Hard "downshifting" when hot H55

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lcolon

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Oct 14, 2007
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Location
East Bay, SF, CA
I have a puzzling issue with my H55 that started rather recently. When the transmission is relatively cold it shifts up and down through all the gears fine. When it gets hot (ie after driving on the freeway in 5th) it does not want to down shift to lower gears. Sometimes the gears will grind. Lots of resistance in the shift gate.

Does this sound like the clutch is not disengaging completely? If I rev the motor some I can get it to go into gear. My truck does have an adjustable slave and I was thinking of adding a 1/4 turn or something to it. What is strange to me is why this would not happen all the time and just when hot.

Upshifting through the gears is always fine.

Thoughts? Replace the slave? New fluid? Shifter seat and cap? Other?

Looking for some troubleshooting guidance before I go start messing with a bunch of stuff that is not a likely culprit.
 
How new is the trans, what fluid, when was last change?

Setup the clutch adjustment per the FSM, once its setup correctly, that is it. If the slave and/or master aren't leaking and are pushing the clutch release arm (which they are since you can cycle all the gears) they are functioning as designed. They just push fluid, that is it.

Usually H55 is pretty notchy to start and takes time to break in. Trick is to drive it smooth and put the clutch all the way in and shift. It's taken about 5k for mine to break in with one fluid change around 1k. This trans isn't designed to be speedy or buttery smooth like a car or modern trans, but it does improve with time.
 
The trans fluid was changed not too long ago as I had Valley Hybrids pull the whole mess to reseal the transfer case. The transmission is getting close to 100k Mi on it so not a break-in issue. I am the one who got the transmission installed (since new) and it never had this issue before. Good point on the fluid level, I will check it.

When I say hard to pull into the gate when downshifting, it does not want to go at all. I presume the slave was setup correctly but will check the adjustment per fsm
 
The trans fluid was changed not too long ago as I had Valley Hybrids pull the whole mess to reseal the transfer case. The transmission is getting close to 100k Mi on it so not a break-in issue. I am the one who got the transmission installed (since new) and it never had this issue before. Good point on the fluid level, I will check it.

When I say hard to pull into the gate when downshifting, it does not want to go at all. I presume the slave was setup correctly but will check the adjustment per fsm

Oh so the issue started post-transfer reseal at Valley Hybrids? I'd go in and have them sort it, haha.
 
Oh so the issue started post-transfer reseal at Valley Hybrids? I'd go in and have them sort it, haha.


It has likely been a year since I had that work done so not really something they caused. I am kicking myself because my truck was just in there for a smog pump change and I did not ask them to look into it. Georg hooked me up and had the truck out in a day. 60miles from my house so not all that convenient to drop the vehicle off. If I have to, I can get the truck to them but it might be something I can sort out laying on my back under the rig...
 
Slave had quite a bit of play in it so I tightened up the adjustment. FSM calls for 4-5mm. Will report back if that took care of the issue or not.
 
Slave had quite a bit of play in it so I tightened up the adjustment. FSM calls for 4-5mm. Will report back if that took care of the issue or not.

Thank you for looking it up in the FSM and figuring that portion out yourself. So many on here need to learn that skill. Looking forward to hearing the difference (if any).
 
Unfortunately the issue is still present. I am going to pull the shifter out and check the rubber seat and the shifter cup. Frustrating for sure.
 
either the clutch isn't disengaging completely or the transmission input shaft pilot bearing is binding. Whats happening is the gears aren't being allowed to spin down... so they grind on a downshift. Theres still a bit of a connection with the flywheel.

Shifting might be easier when its cold because the oil has more friction when its cold.

Until you get it sorted out, learn how to double clutch- get the engine rpms at the correct revs before attempting to shift down. This a good technique to learn anyway. Once you master it, the clutch will last forever.

and as a worse case scenario--- the synchros in the trans could have worn down to the point where they aren't grabbing anymore.
 
My 3rd gear buzzes a bit every once in a while when the tranny is hot. It has done it since it was new. Double-clutching does prevent it but often I am lazy...
 
either the clutch isn't disengaging completely or the transmission input shaft pilot bearing is binding. Whats happening is the gears aren't being allowed to spin down... so they grind on a downshift. Theres still a bit of a connection with the flywheel.

Shifting might be easier when its cold because the oil has more friction when its cold.

Until you get it sorted out, learn how to double clutch- get the engine rpms at the correct revs before attempting to shift down. This a good technique to learn anyway. Once you master it, the clutch will last forever.

and as a worse case scenario--- the synchros in the trans could have worn down to the point where they aren't grabbing anymore.


Thank you OSS for the input. I checked the seat and the cup under the shifter lever and they look fine. I also checked again the slave play and it looks good to me post my adjustment. I will drive the truck some more and see. Not sure how I determine whether the clutch is fully disengaged. Pull the inspection plate and have a look while someone depresses the clutch when the truck is running?

I truly hope it is not a sticky pilot bearing.
 
Yeah it's easy to check by yourself.
Cut a 2x4 board to the length that will allow it to jamb the clutch pedal to the floor and wedge up against the drivers seat. Make sure it's secure and can't pop off.

Remove the clutch inspection cover under the truck.
Start the engine and depress the clutch to the floor with the board and then climb under the truck and look at the spinning flywheel. The clutch disc should not be spinning.

If the clutch disk can't slide freely on the input shaft splines (it's stuck) it won't release fully from the flywheel

image.jpeg
 
Last edited:
Yeah it's easy to check by yourself.
Cut a 2x4 board to the length that will allow it to jamb the clutch pedal to the floor and wedge up against the drivers seat. Make sure it's secure and can't pop off.

Remove the clutch inspection cover under the truck.
Start the engine and depress the clutch to the floor with the board and then climb under the truck and look at the spinning flywheel. The clutch disc should not be spinning.

If the clutch disk can't slide freely on the input shaft splines (it's stuck) it won't release fully from the flywheel

View attachment 2425966
Great thank you for that procedure!

I will try to do this over the weekend. At least it will tell me whether I have a issue with the stuck pilot or whether the master cylinder / slave are not working correctly.
 
I’ve sort of experienced the same problem. My H55 came brand new in a box,
went on a new clutch.
I tend to drive more slowly than most, but I also am old school and double clutch regularly.
I call it ‘single up, double down’. Most times I’m slowing and downshifting I’m double clutching.
 
Got the inspection done. The clutch definitely stops spinning after a few seconds once the pedal is depressed. I guess I am going to have to double clutch it for a while till I get this figured out. The transmission has close to 100k on it - seems too soon to need synchros but I will discuss with Valley Hybrids and see what they think.
 
Got the inspection done. The clutch definitely stops spinning after a few seconds once the pedal is depressed. I guess I am going to have to double clutch it for a while till I get this figured out. The transmission has close to 100k on it - seems too soon to need synchros but I will discuss with Valley Hybrids and see what they think.
Double clutching is fun. Makes me feel like Steve McQueen.
 
Some gear oils don't play nice with the H55F. Mobil-1 75W-90 is one of them. It's too slippery and the synchronizers can't get a grip - so gears grind when downshifting
 

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