915 advice needed
 

Hi

I've owned my 83sc for two years and have never been able to get 2nd gear shifting consistently. It never grinds, just occassional (1 in10) difficulty getting ito gear on the first attempt. The problem is present on up and down shifts. All other shifts into 2nd and other gears feel good. I've done all the basics (bushings, fluid, mounts, clutch travel check and multiple coupler adjustments).

I'm reluctant to take into a shop without knowing what to expect. The transmission (1st and 2nd gears) was rebuilt 30k miles ago. Is there anything obviously missing from the rebuild list that should normally have been addressed?

Any help and advice appreciated

John

http://forums.pelicanparts.com/uploa...1565971344.jpg

Mine is a fresh rebuild, and 2nd gear requires double clutching and slow operation to get into nicely. If accelerating with spirit a good swift confident shift will fine second nicely as well...

Generally the 915 is a transmission that just doesn't care what you want it to do. lol

John; your trans sounds normal.
1. Before shifting into 2nd, do you allow the revs in 1st gear to get up to 3500-4000? "Early" shifts made at lower revs can make your up-shift more difficult.
2. Do you always use what I call a "two-part" shift? In other words, do you always pull the lever out of 1st speed, through neutral, and then pause at the pressure point for 2nd gear before feeling that the gear is ready to accept the shift? This technique has saved countless dollars of trans repairs, as well as driver frustration, over the last 25+ years! As you practice this shift it can be done quickly enough so that a passenger might not even notice it. And sometimes it takes a little more time.

Does double clutching qualify as a two-part shift?

Is that 75w90 synthetic in the box ? All the experts have said that's too slippery for the 915 synchro's.

Good call Pmax. Definately will make the trans "notchy" and more difficult to shift. Johner, swap it out for some Kendall NS-MP 80w-90, then change it again in 500-1000 miles.

Thanks all for the advice and feedback, that's helpful.

I did change the fluid to Kendall 80w-90 about a thousand miles ago, but bought enough to do a second change so will give that a go.

I gemerally try to make the upshift at about 3000-4000, but will pay more attention to that.

I've read your advice on the 2 part shift and try to follow that. I probably need more practice. The 9 out of ten shifts that go well feel really nice and positive.

Thanks for the encouragement; I'll persevere with trying to improve my technique. I'll also try to get a go in another car with a sorted 915.

John

John; just remember, each 915 is different, and it might not be able to do what the driver wants it to do, or thinks what it should do. Cars fitted with a 915 control the show, and almost always will get out of sorts if asked to do something that it can't. Be patient with yours, and learn what it likes, or doesn't like.

Because the 915 is what it is, Sybil, add to it 35 years of wear on the internals, as in shift rods and the bores that they ride in, play around with it until you get it the best it is going to be, but generally not perfect. Of course shift rod bushings need to be tight. Third gear was balking on my track car. between sessions would make minor adjustments and measure and mark each adjustment. Eventually, bingo, no problem in third and all other gears were still shifting correctly. No science, just trying stuff. Bob

Changing oil that only has 1000mi on it is a waste of money and effort and will change nothing. Your problem isn’t your oil.

Is other people's experience that the shifting is very sensitive to the coupler adjustment? I followed the recommended procedure and it worked first time, although with the occasional resistance into 2nd. I've tried a couple of adjustments since then, mainly to fine tune fore aft position, but each time the resulting shift performance has been the same.

The 915 will never shift like a 2014 Honda Civic SI. I pause between shifts, match rev’s, shift from first to second at 4000 and double clutch down shifting and coming to a stop . Does it still balk once in a while? Of course! It’s a 915!!

John, when I do fore/aft coupler adjustment, I park the car with both doors open, in a space where I have a true vertical item (an uncovered wall stud, a doorway frame, etc.) visible. I then get down on my knees at the driver's side of the car, stick my head under the steering wheel, and with the shifter in neutral, line up the bottom few inches of the shift lever with the vertical item, visible through the passenger side door opening.

Always lightly touch the shifter and move it fore/aft to the pressure point of each gear (the shifter should stop at that point). Find the mid-point of that motion, set it there, and compare it (the bottom few inches) to your vertical item. That will give you your correct vertical adjustment, with no guess work.

Difficult 2nd Gear
 

John, based on your rebuild list it appears the shop replaced all synchro components associated with 1st and 2nd gears - nothing is missing from the list.

--------------------------

Since your trans has new 1-2 synchro components and the problem is intermittent / unusual, I tend to think the problem is external to the transmission - possibly something causing a temporary, slight misalignment between your shifter and trans.

Bushings immediately come to mind, but you mention you've addressed them.
- Is your shift rod bushing (in the tunnel) in like new condition and lubed. This one can be problematic if worn or sticky.
- Are the coupler bushings in like new condition?
- Shifter ball socket bushing condition?
- How's your engine & trans mounts?
If any of your bushings are questionable, replace them - they are cheap. Also you may consider upgrading your coupler with one like the Wevo PSJ, or Stomski.

The stock shifter is also a weak link with respect to consistent precision in my opinion - my Wevo provides exceptional alignment for 1-2 shifts, and I believe the Seine Gate Shift provides a similar feel & function at a more attractive price. The Wevo shifter also makes couple adjustment a no-brainer.

Bottom line - I rebuilt my trans and have Wevo stuff and all new bushings mentioned above, and it shifts as good as a 915 gets. When properly adjusted, I've never had problems getting into any gears.

--------------------------

Another thought associated with the transmission - but this one is just a theory of mine.

When I was rebuilding my trans, I spent a bunch of time playing with the synchro's on the bench and assembled on the shafts - observing how the components worked together when shifting.

Occasionally I noticed the synchro thrust block (AKA energizer) wouldn't release / remained wedged against the brake band - which made it impossible to get into gear no matter how hard you tried to force it. If I backed off of the shifting force against the shift sleeve, and lightly bumped the synchro assembly in the opposite direction - the thrust block would release and the shift sleeve would slip over the synchro ring as normal.

I imagine this would be unusual since the normal vibes and jarring of a transmission would be enough to release the energizer block - but thought it was possible that this could cause occasional balking on an otherwise nice shifting trans.

If that were the cause of the issue (or even possible...), I have no idea if or how it could be addressed, other than attempting the gear, backing off and re-trying...

Here's a video I made that may help picture what I'm describing:

<iframe width="640" height="480" src="https://www.youtube.com/embed/BbBxR8stYRE" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

B]--------------------------[/B]

Good luck, Gordo

Thanks everyone, that's good and useful information again.
I'll re-adjust shifter and make systematic adjustments to see if there is any change. All shifter bushings at shift rod, tunnel and coupler are new as are engine and transmission mounts.

I understand the 915 won't feel or work like a modern transmission (and don't really want it to as I like the overall feel of the 915), I just want to get it working the best it can.

John

Thanks for the advice! Every time I adjusted mine in the past it was a bit of a hit-and-miss process.

i've driven three 915 cars and they all feel similar going from 1st to 2nd. To me this is how I'd describe it:
You push in the clutch and move the lever down thru neutral and you feel some resistance as you approach 2nd. If you keep pressure on the lever, it eventually sinks in and you have a feeling via the lever that you have fully engaged the 2nd gear cogs. Once in a while the shift goes into 2nd with out that bit of resistance and feels almost like a proper manual trans should. but more often than not, you have that awkward wait for it to slide in.

YES! That's how mine feels at times, then others it goes into 2nd like a good trans should. lol I so hate the 915.

Cracks me up! A lot of guys say they do not want their 915 to feel like a modern transmission. They like the feel. Nope! I would be dancing in the street if it felt like a mustang gt five speed!! Where is actually went into all gears all the time!!! But then I could not tell my Wife that she should not drive it because it is hard to shift !!!

No, that's not how a correct 915 works.
I have zero issues going into 2nd gear, ever.

https://www.youtube.com/watch?v=AmOwHoJlK14

<iframe width="560" height="315" src="https://www.youtube.com/embed/AmOwHoJlK14" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>