Bad syncro or bent throttle linkage?

Wrecked944 · 04-30-2002, 07:51 PM

Okay, this one is pretty weird...a few weeks ago, the throttle on my 1980 SC began sticking. Nothing too dramatic, it just liked to hang out at around 2000 to 3000 rpms. Grab the pedal with the tip of my foot and I could easily pull it out of it's "sticky" point. So I got down on the floor and pulled the gas pedal back and forth and heard a distinct scraping sound under the floor between the seats. Voila ! I figured I had discovered a kink in the throttle linkage. Should be an easy fix on the next sunny Saturday. But then, on a short trip to the store, I was idling at 1000 rpms at a stop light. When the light turned green, I touched the gas pedal, let up on the clutch and "BANG!" - the car popped out of first gear and the idle surged to 3000 rpms. Very weird. So I did some experimenting and found that EVERY time it pops out of first gear it surges directly to 3000 rpms and stays there until I pull back on the gas pedal. Normally, I'd just shrug and say, "Oh well, 22 year old 915 tranny needs new syncros. Time for a rebuild." But what is the sticky throttle connection? Any theories?

Thanks,

dad911 · 04-30-2002, 08:01 PM

Throttle linkage attaches to transmission through belcrank on the driver's side of the transmission. Bad Trans/ engine mount, or something is loose, causing linkage to hang. Or clutch cable runs near throttle cable/belcrank, interfering with throttle operation.

Wrecked944 · 05-01-2002, 05:40 AM

Excellent !! Thanks very much ! I'll pull up the e-brake assembly and the rear access panel and see what is going on in there. Hopefully, I can avoid a tranny rebuild. Wish me luck...

Thanks,

Jim Sims · 05-01-2002, 07:00 AM

You may have several problems. The scraping you hear in the tunnel may be due to the throttle rod guide bushings (there are 3) being worn or gone; you may find pieces of them on the floor of the tunnel. See:http://www.pelicanparts.com/catalog/shopcart/911M/por_911M_pedals_main.htm

In addition, one of your throttle return springs on the engine may have broken or come loose. There are two springs: one on the console plate on the top of the engine shroud and one on the throttle body of the CIS system. See the same pedal section in the Pelican on-line catalog.

Finally the "popping out of first gear" is likely due to a combination of a worn 1st gear synchro ring and 1-2 gear operating sleeve. I suspect what is happening is when first gear pops out, the shift coupler in the rear of the tunnel moves enough to bump or shake the throttle rod to cause it to move to "it's lowest energy" position, the 2000-3000 rpm point.

The throttle rod is easy to fix although the front two of the three bushings are sometimes hard to reach. The popping out of gear means a transmission overhaul is needed. Jim

Wrecked944 · 05-01-2002, 11:32 AM

Wow, thanks for the info. It is a bit sobering. Given that most good porsche mechanics in New England are booked solid through the early summer, is there any chance that a novice could fix the synchro problem? Hmmm...even as I type the question, it seems unlikely. Heck, is it expensive to just drop the tranny and replace it with a fresh one? The poor thing is 22 years old. It probably needs a rest...

Thanks,

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by JanusCole
Wow, thanks for the info. It is a bit sobering. Given that most good porsche mechanics in New England are booked solid through the early summer, is there any chance that a novice could fix the synchro problem? Hmmm...even as I type the question, it seems unlikely. Heck, is it expensive to just drop the tranny and replace it with a fresh one? The poor thing is 22 years old. It probably needs a rest...

Thanks,

Keep your tranny Janus, just get it rebuilt. I'd do it but I'm pretty busy with my own projects. If you want to pull the motor and bring the transmission up to Nashua I could help you/show you how to do it. Too bad you missed my tranny rebuild session a few weeks ago.
-Chris

Wrecked944 · 05-01-2002, 07:28 PM

Yes, I am convinced. I made a bunch of calls and all of the pros are very busy with the Spring rush. And since I am currently happily unemployed, I have all of the time in the world. So here goes nothin'. Folks, I've never dropped an engine and have earned my title of "Wrench Klutz"...but this seems like a good time to learn by pulling out the motor, fix my five broken head studs, and replace the synchros on my tranny...is this a nutty idea? What will I need? Perhaps some sort of engine stand? Some way to lift the car off the ground? Some device to lower the engine? Any special tools or chemicals? Prozac, perhaps?

I've gotten great and patient advice from this BBS many times despite my ignorant questions. If you folks think it is doable, then I'll gladly take the leap.

Thanks,

Jim Sims · 05-01-2002, 07:44 PM

You can do it but you'll need some tools, a good floor jack, some manuals (start with our host's 101 projects), a shop press or big vise and a shop or garage to do the transmission work in. Typically parts for a 915 rebuild are at least $500 and usually more like $800. Last winter, Tbitz rebuilt a 915 and so did my son and I; we left some records in the archives. Do a search under 915. Good luck, Jim

Wrecked944 · 05-02-2002, 06:46 AM

Okay, I just ordered the "101 Projects Book"...I have a Haynes Manual, Bruce Anderson's book, Porter & Morgan's "Guide to Purchase and DIY Restoration"...I keep seeing references to "errors" on the Bentley manual so I haven't yet purchased one...should I?

And here is where I admit my complete lack of rebuild qualifications...

"You can do it but you'll need some tools...a good floor jack...a shop press or big vise...a shop or garage to do the transmission work in."

May I ask what a floor jack is? And what is a "shop press"? Yes, I am very ignorant about this but I have an unreasonable lack of fear...I have a very large and spacious basement workshop with multiple benches and good tools...will I need an engine stand? I see that Pelican sells a device for removing engines and trannies in one piece...that seems very appealing...

"Last winter, Tbitz rebuilt a 915 and so did my son and I; we left some records in the archives. Do a search under 915."

I will be certain to do a thorough search. Thanks for the info...

"Good luck"

Thanks very much. The luck will come in handy when I'm covered in grease and swearing (no worries, I've been there before)...

Jim Sims · 05-02-2002, 07:00 PM

To see what a floor jack looks like check the Pelican Tools Section/Shop Garage/ Magic-lift 2-1/2 ton.... A floor jack and tall jack stands are required to drop the 911 engine/transmission assembly out the bottom of the car. The appliance sold to go on top of the floor jack to correctly tilt the engine and transmission for easily removal/installation is a very useful rig. I've used a home made version of such a rig. A shop press is a hydraulic cylinder or jack mounted vertically in a frame so that the hydraulic force (tons of force) of the cylinder or jack may be used to press parts apart and together. A shop press can be bought from Harbor Freight (do google search for their web site) for a few hundred dollars or one can often find them in shops and garages where you may be able to pay them a few bucks to press your parts apart or together. An engine stand is a useful place to mount the engine if you're going to do work on it otherwise you can store it on a cheap furniture dolly (a very low padded platform on small casters) . Reading through 101 projects will answer a lot of your questions. Despite the errors (even the factory manuals have mistakes), a used Bentley is probably a worthwhile purchase - watch E-bay for one. Jim

Bobboloo · Bobboloo's Garage

The Haynes manual you already have is quite good. I've used them for numerous cars with success. I consult mine regularly on the 911. It's more in depth than Waynes 101. But 101 is a good starting point. I actually have both ver. of BA's book. A++. Ideally the factory manuals would be nice but they aren't cheap or necessary in my opinion. I just got a used set for $250 in good shape and I'm happy.

Just count on this taking a long time since you have a learning curve to deal with i.e. have another means of transportation. Be prepared for setbacks step back take a breath and enjoy.

Taking the motor and tranny out is quite easy. You'll get a kick out of it. Just have someone around to help you steady it when you lower or raise. I made a plate to go under the motor for jacking it up to put on the engine stand out of wood. I can send you a template if you want.

These guys forgot one of the most important tools to have in your garage....a radio.

Bobby

Wrecked944 · 05-04-2002, 08:58 AM

Thanks very much for the info and support. You really have no idea how helpful it is. As I've said many times, I've found nothing but patient support and good advice on this BBS - despite my sometimes inane questions...and I am feeling a little silly about not know what floor jacks and stands were...seems obvious now...what you don't see is that Chris Bennet of the "Messin' with 911's" gang has also helped with knowledgable emails and advice...I just got my "101 Projects" book and I have begun reading...I intend to read voraciously and plan extensively before touching a single bolt...

...and fear not...I have alternative transportation...I always keep a "spare porsche 944" around so I never need to go without the Porsche Driving Experience...

-Thanks again,

Jorgeman · Jorgeman's Garage

Janus--I'm predicting a completely successful job in your "drop, rebuild, replace" project! You sound like you have just the right amount of irreverence, spirit of adventure and reasonably bottomless wallet these jobs usually require! And as you say--you're blessed with this BB--as we all are--which practically insures against failure! Re: Bentley's book--there is about 99% more right than there is wrong with this tome--get your hands on one if you can.

Good Luck

george '86 Targa