Building muscles with my 915 shift

[Ignatzcatz]

I've got my 2.4 powered 356 up and running at last but the accompanying 915 gearbox is not the best in terms of gear shifting performance. OK, I know I'm trying to select cogs by utilising a 58 year old gear lever which was designed for a four speed but second gear on the 915 is a a real bitch to get into. I've got to haul that lever back plus when changing down 5th to 4th to 3rd I have to double de-clutch to get any semblance of ease in shifting. Sooner or later the box will have to come out mainly to fix an aging 5th gear synchromesh bearing which would seem to be well worn by the noisy whine it's making so is there any modification I can do to the selectors on the box to ease the shifting? In the meantime I am emailing Stromski in the States to see if he may have a shifter which firstly will fit a 356 central spine and secondly may ease my gear change problems. I did read somewhere that wood shavings and banana skins shoved into a gearbox does wonders but I'm not so sure about that.

[911hillclimber]

FWIW:
My fully rebuilt 915 does it too, not always but usually going from 3rd to 2nd at low speeds.
First check the clutch is free when pedal is pressed and not 'just about' free.
My 5th will whine if engaged at too low a road speed, ie 50 mph is just about when the whine starts. Any slower and it gets worse, faster and it is gone. Vibration in the box esp if the box has been rebuilt/disturbed from new.

All these boxes are getting old.

[Sam]

A well set up 915 in a 911 works perfectly with standard internals. I’d not worry about fiddling with the inside of the box until you’ve exhausted your options with the lever and linkage.

[rhd racer]

Sorry, thought I responded yesterday but it’s not here.

Might be stating the obvious, but surely the 356 4 speed shifter has to be eliminated as an issue first? Can you make an adaptor plate to sit between the 2 bolt tunnel (assuming the same as a beetle) and the 3bolt 915 shifter? Then at least with everything matched ( the straight tunnel linkage won’t cause issues unless slop in the coupling) you will at least see what you are dealing with before thinking about the box.

Also, make sure you have decent gearbox oil. That fancy blue stuff that people swear is amazing is rubbish in a 915 and will make things measurably worse…..

[jwhillracer]

A well set up 915 in a 911 works perfectly with standard internals. I’d not worry about fiddling with the inside of the box until you’ve exhausted your options with the lever and linkage.

+1!! There's absolutely nothing wrong with a well set up standard 915 gearbox, it will shift as fast as I can do it!

After one of my early runs at the weekend I was asked when I had installed a sequential box.............
The reasonably expert observer assumed that I had because I was able to change down 2 gears so quickly from 3rd to 1st before the tight LH Martini hairpin at Wiscombe Park.

JW

[911hillclimber]

Has your hillclimb box been rebuilt Jonathan?
My 2nd can be really notchy at times where into 1st from Neutral, 3rd to 4th not bad etc, but 3rd to 2nd can be difficult.
It would never have left the factory like it, so something is not right.
Mine's been rebuilt several years ago by one of the best.
Snake oil is not good, just some proper Castrol lube as per the manual.

[hot66]

3rd to 2nd on mine is the sweetest change

[jwhillracer]

Has your hillclimb box been rebuilt Jonathan?
My 2nd can be really notchy at times where into 1st from Neutral, 3rd to 4th not bad etc, but 3rd to 2nd can be difficult.
It would never have left the factory like it, so something is not right.
Mine's been rebuilt several years ago by one of the best.
Snake oil is not good, just some proper Castrol lube as per the manual.

My box has been rebuilt more often than Trigger’s broom!
It started life as an RS/RSR Airport spec box, and at different times has had new synchros, gears, final drives and casings, including the time that it left most of its oil, and half of the CWP teeth at your feet on the Loton Park start line, Graham!
Cheers
Jonathan

[911hillclimber]

And I was on that very startline holding the rear wheel chock, remember it well, SPLATT!

As ever, mine is the odd one out. Do everything to get it right and it is not.

[gav p]

Mine’s been rebuilt several times over the last 15 years for various reasons, most recently earlier this year by someone who knows them far better than most. It is still quite a heavy shift and does sometimes balk as described above - worst shift on mine is 5th to 4th. Not something i’m happy with, spoils the experience. However, its only done ~500 miles since and may need longer… Also thinking of changing to Castrol B373 which ive used in the past.

Anyone here have a Wevo shift gate within the gearbox?


Gavin
‘73E -> 2.7mfi

[911hillclimber]

I've asked that same question but with zero response. A few on Impact Bumpers have, some say it's great some say it's un-noticeable.
I'm do it in my race car 915.

[Ignatzcatz]

Following preliminary consultation with Stomski Racing, an initial start in improving gear selection and shifting performance on the 356 will be the fitment of one of their shift rod to gearbox couplings. I shall be speaking with Steven at Stomski tomorrow and my hope will be that he will be able to supply a complete shift lever although I may have to fabricate some form of adaptor which will mate their production 911 shifter with my 356 3 bolt base. With regard to recommended transmission oil for the 915 box, on good advise I am using Swepco oil, actually I have this product in my 911 as well and whilst I haven't been able to notice any vast difference in gearbox performance in the 911 I would be pleased to hear from any of you guys if you have used any star performer in the way of gearbox oil. I shall let you know what Stomski come up with in due course.

[911hillclimber]

Oil:
Just experience with my 911/915 over the years. Used it years ago for a year after several years using Castrol factory spec oil from Halfords.
I have to say I found it far worse than factory spec, weaker synchro action and just a lack of feel.
Drained it out hot to the very last drop and refilled with factory spec and it was instantly better.
It has been changed twice since for factory spec.

I have another 915 box in my hill climb car with LSD (Helix type, not plate) and that is good too on factory spec oil.

IMHO, use the factory spec. oil.

Bob Watson told me not to use the Swepco and he was right.
Mike Bainbridge told me not to use it too.
Both very respected specialists in Porsche boxes, though Bob is now no longer with us.

There is a danger of a lot of opinions on this subject like any oil question, so this is just my experience.

[Nine One One]

Plenty on Swepco here from old threads and 915 gearbox syncro’s

https://www.ddk-online.com/phpBB2/viewt ... co#p519290

[rhd racer]

Glad there is a solution (wasn’t aware that 356s use 3 bolts too)

I used Swepco in my 901 box and found it horrid. On the advice of Chris Flavell, I switched to Motul 75/90, and after several changes the Swepco finally was cleared and it vastly improved the shift. The crux of it is that it is too slippery for small Porsche gears (my 901 box used several 915 parts, so would expect the impact to be the same), and the shift behaved like there were no synchros at all. If you touch it, you will see what I mean!

I now use the Motul in my Boxster with LSD additive and the 964 and have never had any issues.