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1985 911 hard transmission questions


HGGuate

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Hello to all.

I am new to the forum. I have been checking out a well maintained 1985 911 as a weekend hobby car.

The looks and feels nice, no rust problems, nice interior, working sunroof, electric windows and other creature comforts. The engine seems fine, the brakes work wonderfully and the owner is ready to sell for a reasonable price in my book. Miles are about 55,000 with a clutch replacement about two years ago (about 2000 miles ago)

Test driving the car over the weekend, I drove in the city and out. Although I enjoyed the ride greatly, I felt the transmission was particularly hard to shift with heavy "clunks" when gears shifted in and out. First gear was hard to find in stop and go traffic, and shifting to higher gears required a bit of a tug on the gear shifter.

The car has a short shift option and I am not sure if the "heaviness" in shifting is normal for this model year cars or if I am getting what a classic car usually has in store for its driver. Current owner said the transmission was hard and would be in all cars of this generation but i dont have another point of reference.

Any opinions? If this sounds normal, please let me know if over time the pleasure of driving the classic beauty overpowers the effort of the hard shifting. If you dont think its normal, please let me know what i could be looking at in terms costs for adjusting or fixing the transmission.

thanks, HG

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Hello

pre 87 synchromesh are Porsche Style syncros wo where inventet in the late 40´s for race transmissions. (Used by Ferrari, Alfa, Daimler)

The synchromesh is fast but not able to handle high masses.

When new the late 915 trany had a definitive gear shift feeling and a slight slopines in the shift lever. The shift force required was middle to high yet Porsche was a Sportscar and operating them should add muscle.

When those cars age the shiftinge linkage gets worn out and adds indefinate feel and slopinnes and also the synchromesh "wears" down especialy the first and secound gear wich have to handle the most mass load and are used most often.

The thing is when the dog theet are grindung down the gear change needs hard force to engage the gear and hard force to disengage the gear. This is what i guess is what you descripe as "clunks".

A other reason for the clunks and hard shifting can be a missadjustet clutch and some cheap rebuild clutchs wheren´t machined to spec and would never work as the factory designed them. The design has to short travelway on the pressure platte so even if the clutch is adjustet to the max the unit will never freewheel...

So the thing is either the trany is worn and needs rebuild or the clutch is one from those not performing units and at least maybe just some adjustment in the clutch cable with new bearings and adjustet Omega Helper Spring might fix it good enough.

Now wear on the 915 transmission syncromesh is relatet to how the driver operates the trany. The Porsche syncromesh need a short and definite "throw" with gentle hand ( 2 finger operation) if you are to slow and soft or massive to hard the synchros will give up sooner.

A other issue is how the car was used in city driving most gearchange is done from 1-2-3 while highway driving ist mostly in the 2-3-4-5 section. Spiritet race events tend to need 2-3-4 exept Drag Racing an slalom on parking lots who tend to load 1-2-3.

the thing is in germany you can find old 911 who only had seen highway use and those cars have a much better trany feel then the low milage city hopper garage queens. SO Point is Milage doesnt´say anything about a car and many Porsche odometers got a "repair" to fix the numbers.. much better is doing a testdrive with the owner let him sit into the driver seat and see how he starts the cold car and if he don´t show off the perfomance on the next corner with a stone cold engine, also feel/see how he handles the clutch/gear and how smooth he is while normal driving yet how fast he changes the gear under hard acceleration.

As Race orientatet trany the 915 can be upshiftet within 0,1 secounds or even faster and without lifting to much from the throttle (shift under partial load) the synchromesh will be happy with it as both gears have the same speed.

The issue with the Porsche is the downshift with the other gear having different speed an hanging a heavy car behind that wheel (Mass). So the perfect driver blips the throttle on downshifts (or double cluthes) and if he drives soft he just waits a secound to reenage the clutch. A good driver will upshift and downshift so smoth you wouldn´t feel it or nick your head.

Now as an mechanic i can testdrive an car an compare it to many other cars i drove and when the clutch is worn down it is mostly also time to look into the trany, but if the clutch fails or was oiled up the clutch service time isn´t trany servicelife cycle.

While the trany is out for a new clutch a additional 30-45 minutes and some gasgets are enough to look inside the trany and check it or just renew the syncros from gear1-2 wich are mostly worn enough to do it. (Also renewing the guidingtube and the tranyseal on the mainshaft and shift rod are things done now when the trany is out, preventive maintenance).

The seals on the axle studs can be replaced in the car.

Well an other advise on the actuall shoping is contact the company who serviced the car the last times and ask them how much they would need to "fix" the shifting issue but don´t stomp direct to the point first try to find out if the company thinks the trany is good as is or had the owner allready told that something will need additional dollars in the next time.

I´m Porsche Mechanic and im Piggy on perfection an there is always enough to do keeping a 911 perfect but on the other side you have to tolerate that those cars wear down and some do it rapidly as the owners don´t care and others are pampered by the drivers (Not saying they drive slow they just "feel" with the car and adjust the operation to Porsche perfection).

And there is always a point where the wear gets to the point of high expense as things wear beyond simple repair.

So catching the right time to rebuild is important but many costumers think thats the "usuall" way from Car mechanics to engage additional money and thats where older mechanics tend to just shut the mouth and let them drive untill they come in for themself or the car breaks down. Those are te best "deals" for a mechanic you dont have to discuss about the issue, its fact and also rebuild costs are at the max and if the owner gives up you can shop a good car for a steal.....

A other interrim solution would be to adress the issue with the owner by a fresh gearchange and have done an oil analysis to the old oil. Reoiling with newer 75-90 from Mobile/Castrol/Redline/Motul,, can improve shifting and the oilanalysis will always show that the trany isn´t new however if brass shows up its time to have a a partial rebuild (forks wear down) and the particles will wander trough the Roller Bearings and wear those down bound usage wich will add another 500euro to the parts list..

Now on pricing in the US just google some from the reputatet Porsche Shops and mail them. Most shops tend to make full rebuilds not wasting time on parts to find out if they are worn, partial worn or worn out others doing racing can make partial overhauls leaving the worn parts in wich will work for another lifecycle to the next rebuild. A good trany shop had been the AASE in Anaheim (Orange/LA) but they are out of buisness since years wich is also my status on US Trips wink.gif

In Germany a rebuild from the syncro stones and brake bands without renewing any gears or any other expensive parts will run around 300-500€ but ther eis one problem the thoots from the syncros are pressed on the gears, there is a way to renew them but Porsche changed in 1981 to a special asymetrich thootform on 1st and secound wich are not aviable at the aftermarked and reneweing them needes someone with "inside" contacts to the Porsche Trany Division or to the Sport division.

Using the prevoius symetric thoot set will not work as intentet adds additional force on upshifting and waers down faster.

(OK Sorry for getting to deep into details....)

as you seem to dwell in Guatemala you either look for a local shop and have the US prcing as comparsion level or you ship the trany to a US shop. A local shop has benefits even if they are asking overprice in comparsion to the more competetive US marked.

Grüsse

Edited by IXXI
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  • 1 month later...

I agree. The 915 transmission takes a bit of work to shift. In the first 2 years of owning a '79 911SC - I thought there was something wrong with the transmission - until I considered how old this technology is. 1979 was a long time ago and I can't expect it to shift like a late model car.

So I tried something - add a bit of revs before shifting. Voila - the shifting is about as smooth as it can get in a modern car. I also read somewhere that a 915 doesn't like being told when it wants another gear - you have to feel it. Sure enough - when you can "feel" the tranny wanting another gear - it shifts like butter. It definitely helps to give it a bit of revs prior to the shift. Oh yeah, when you can time the revs and the shift - I guarantee a grin on the face because the sound, the feel and the acceleration will work hand in hand and make you realize it takes a bit of work to do this right. But get it right and whoa!

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  • 2 years later...

I also live in Guatemala and I beleive that finding the right shop with experience with the 915 is nearly impossible. Very few mechanics have had a chance to work repetedly on this transmission so experience is far between. Most problems shifting with a 915 can be solved externally. I have a close friend with very extensive mechanical experience and the correct mind set (doing things by the book and with the correct tools) and with no time constraits.

I just purchase a 1985 911 coupe with 49,000 miles and a new clutch, with similar transmission issues. We wanted to start from the basics, after 250 miles, checking the correct adjustment of the newly installed clutch, followed by replacing shifter bushings and performing the shift likage adjustment. We later installed a Seine Systems Gate Shift Kit and polyurethane engine and transmission mounts. All this in theory would isolate any problems, if any with the transmission. The change was dramatic. The Seine Kit takes away the guess work and makes drinving all that much more enjoyable.

Great shifting all the time, with the ocassional strained, down shifting to second. except when the gearbox is cold (16-18C). Syncros here get to speed when oil is cold and decided to do some research on transmission oils.

I replaced my gearbox oil to Motul 300 75W90 LS synthetic somewhat reluctantly as Motul rep promise a no charge replacement to a Motul 300 75W140 or 90 PA if not satisfied. Unfortunately their is no Swepco 201 or Redline here in Guatemala. Drove 200 miles shifting primarily between 3,4 and 5. Transmission works well but somewhat slower as syncros have a harder time slowing gears up. They need some friction for them to work properly and the Motul 300 has a good dose of friction additives. Too slippery as I suspected. Will keep you posted what results from changing to a 90 PA (Mineral) or a 300 75W140 synthetic.

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