Alright guys. Ive driven several old cars and trucks where the synchros were not really up to par with traditional downshifiting(i.e. push clutch in, shift gears, let clutch out slow and RPMs shoot up to match slowing down the vehicle).
Ive been seeing alot of posts how over time putting that kind of pressure on the turbo(to have to spool up much quicker than normal) and the synchros can result in excess stress on each one.
So if we were to depress the clutch, increase RPMs to rev match for the lower gear, then depress the clutch and engage. seems like it would help for smoother downshifitng.

seems like a lot of work, but its a thought. anyone drive like this?

 

I double clutch on the way down. It's easier on the synchros and the clutch if done right.

There's no way either method of downshifting will have any effect whatsoever on the turbo.

 

When I was still driving OTR, that's how we all did it...the only way to downshift was and still is having to match engine RPM to tranny speed. Some use their clutch, some don't. Personally, I used both depending on my mood and the terrain I was driving in.

 

I will double clutch downshift when the transmission is cold. Once warmed up it's slides very easily into lower gear, but I don't rush it.

MikeyB

 

great responses guys..

 

I try to match rpms for downshifts.

 

I somewhat match the RPMs on the way down but don't double-clutch - just blip the throttle good as I'm letting out the clutch to lessen the RPM difference. Of course, you may not want to follow that advice since I'm currently having to rebuild my transmission. (Input shaft bearing went out)

 

Can someone explain "double clutch"?

 

Sure. When downshifting, you push in the clutch, shift to neutral, blip the throttle, push in the clutch, shift to the lower gear, and release the clutch. What you are trying to do is bring the speed of the input shaft up to the speed it will be spinning in the lower gear.

On an unsychronized transmission, you have to do this to get it into gear. On a sychromesh trans (like everything made since the '70's) it's not necessary to make the shift, but it does reduce wear on the synchros since they don't have to bring the input shaft and countergear up to speed.

It's also a good idea to bring the engine speed up as you release the clutch pedal to complete the downshift. This keeps the wear on the clutch to a minimum, and prevents damage to the torsion springs in the clutch disk.

 

Thanks, and how far are you from Butler/New Castle?

 

I downshift without clutch unless I need to stop in a hurry. 1st and fifth are hard to get in, but the rest I have figured out.

 

The other end of the state. I'm in the Philly area.

 

I'm fully capable of driving without pressing the clutch pedal, but WHY would you do that to your synchros?

if I've got plenty of time, I double clutch downshift... if I've got less time, I single clutch throttle blip, if I've got even less time, I just clutch it w/ no throttle

 

My brother the "Expert Trucker" says it's better to shift without using the clutch at all. It's done by pulling the trans out of one gear then applying pressure on the stick and matching the engine speed until the synchros let it go into the other gear.

What d'yall think?

Edwin

 

It has been said that this method isn't hard on the synchros. Heck, I've done it in OTR trucks. Any prudent person would have to believe that it does contribute to some wear and tear. JMHO of course.