Winter Driving?

[FR Sports]

I find that sometimes it's difficult to get into 2nd even if I double clutch. Grinded my synchros a few times with clutch fully depressed.

[Suberman]

Originally Posted by daiheadjai

Yeah, that was one of the first things I noticed in the FWD to RWD transition... Handbrake shenanigans don't happen the same way...

My old SAAB 99 had the handbrake operate on the front wheels. Couldn't do handbrake turns but the handbrake made a nifty LSD long before manufacturers used the ABS system to do the same!

[J-Cam]

Originally Posted by FR Sports

I find that sometimes it's difficult to get into 2nd even if I double clutch. Grinded my synchros a few times with clutch fully depressed.

Try adding some engine rpm on your double clutch- You can raise the second gear shaft speed with engine rpm but you will have to be very fast and precise to catch the dogs when you shift out of neutral in cold oil. It takes practice and a little extra engine rpm but double clutching will work on a cold second gear.

If shift through neutral with really cold thick oil the shaft spools down very quickly, so you may now be asking the second gear sincro to spool the shaft back up on the upshift, against the drag of the thick oil.

With the exception of first, second requires the highest shaft speed (relative to the output) and is therefore is the most difficult. The close ratio between first and second adds to the problem by giving you less time for the shift before the second gear shaft spools below the dogs.

You could also just skip second and go to third when it's cold - third is easier because it requires slower shaft speed and more time for the shift (sincro needs only to slow the shaft).

[Suberman]

Only on a downshift, I think the poster is referring to the upshift. Double clutching is never done going up the gearbox. It can't work. Only downshifting.

A common solution to cold shifting difficulties is to mix a but of automatic transmission oil into the standard gearbox oil. However, only do this if Toyota/ Subaru approve. Be aware that this can cause shifting problems when the gearbox is warmed up. In line transmissions like our BRZ require different lubricants than fwd transverse gearboxes.

[wparsons]

Originally Posted by Suberman

Only on a downshift, I think the poster is referring to the upshift. Double clutching is never done going up the gearbox. It can't work. Only downshifting.

It can work if you're shifting REALLY slow and need to get the input shaft spinning again, but I can't see that coming into play very often at all.

[jonboy99]

Originally Posted by FR Sports

I find that sometimes it's difficult to get into 2nd even if I double clutch. Grinded my synchros a few times with clutch fully depressed.

Ground bro, ground. Although grinnded should be a word*.



*yes, i'm pissed.

[Suberman]

Originally Posted by wparsons

It can work if you're shifting REALLY slow and need to get the input shaft spinning again, but I can't see that coming into play very often at all.

Nope, you never need to help the synchros slow down the dogs. Any extra throttle just wears the synchros for no reason.

You have to remember these constant mesh gearboxes are never out of gear in that sense. All the gears spin all of the time. The reason double clutching downshifts works is the synchros have to speed up a lot of mass to get the dog speeds matching for the lower gear. Going up the box the gear cluster is naturally slowing down as you shift. There's nothing you can do to assist this slowing down.

Now if you're talking about double clutching an "upshift" because you've been coasting (naughty naughty) then I agree it can help but I've never met a gearbox I needed to double clutch a shift after coasting.

[Gords_zenith]

Originally Posted by Suberman

Nope, you never need to help the synchros slow down the dogs. Any extra throttle just wears the synchros for no reason.

You have to remember these constant mesh gearboxes are never out of gear in that sense. All the gears spin all of the time. The reason double clutching downshifts works is the synchros have to speed up a lot of mass to get the dog speeds matching for the lower gear. Going up the box the gear cluster is naturally slowing down as you shift. There's nothing you can do to assist this slowing down.

Now if you're talking about double clutching an "upshift" because you've been coasting (naughty naughty) then I agree it can help but I've never met a gearbox I needed to double clutch a shift after coasting.

I double clutch and throttle for an upshift when the trans is cold because I hate that dreaded "crunch" sound. So yes it can be done!
As some one else pointed out that the gear ratios are too close and with cold oil the input shaft simply comes a halt quicker with the clutch in. So double clutching and adding throttle for 2nd isn't a bad idea at all. Skipping gears can also be bad i.e 1-3 if it's not explicitly designed for it (corvette 1-4 skip shift for fuel mileage).

[Suberman]

Skip shifting a synchronized box is fine. Sequential shifting of street gearboxes is an unnecessarily controversial topic.

Double clutching an upshift is unnecessary, always.

The "crunch" you are concerned about is just the meshing of the shift dogs, they are designed to absorb that.

A firm shift with proper motion of the selector is all that is required. On a cold gearbox, shift deliberately out of first and then as a separate motion shift deliberately and firmly into second. Time these movements close enough together and the coldest shift will be smooth enough.

This gearbox improves significantly as mileage accumulates which, for triple cone synchronizers is not a surprise. This feels like a very robust gearbox for this level of torque. Probably can handle significantly more torque with ease.

[jonboy99]

Originally Posted by FR Sports

Has anyone experienced difficulty engaging 2nd gear when it's really cold? Does changing the transmission oil help?

Yep, there is a lot of info about this on the forum. Here is the main thread:
http://www.ft86club.com/forums/showt...+oil+aisin+bmw

When I first got my brz I really didn't like the notchy shift, and lock out of 2nd when cold - especially as my first km or so of commute has lots of stop signs. I put in the bmw oil at around 600km and although much better I found it would often crunch into 2nd (mildly) even though it would rarely lock me out. When warm it had just a suggestion of crunch too, which I really didn't like (wondered whether the new oil was too thin). I bought some motul gear 300 to try, but haven't got around to changing it yet, and found that over the last 500km or so the change is much better anyway even despite the cold temp.
I'm now left wondering whether the 'box just needed time to wear in and would be a lot better even with the standard oil (am now at about 3500km). So for now i'm going to stick with the bmw oil and see.

Make of that what you will!

Jon

[wparsons]

Originally Posted by Suberman

Nope, you never need to help the synchros slow down the dogs. Any extra throttle just wears the synchros for no reason.

You have to remember these constant mesh gearboxes are never out of gear in that sense. All the gears spin all of the time. The reason double clutching downshifts works is the synchros have to speed up a lot of mass to get the dog speeds matching for the lower gear. Going up the box the gear cluster is naturally slowing down as you shift. There's nothing you can do to assist this slowing down.

Now if you're talking about double clutching an "upshift" because you've been coasting (naughty naughty) then I agree it can help but I've never met a gearbox I needed to double clutch a shift after coasting.

No, no, no. Read what I said. When the gearbox oil is really cold if you're shifting slow the input shaft will slow down faster (or fully stop) than the shift so double clutching can actually help. When it's really cold it doesn't take much time at all for the input shaft to stop spinning with the clutch in.

You're not slowing down the input shaft, you're speeding it back up after it slowed down too fast during the first part of the shift.

Like I said originally, it's not something you would need to do often, but in certain situations it can be handy.

[FR Sports]

I tried double clutch with throttle already upshifting and still had difficulty going into 2nd. I guess it cannot be helped as the outside temperature the past few weeks was like -30C with wind chill. I'll try skipping 2nd or starting in 2nd the next time to see if it helps. Thanks for the suggestions.

[Gords_zenith]

Originally Posted by Suberman

Skip shifting a synchronized box is fine. Sequential shifting of street gearboxes is an unnecessarily controversial topic.

Double clutching an upshift is unnecessary, always.

The "crunch" you are concerned about is just the meshing of the shift dogs, they are designed to absorb that.

A firm shift with proper motion of the selector is all that is required. On a cold gearbox, shift deliberately out of first and then as a separate motion shift deliberately and firmly into second. Time these movements close enough together and the coldest shift will be smooth enough.

This gearbox improves significantly as mileage accumulates which, for triple cone synchronizers is not a surprise. This feels like a very robust gearbox for this level of torque. Probably can handle significantly more torque with ease.

Skip shifting is not fine! It causes undo wear on the syncros as they have to work harder to mesh the dogs, however it's not impossible.

I have 40K on my box and it's not any better and I've also had the fluid changed. Double clutching on Upshifting will not hurt anything. I've been driving manual for 15 years with several vehicles that were/are manual, I think I know what I'm doing but thanks.

[Suberman]

Originally Posted by Gords_zenith

Skip shifting is not fine! It causes undo wear on the syncros as they have to work harder to mesh the dogs, however it's not impossible.

I have 40K on my box and it's not any better and I've also had the fluid changed. Double clutching on Upshifting will not hurt anything. I've been driving manual for 15 years with several vehicles that were/are manual, I think I know what I'm doing but thanks.

Old fashioned thinking.

Sequential shifting wears out synchronizers.

Double clutching wears out master cylinders and release bearings. Done incorrectly, say while upshifting or incorrectly during downshifting, double clutching also wears out synchronizers.

I've been driving cars with manual transmissions for over 40 years, including some with worn out boxes and Alfa Romeos which require double clutching.

I'm pretty sure you don't know what you're doing and the fact that the shift quality on your car still hadn't improved may be the result.

Talk to me again when you've put 100,000 miles on the same manual transmission, and more than once.