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Join Date: Dec 2007
Location: Rochester, MN
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1975 911s gear/clutch problem

Greetings,
I've owned my original 1975 911s since 1997. I rebuilt the engine and replaced the clutch in 1998 and it has about 12k miles on it since then. Over the years the car has occasionally popped out of gear. It first started happening when the car had been running for a few hours on a trip in 5th gear. Signs of it happening are when the tach starts bouncing wildly around and then a few seconds later the car would lurch, make a loud bang, and the engine would rev really high. I immediately push in the clutch and shift out of gear. Shifting back into gear then keeps the car going. It started happening about 15 years ago and did not happen very often. In the last 5 years, it started happening more often and in lower gears, until last year something changed where the gear locations seemed out of alignment. It is now at the point where I can't drive the car until I get this fixed. I'm open to suggestions on ways to fix this problem and also welcome recommendations for mid-70s 911 mechanics in the Midwest.

Thanks for reading.
Best Regards,
Derick
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-Derick
Rochester, MN
Old 05-15-2018, 12:32 PM
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Are you saying your clutch is slipping?
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Old 05-15-2018, 01:09 PM
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Popping out of gear can be lessened by renewing engine and transmission mounts, replacing all shift rod and lever bushings, and replacing the shift coupler bushings or upgrading the coupler. Two issues here: loose bushings in the coupler and shift rod can be preventing full engagement, and soft engine and transmission mounts can cause the drivetrain to move too much during driving.
Old 05-15-2018, 04:36 PM
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Quote:
Originally Posted by yelcab1 View Post
Are you saying your clutch is slipping?
*Edit*
*my original answer*
Yes but it is much more than that, see below.
*my new answer for this*
No, as the clutch does not slip when changing gears. What happens is the car pops out of gear without any activation of the clutch or shift lever.

Quote:
Originally Posted by RedCoupe View Post
Popping out of gear can be lessened by renewing engine and transmission mounts, replacing all shift rod and lever bushings, and replacing the shift coupler bushings or upgrading the coupler. Two issues here: loose bushings in the coupler and shift rod can be preventing full engagement, and soft engine and transmission mounts can cause the drivetrain to move too much during driving.
Thank you. These are great suggestions. My brother, dad, and I tackled a complete engine rebuild to put raceware studs in the engine block back in 1998. (updated oil covers, oil pump, and a host of other things as well) We also put a new clutch in at the time. After 20 years I'm not sure my brother and dad (both present and past mechanics) are up for another teardown. Finding a good mechanic for this vintage of 911 is difficult. There are a couple of dealers up in the Minneapolis St. Paul area but I'm not sure they will have a mechanic that has worked on this era of Porsche. I'll give them a call and find out. In the meantime, I'm still all ears for a midwestern mechanic that can tackle this.

Since photobucket went down pics of my car have gone missing from this site. Here are a couple to prove that I do actually own one The last one is a picture of a polaroid of me from in front of the engine in 1998.



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Rochester, MN

Last edited by dgbehrends; 10-11-2018 at 09:39 PM..
Old 05-16-2018, 08:30 AM
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Quote:
Originally Posted by RedCoupe View Post
Popping out of gear can be lessened by renewing engine and transmission mounts, replacing all shift rod and lever bushings, and replacing the shift coupler bushings or upgrading the coupler. Two issues here: loose bushings in the coupler and shift rod can be preventing full engagement, and soft engine and transmission mounts can cause the drivetrain to move too much during driving.
RedCoupe, I believe you were spot on with your assessment. I found a great Mechanic in Rochester, MN that agreed to investigate this problem. He replaced the shift coupler bushings and now 1st-4th gear including reverse all work great again. However, after the car was warm, I drove for about 10 minutes in 5th gear at about 3200 RPM going 65mph. I noticed the same old behavior where the tachometer would start to twitch and it felt like the car was going to slip out of gear as I felt the engine disengage a little. When that happens the tach bounces up and I immediately let off the gas pedal and push in the clutch. If I don't do this the tach will redline and the car will lurch. It's quite terrifying when it happens at highway speeds. I can't drive in 5th gear without constantly monitoring the tach for this behavior. My mechanic is going to take another look at the bushings and coupler and see if he can make any other adjustments for fifth gear. He said that if that doesn't fix it, there may be a problem with the manual transmission.
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Old 10-11-2018, 09:34 PM
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Awesome to see another clean '75S that someone put some time into. Rare to see any '75S that survived in that form, especially since the mid-90s were a low point. I wish my '75 looked that clean.
Old 10-12-2018, 06:35 AM
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