup, shifter bushes, and rear coupler bushes) ... and the GTS had a loose grub screw. I'm about to put delrin bushes in the rear coupler because I just don't like the normal play in the standard bushes, even when new.

What a coincidence ..I've driven through Melbourne without a clutch too ... red lights were really interesting

P.S: Inspiring friend!