Reece Pettersen
Well-known member
- May 6, 2021
- 274
- 313
Wait, you guys lift when you shift? 
Sequential Gearbox - Do You Clutch or Not?
- Thread starter Dockmaster
- Start date
SeanRitchie
Well-known member
- May 6, 2021
- 390
- 924
This might be a good time to see if Dave wants me to write up a detailed tech article for the home page.
I used to always tell people to use the clutch for shifting (a sequential) up until about 5 years ago when we started really digging into the Gen 3 shift mechanism design and having a more comprehensive understanding of setting up no-lift-shift, and really understanding what needs to happen to make them shift properly.
Now it is true that older Mendeola and current PBS shift mechanisms are not the best. These are well known to have issues shifting quickly enough on their own, with or without the clutch. This is what leads to dog wear.
I now feel that using the clutch for upshifts can actually cause more wear on the dogs compared to shifting with the clutch, as long as the foot-to-hand coordination is there (and not everyone has that).
I believe that using the clutch to upshift, when done too slowly, can cause the input shaft to slow down too much before the shift lever is pulled. This is when you let off the throttle pedal, push the clutch pedal down, then pull back on the shifter. This is typically no less than 1 second even for the fastest feet, more like 2-3 seconds. Keep in mind that the transmission shifts in less than half of a second once you push/pull on the shift lever.
Where as preloading the shift lever, then yanking back once the torque has released, will allow the dogs to pull out of the gear they are in and throw into the next gear much faster. When the shifter is preloaded, you are effectively loading the dogs against the gear they are in (the engine torque prevents the dogs from pulling out of gear due to an undercut in the dogs that hold them in gear), once the engine torque releases you can usually feel the shifter release, then make a full pull back to shift.
If the input shaft slows down too much, the dogs can "reverse thrust" on the decel side of the dog. I have had a few conversations with customers saying they could not pull on the shift lever if they were too slow to shift. The car will start to slow down enough that the weight of the car starts to push against the decel side of the dogs, effectively locking the fork into the gear it is still in.
Dog engagement gearboxes have to be shifted as fast as possible. You are not relying on a synchronizer to match the speed of the gears and allow it shift easy. You are quite literally slamming the gears (or dogs) into each other.
Something that helps to keep in mind is that when you are pulling/pushing on the shift lever, you are really only pulling the shift fork out of the gear it is in. Once the roller in the shift ratchet mechanism rolls over the top of the ramp, the spring takes over and quite literally throws the fork into the next gear, which you have no control over. A full push/pull on the shifter is really only half of the actuation.
I used to always tell people to use the clutch for shifting (a sequential) up until about 5 years ago when we started really digging into the Gen 3 shift mechanism design and having a more comprehensive understanding of setting up no-lift-shift, and really understanding what needs to happen to make them shift properly.
Now it is true that older Mendeola and current PBS shift mechanisms are not the best. These are well known to have issues shifting quickly enough on their own, with or without the clutch. This is what leads to dog wear.
I now feel that using the clutch for upshifts can actually cause more wear on the dogs compared to shifting with the clutch, as long as the foot-to-hand coordination is there (and not everyone has that).
I believe that using the clutch to upshift, when done too slowly, can cause the input shaft to slow down too much before the shift lever is pulled. This is when you let off the throttle pedal, push the clutch pedal down, then pull back on the shifter. This is typically no less than 1 second even for the fastest feet, more like 2-3 seconds. Keep in mind that the transmission shifts in less than half of a second once you push/pull on the shift lever.
Where as preloading the shift lever, then yanking back once the torque has released, will allow the dogs to pull out of the gear they are in and throw into the next gear much faster. When the shifter is preloaded, you are effectively loading the dogs against the gear they are in (the engine torque prevents the dogs from pulling out of gear due to an undercut in the dogs that hold them in gear), once the engine torque releases you can usually feel the shifter release, then make a full pull back to shift.
If the input shaft slows down too much, the dogs can "reverse thrust" on the decel side of the dog. I have had a few conversations with customers saying they could not pull on the shift lever if they were too slow to shift. The car will start to slow down enough that the weight of the car starts to push against the decel side of the dogs, effectively locking the fork into the gear it is still in.
Dog engagement gearboxes have to be shifted as fast as possible. You are not relying on a synchronizer to match the speed of the gears and allow it shift easy. You are quite literally slamming the gears (or dogs) into each other.
Something that helps to keep in mind is that when you are pulling/pushing on the shift lever, you are really only pulling the shift fork out of the gear it is in. Once the roller in the shift ratchet mechanism rolls over the top of the ramp, the spring takes over and quite literally throws the fork into the next gear, which you have no control over. A full push/pull on the shifter is really only half of the actuation.
lincster
Well-known member
- May 5, 2021
- 767
- 561
Sean, I have tried preloading my S4, similar to how I did my Fortin, and I can feel "something" in the shifter.
Or is your definition of preloading different?
IMO, preloading is where u are actually pulling back on the shifter and removing the "neutral" position of the shifter, if that makes sense?
Or is your definition of preloading different?
IMO, preloading is where u are actually pulling back on the shifter and removing the "neutral" position of the shifter, if that makes sense?
Rorschach
Well-known member
- May 6, 2021
- 822
- 770
Pushing the clutch pedal to shift a non-synchronized transmission is for nancy boys and dudes in truck driving school
Camacho
New member
- May 22, 2023
- 15
- 2
If the dogs are under a load you can pull back and hold it for the next shift .
Lift the throttle and the next shift will drop in .
Good for fast drag style shifting .
Reece Pettersen
Well-known member
- May 6, 2021
- 274
- 313
*This won't work with a no-lift shift mechanism.
Surf and Dune
Well-known member
- May 8, 2021
- 288
- 280
Never used the clutch while shifting my Albins dog change H pattern. At least in my case, that trans had to be shited so quick to be in the "sweet spot", that using the clutch slowed the process too much.
Funco4JM
Active member
- May 5, 2021
- 201
- 107
I have a Fortin FRS4 and I only use the clutch when starting/stopping and at times downshifting when I have to come to a quick stop and go down to 1st.
SeanRitchie
Well-known member
- May 6, 2021
- 390
- 924
What is "something"?
There needs to be as little slop in the cable/linkage as possible. If there is anything loose in the shifter, cable, rod ends, etc. you are going to feel that when you preload the shifter.
- Thread starter
- #30
Dockmaster
Well-known member
- May 5, 2021
- 963
- 779
What do you guys think of this video on how to shift a sequential? Not sure about his driving though. Donāt think I ever go back to 1st gear after Iām moving, Maybe his gear ratio is spread more than what Iām used to though?
SeanRitchie
Well-known member
- May 6, 2021
- 390
- 924
I don't know how this guy is but mostly good information with a few notes:
1. You can downshift without the clutch, it requires a blip of the throttle as you shift so throw the dogs forward and into the next gear. This is not easy when under braking at the same time. Using the clutch is fine, but if the shifter does not want to throw forward even with the clutch pushed in, give the throttle a little blip to throw those dogs out of the gear and unload the shift fork.
2. He says "You know when you need to pull the trans for service once it starts popping out of gear." I will have to buy this guy a beer if I ever meet him because he just helped make me some extra money.
The trans should be pulled for service if you start to see metallic slivers or excess shavings on the drain plug magnet. Slivers on the magnet are the corners of the dogs, once the corners of the dogs are worn off, it can pop out of gear. A sequential popping out of gear can cause 10x more damage to other parts as it can force the shift drum to rotate and shift into the next gear under load, which them tears the dogs off of that gear. This cascades through every gear until there is nothing left.
As I've already noted in this thread, if you have an older Mendeola or PBS sequential that has the old style shift mechanism, it may not matter how well you are shifting the trans. The older mechanisms are slower to rotate and will cause wear on the dogs with even the best drivers. Upgrade your old Mendeola or Weddle sequential shift housing to the new Gen 3 mechanism for the best operation and service life. (PBS cannot be upgraded)
1. You can downshift without the clutch, it requires a blip of the throttle as you shift so throw the dogs forward and into the next gear. This is not easy when under braking at the same time. Using the clutch is fine, but if the shifter does not want to throw forward even with the clutch pushed in, give the throttle a little blip to throw those dogs out of the gear and unload the shift fork.
2. He says "You know when you need to pull the trans for service once it starts popping out of gear." I will have to buy this guy a beer if I ever meet him because he just helped make me some extra money.
The trans should be pulled for service if you start to see metallic slivers or excess shavings on the drain plug magnet. Slivers on the magnet are the corners of the dogs, once the corners of the dogs are worn off, it can pop out of gear. A sequential popping out of gear can cause 10x more damage to other parts as it can force the shift drum to rotate and shift into the next gear under load, which them tears the dogs off of that gear. This cascades through every gear until there is nothing left.
As I've already noted in this thread, if you have an older Mendeola or PBS sequential that has the old style shift mechanism, it may not matter how well you are shifting the trans. The older mechanisms are slower to rotate and will cause wear on the dogs with even the best drivers. Upgrade your old Mendeola or Weddle sequential shift housing to the new Gen 3 mechanism for the best operation and service life. (PBS cannot be upgraded)
