Question about Synchro's / Shifting

[lr172]

I have just purchased an '88 911 and am working through the issues with it. I notice that my shift into second takes some time. When I shift from 1st to second, I apply soft pressure, but there is resistance. If I hold the pressure there, it evenually slips in after about 3 seconds with no complalining or grinding. Third gear is similar, but does go in a bit quicker (maybe 1 sec or so). 4th and 5th slide right in.

I have done some searching here and based upon that have tried double clutching and that seems to cut the time in half for it to slip into 2nd.

Is this a symptom of a worn synchro? I assume it is, based upon my research, but would like to hear from the experts on this. The car has 125K on it and the only record that I can find is the PO putting in Redline back at 60K. He used 1 qt. of regular Redline and 2 qts. of Redline for limited slip. However, there are no option codes indicating this car has an LSD.

It is possible the fluid was changed after this, but I cannot tell from the records. I will probably replace the fluid for peace of mind. Can this improve the symptoms I decribe? Also, the behavior doesn't seem to vary based upon fluid temp. The behavior is the same, for the most part, cold as it is warmed up.

Thanks for your assistance here.

[john walker's workshop]

try some regular 80/90 GL-5 gear oil for the helluvit. otherwise, it's probably a tired syncro.

[Talewinds]

Is there a difference in the 1-2 shift when the car is cold vs. when it's warm?

[lr172]

Originally Posted by Talewinds

Is there a difference in the 1-2 shift when the car is cold vs. when it's warm?

Pretty much the same regardless of temp.

[lr172]

Originally Posted by john walker's workshop

try some regular 80/90 GL-5 gear oil for the helluvit. otherwise, it's probably a tired syncro.

John, thanks for advise. By regular, do you mean like a Mobile 1 75/90 or did you mean a dino oil?

[john walker's workshop]

dino oil. kendall 80/90 GL-5 for instance. you don't really need synthetic in those transmissions and there have been various complaints about hard shifting, especially cold with synthetic, so it's worth a shot.

[175K911]

Dino

[911pcars]

You shouldn't have to double-clutch from 1st to 2nd. Engine speed and thus input shaft rpm decreases during upshifts. Thus, synchro speeds will normally match as you wait for the revs to drop.

Try a change to Swepco first. If this doesn't work, perhaps the synchros are past their service life (used up by the PO).

Whoops. Retraction. I just noticed you have a G-50. Use the recommended synthetics for this gearbox.

Sherwood

[wildcat077]

I have an 89 Coupe which i just replaced the gear oil with Quaker State 75W140 GL-5
full synthetic and it takes about 10 kms before the car shifts smoothly into gear,especially betweem 1-2 and 2-3.Seems like you have to shift in slow motion until it warms up.
Although after it has warmed up,the shifting is butter smooth !

[burgermeister]

I have almost exactly the same issues as you, except my 1-2 and 2-3 are more or less the same. It doesn't take too much force to shift quick, but I am rewarded with a clunk and odd notchiness in the shifter, which suggests to me that the tranny is not happy.

I have gotten used to double clutching upshifts as well as down shifts (eventually I might even get good at it). Without a double clutch, it seems to take around 2-3 seconds for the tranny to want to get into 2nd or 3rd when upshifting (assuming I'm shifting near redline; it's quicker if I shift at lower RPMs)

3-4 and 4-5 don't have the issue, but then I'm rarely at redline when doing those shifts, so the speed differential of the transmission shafts isn't as big.

[Eagledriver]

Make sure your clutch is completely disengageing. You should be able to shift into reverse without grinding after a few seconds with the clutch depressed. Clutch should engage well off the floor (maybe 1/3rd of the way up).

-Andy

[wildcat077]

Once the 75W140 is warmed up i have no problems shifting from 2nd to 3rd at 6500 rpm's
and 3rd to 4th either.
Personally i find it shifts smoother than when it had oem 80w90 oil...
My Steve Wong chip,MK and Fabspeed encourage me to shift at that rpm... oh well ... lol

For what it's worth,you might want to try another brand of oil,you never know it just might work better for your application.Everybody on this site has their favorite brand,i guess it comes down to whatever works for YOU

[Quicksilver]

The G50 cars have a hydraulic clutch. Make sure you are getting a full release. If you can get under the car there is a rubber plug on the driver's side of the bell housing where you should be able to view the release to see if you are getting movement from all of the clutch pedal stroke. It just might need bleeding which is kind of a pain.
The stock clutch should feel fairly easy all the way through it's release. These cars had a problem with lubrication of the clutch release arm that can cause it to bind which requires an upgrade and VERY SPECIFIC LUBRICATION. Most of these have already been upgraded.
But if your clutch is easy and consistent then that isn't an issue.

One last detail is that the 1st to 2nd gear rpm drop is the largest of the all of them so it is a slower shift. Don't rush it. If it won't go faster you don't want to cause more damage.

BTW +1 on dino oil. SWEPCO is the best of them.

[lr172]

Thanks for all of the comments and suggestions, I really appreciate it. You guys are great!

Given that I have no problems shifting into Reverse, 4th & 5th, I am pretty confident that my problem is not fluid or clutch related. Getting into first is downright miserable (5 seconds or more). I think one of the PO's abused the synchros and they are shot. Because all of these other gears go in like butter, I don't feel that it could be something across the board, like the clutch, fluid, linkage, etc. Also, the fact that 1st is worse than 2nd, which is worse than 3rd is very logical for synchro wear.

In my shift to second, the engine has been at idle for at least a second or so and this is quite frustrating. I have begun the investigation of rebuilding the trans and will replace at least the first and second synchro and possibly 3rd. I will post a new thread for a bit of guidance on this.

Thanks again for your assistance.

[burgermeister]

lr172, if you get in the habit of keeping your right foot on the gas pedal during shifts, you can modulate engine speed during shifts (both up and down) and keep the RPM's just where you need them. Just in case you decide to nurse the tranny for a few more years.

[s5uewf]

I'd just recommend you make sure you are using good synthetic on your G50, the level is OK, and the hydraulic clutch is bled. As mentioned, also makes sure the cross shaft upgrade has been done.

Rebuilding a G50 is expensive, much more so than a 915, so before assuming you need to do this, i'd check all the easy bases. Hate to have you spend money on removal/teardown if not needed.

My G50 always shifted slower between 1 and 2, and always got easier once warmed up - and I do not think it had synchro issues. It did have Swepco in it when I bought it and switching to Mobil 1 did help, but it was always a characteristic of that trans.

Sounds like you are not getting complete disengagement to me.

How does it feel shifting into reverse?

[kidrock]

Isn't Mobil 1 a synthetic???

I know this is off-topic a smidge, but many previous threads on this same subject have people strongly recommending Mobil 1 synthetic for the G50...now, I'm seeing a lot of suggestions for dino.

What gives?

[lr172]

Wellllll. I took John and others advise and swapped the trans fluid for some Valvoline (dino) 80W90 lube. NIGHT and DAY difference! People are no longer honking at me because I can't get me fancy looking car into first gear when the light turns green. My first gear problem is completely gone. It easily glides into first now while I roll to the light and have no problem getting into first when pressing the clutch and waiting a second or two while at a stop.

My first to second shift is MUCH improved. Still a second or two delay, but it appears that this is pretty typical from what I have read. I'm confident that a synchro change would improve it, but it is now quite liveable. I can get into second before the revs drop below 2500 or so now.

To answer the other questions, I can slip into reverse a second or two after pressing the clutch. It glides in just as smooth as going into fifth. I have all confidence that my clutch is not hanging up or dragging. The PO had the release adjusted way at the other end of the travel (on my list to move it back to the middle before it starts to slip on me while engaged).

I am a pretty good wrench (completely rebuilt, hot rodded and tuned a Chevy 496 - 600 HP by myself) and would have dropped the engine/tranny myself as wells rebuilt the G50 myself, so cost isn't the key issue here. However, it is a lot of work and I would hate to do it unnecessarily. I will probably rebuild the engine and trans when I get near 150K

Thanks again for the support and recommendations. I am new to Porsches and really appreciate the support offered by you guys and this forum.

On a side note, for the benefit of others that may find this, the fluid that came out was blue. Anybody know what that would have been?

Larry


EDIT: THought I would add for those asking about DINO vs. synthetic. I believe that my synchros are worn and I speculate that the thicker dino oil helps to create more friction between the synchro and the ring on the gear. It is friction between the synchro ring and the opposing ring locked to the gear that spools up the gear for a smooth engagement by the dogs. I would expect that when the synchros are new, the synthetic works quite nicely. However, when the synchors become worn (i.e. smooth), the thicker/stickier oil helps to create more friction between the rings that the slicker, synthetics can't provide. This concept is the same as why that thick gooey STP could be added to oil in the old days to help reduce oil buring in cars with worn rings.

[Flieger]

Porsche type synchro-mesh design needs more friction to properly synchronise and to balk a pre-mature engagement of the slider and dog teeth. This need for friction means that the 901, 911, 915 and other Porsche syncros need Sweepco or another high-quality lubricant with higher viscosity than normal. That usually means a non-synthetic oil.

BTW, Sweepco is blue. That is probably what was in there.

I have heard that the BW type syncros on the G50 do not need as much friction for their design to function and so can more easily use thinner synthetic oil.

[john walker's workshop]

a lot of the transmissions that come in for a rebuild have swepco in them. last ditch effort at improvement, or the root of the problem?