915 Tranny Opinions - Cold vs Warmed

[JohnTucker]

Still in the learning process.

My '84 915 tranny is really a challenge/hot-mess when it's cold...and as it has gotten colder this year...more and more. Really tough to get it into any gear upon start-up.

But...when it warms up, it's fantastic. Shifts as smooth as can be. No issues.

Just checking if this is normal or a significant concern? Any feedback is appreciated.

John

[roblav]

Gear oil viscosity?

[JohnTucker]

Don't know. New car to me. The gear oil was changed in June according to paperwork...but no details on the oil.

[Bill Douglas]

Not an answer but further to add to the puzzle.

My 915 was like magic compaired with what you guys go through. I could shift from third to first. Almost like a Toyota. Warm or cold gearbox or daytime temp' all shifts were easy.

Then... I did an oil change from Swepco to fresh swepco (SAE 90 or SAE 80-90 something like that) and it's an arse to shift unless it's hot. And it takes a while to get hot.

[dreichman]

I agree with both comments above. Try changing the oil. You may be surprised what a difference it can make.

[pmax]

You run the risk of offending the 915 gods with anything other than Swepco but Kendall hypoid and equivalents are reportedly just as good.

Regardless I treat every shift in my SC as if it might be the last, with apologies to those stuck behind me when the light turns green.

[Uwon]

To the OP, your oil may just be low so you might as well just change it to Swepco. You won’t regret it.
Johan

[Locker537]

I run Kendall in my 915 with a limited-slip differential. It's what the previous owner recommended.

Take your time and be very deliberate with the shifting. Ensure the clutch is fully depressed.

When cold, shifting into second takes me a little more force. Just slow the shift down.

Now, downshifting from fifth to fourth, well, I've "kissed" reverse a couple times. Just the lightest grind, but man do I feel bad.

[Mike Andrew]

Mine is also cold blooded. Running Kendall in a J Walker rebuild with about 15K on it. As noted above, just take your time until it warms up, then take a little less time once it is warm. Not a Borg or Muncie that you can speed shift.
May want to pull the fill plug and make certain it has enough oil. If not, drain and fill with lube of your choice. Plenty of threads here about brand, viscosity, et'c.

[Peter Zimmermann]

Cold shifting characteristics will definitely improve when you use Kendall 80w/90 Hypoid Dino gear oil. DO NOT USE SYNTHETIC (75w/90) gear oil. DO USE patience! If you change the oil yourself always loosen the fill plug BEFORE draining the old oil. Sometimes Mr. Muscle has worked on the car and severely over tightened the fill plug making it almost impossible to remove, which might make it necessary to drive to a shop that has heavy duty removal tools. Always use quality safety tools to support the car before going under it!!!

[JBSC]

Originally Posted by Locker537

I run Kendall in my 915 with a limited-slip differential. It's what the previous owner recommended.

Take your time and be very deliberate with the shifting. Ensure the clutch is fully depressed.

When cold, shifting into second takes me a little more force. Just slow the shift down.

Now, downshifting from fifth to fourth, well, I've "kissed" reverse a couple times. Just the lightest grind, but man do I feel bad.

Regarding your "kissing" reverse while downshifting from fifth to fourth, you should try installing fresh shifter bushings and adjusting your shift coupler. My 915 was behaving identically - I did the aforementioned last weekend and the difference is night and day. I still baby it when shifting from first to second, but the feel is much tighter and engagement is more positive.

A simple procedure too - only took ~$20 and two-ish hours of my Saturday morning to complete.

[Locker537]

Originally Posted by JBSC

Regarding your "kissing" reverse while downshifting from fifth to fourth, you should try installing fresh shifter bushings and adjusting your shift coupler. My 915 was behaving identically - I did the aforementioned last weekend and the difference is night and day. I still baby it when shifting from first to second, but the feel is much tighter and engagement is more positive.

A simple procedure too - only took ~$20 and two-ish hours of my Saturday morning to complete.

With the winter looming here in New England, I'll add it to my list of projects for the off-season.

I've been under the impression that the "kissing" is mostly technique. The shifter has a nice positive "elastic" movement away from fifth and reverse, and I've only "kissed" reverse when distracted or plain old tired.

[Speed metal]

The Swepco voodoo is real.

[JohnTucker]

This is really great guys. Many thanks. Seriously - many thanks.

[JSV798]

Originally Posted by Locker537

I run Kendall in my 915 with a limited-slip differential. It's what the previous owner recommended.


Now, downshifting from fifth to fourth, well, I've "kissed" reverse a couple times. Just the lightest grind, but man do I feel bad.

I had this problem; you need to lengthen the fore-aft movement slightly. Mark the position of the coupling with tape, then slacken the nut and pull GENTLY back on the gear lever. Move it no more than 1mm at the coupling. Tighten and test. Repeat as necessary.

[Locker537]

Originally Posted by JSV798

I had this problem; you need to lengthen the fore-aft movement slightly. Mark the position of the coupling with tape, then slacken the nut and pull GENTLY back on the gear lever. Move it no more than 1mm at the coupling. Tighten and test. Repeat as necessary.

Thanks! Bookmarked this thread and took some notes for when I do that project.

Given the advice, here's another question:

Shifting into second gear, regardless of whether it is an up shift from first, or a downshift from second, takes more force and patience than any other gear.

There's a much more noticeable "synchro engagement" and "clunk" into second. This is more pronounced on track, as it becomes more challenging to rev match and shift smoothly at speed.

Any thoughts?

[Walt Fricke]

Rev matching (blipping) doesn't help downshifting (jusr car control and less stress on parts). Double clutching does help doenshifting - if perfect on the matching, you could shift without the clutch.

Knicking reverse is embarassing, but other than a little more fuzz on the magnets in the plugs, doesn't hurt anything, really. No synchros there, no small engagement teeth to round.

When adjusting the shift coupler, have the shifter boot op so you can see the reverse lockout pawl - be sure it always clicks closed in 5th. If it occasionally hangs up, or you have consciously to shove it full forward into 5th, you need a small fore and aft adjustment.

[JohnTucker]

More good stuff. Another thanks. I'll change the gear oil just so I know what it is. Thanks!

[JohnTucker]

Someone recommended double-clutching the 915 full-time. I went out today and put about 40 miles on the car around town, double-clutching the entire time and it was FANTASTIC. Not a single shift issue. NONE. It takes a bit to figure out, but wow...what a difference. I also found out, via couple couple badly timed shifts, that I have a very healthy clutch disc. LOL. Win win.