Need help diagnosing strange sound

[DJTM]

Ah, the learning curve I faced just a few months ago.

As a general rule ,a semi truck uses a PULL type clutch that has twin friction discs and a clutch brake. A clutch brake is for transmissions that do NOT have synchronizers and gear shifts are made WITHOUT touching the clutch pedal.

My bus has a semi trans that I installed to replace the Allison at545. I do NOT KNOW what your bus should have, but from what I read they had 5 speeds that were synchronized. I ASSUME that a clutch for that application would NOT be a pull type, but rather a PUSH type like a car/light truck.

Either way, you need free travel which you get from the adjustment you have found. Just give that rod end about 5 full turns and test to see what your travel measures.

Yeah i have the Spicer es53-5a 5 speed. It's got synchronizers on gears 2-5.

 

[nikitis]

I don't understand it technically but I do understand it from a use stand point. Transmissions with synchros you do not need to double clutch as the point of the syncrhos is to bring it down to turning speed in the trans for you so it can shift without much wear. If it does not have synchros you should double clutch when shifting. The first clutch press slows it down similar to what a synchro does for you automatically, and the second clutch press is the actual shift into next gear, and your timing needs to be perfect to not slowly do damage over time to the transmission. No human is perfect and will always be slightly off on your double clutch and this is why manual transmissions are considered wear items.

Most truckers and large semi's do not have synchros. Usually only the smaller manual transmissions have synchros like in a Sport Camaro or European car. Semi's are required to double clutch, but when you speak to most truckers they will tell you they never actually double clutch and just single clutch and they are unknowingly wearing out their transmissions faster.

 

[Mr P]

nikitits, I am a human, and certainly not perfect. I will never double clutch any transmission. I will "float" my semi trans. I can, and have, floated gears in several different synchronized transmission. I was good enough on an old 4 speed to float them AND chirp gears on the upshift.

Correctly floating is no harder on the trans than clutching or double clutching. And a manual trans is NOT considered a "wear item" in my book. Only the clutch is.

 

[DJTM]

I don't understand it technically but I do understand it from a use stand point. Transmissions with synchros you do not need to double clutch as the point of the syncrhos is to bring it down to turning speed in the trans for you so it can shift without much wear. If it does not have synchros you should double clutch when shifting. The first clutch press slows it down similar to what a synchro does for you automatically, and the second clutch press is the actual shift into next gear, and your timing needs to be perfect to not slowly do damage over time to the transmission. No human is perfect and will always be slightly off on your double clutch and this is why manual transmissions are considered wear items.

Most truckers and large semi's do not have synchros. Usually only the smaller manual transmissions have synchros like in a Sport Camaro or European car. Semi's are required to double clutch, but when you speak to most truckers they will tell you they never actually double clutch and just single clutch and they are unknowingly wearing out their transmissions faster.

I actually double clutch even though I know I don't have to because I heard it eases the wear on the transmission.

 

[DJTM]

nikitits, I am a human, and certainly not perfect. I will never double clutch any transmission. I will "float" my semi trans. I can, and have, floated gears in several different synchronized transmission. I was good enough on an old 4 speed to float them AND chirp gears on the upshift.

Correctly floating is no harder on the trans than clutching or double clutching. And a manual trans is NOT considered a "wear item" in my book. Only the clutch is.

Wow... I wish I knew all the different techniques, I have much to learn. So thankful for y'all and this forum that's for dang sure!

 

[Mr P]

DJTM, I haven't covered speed shifting or power shifting yet! lol

Just remember the goal of a smooth shift is to "ease the wear on the trans" and the way to do that is to match the engine/clutch disc RPM with the next gear RPM. The more you can match those speeds with the "gas pedal" the easier it is on everything.

 

[DJTM]

DJTM, I haven't covered speed shifting or power shifting yet! lol

Just remember the goal of a smooth shift is to "ease the wear on the trans" and the way to do that is to match the engine/clutch disc RPM with the next gear RPM. The more you can match those speeds with the "gas pedal" the easier it is on everything.

Actually the one thing I've failed to do when double clutching is blip the throttle before the second clutch. I did it a few times in the beginning but I never drilled it in. But that blip is important right, in order to rev match?

 

[Mr P]

Uh, when downshifting the engine/clutch disc needs to speed up.

Upshifting the engine needs to slow down.

 

[ewo1]

DJTM, I haven't covered speed shifting or power shifting yet! lol

Oh remembering the old days...318 detroit-13 speed road ranger.... with no power steering....

 

[DJTM]

13 speed...jeeeez... how high do they go?

 

[DJTM]

After much trouble shooting and trial and error over these past few months I'm happy to report that it looks like my "hesitation" issue has been solved. Turns out it wasn't hesitation at all but my clutch was slipping. Clearly I don't have much experience with a manual so I didn't realize what was happening, plus the fact that I'd recently had work done on the clutch I wasn't thinking that it could actually be the problem. Well, it was and it wasn't.

First off thanks to everybody that helped me to narrow down my issue, I learned a lot from you guys. Turns out Mr. P was right about the clutch pedal free play. I had never even heard of any such thing until he brought it to my attention. I adjusted my clutch pedal free play from zero to 1 inch by adjusting the clutch pedal linkage underneath the truck and it's like my truck came roaring back to life!! I'm able to actually power my way up hills again!! I'm not sure how much friction material is left on my clutch but it's enough to power up hills in 3rd gear. I gotta fix my shift linkage before I can get 4th & 5th again, hopefully there will be enough friction material to power through those gears as well, but that's another story. Thanks again guys!

 

[Mr P]

That's "two birds with one stone" as they say.

Now, about that "shift linkage"....what's up with no 4 and 5??

 

[DJTM]

That's "two birds with one stone" as they say.

Now, about that "shift linkage"....what's up with no 4 and 5??

Another thing that they got wrong at the shop unfortunately. It was working when me and my pops left New York for Houston. Somewhere in Jersey it stopped and the shifter no longer even moves toward 4th & 5th. It wasn't a big deal at the time because my dad didn't want me to go past 45 mph anyway lol. But, I'm gonna take a look and see what I see...Hopefully it will also be an easy fix.

 

[Flying I 365]

Another thing that they got wrong at the shop unfortunately. It was working when me and my pops left New York for Houston. Somewhere in Jersey it stopped and the shifter no longer even moves toward 4th & 5th. It wasn't a big deal at the time because my dad didn't want me to go past 45 mph anyway lol. But, I'm gonna take a look and see what I see...Hopefully it will also be an easy fix.

Not much experience with manuals either but I have a pretty good idea on the internal workings.

Your inability to use 4th or 5th might be narrowed down to the mechanical linkage being damaged, or the shift forks for 4th and 5th might have gotten jammed.

 

[DJTM]

Not much experience with manuals either but I have a pretty good idea on the internal workings.

Your inability to use 4th or 5th might be narrowed down to the mechanical linkage being damaged, or the shift forks for 4th and 5th might have gotten jammed.

Oh ok. I still haven't checked yet but I'm hoping it's something I can fix at the shifter.