PDA

View Full Version : Shifting Problem



dthompson
09-13-2015, 08:28 AM
Hoping to get some help diagnosing a shifting problem...

Background: Recently rebuilt the transmission replacing all the blockers with CF lined ones, replaced mid-plate and added a 0.005" shim to the input shaft (it was over the .002 to .006" tolerance listed in service manual). I also replaced the slave cylinder and the hydraulic line. I have bleed the clutch several times, the most recent time using a pressure bleeder connected to the nipple of the clutch master cylinder. Used acdelco synchromesh with a bottle of motorcraft friction modifier.

The problem: sometimes it seems that it is hard to get it to go into first gear. like it is being blocked. other times it is fine. Ive had issues shifting it higher in the rpm range, like 5000rpms, and it has ground going into second. other times it felt like it was being blocked shifting into second and third at high rpm.

The test: Please see the video... You will see that the wheel moves slightly when i put it in first gear sometimes.


https://www.youtube.com/watch?v=UekMPFDA8RI&feature=youtu.be

My hypothesis: I don't have a lot of experience diagnosing stuff like this. It would seem to me that since the wheel moves some when going into gear, that the input shaft has to be spinning during the shift. if the input shaft is spinning then the clutch has to be at least partially engaged. Since the wheel stops spinning after the shift has been made, the input shaft is no longer spinning. I would suspect that the clutch disk is sticking on the input shaft and not sliding properly. If the clutch slave is bad, i would expect the input shaft (and wheel) continue spinning with clutch in and the transmission fully in gear. The input shaft was cleaned with brake cleaner when I installed it, but I did not put any lubrication to it.

Can anyone with some experience offer some insight on this issue?

Thanks,
Derek

davec73
09-13-2015, 10:26 AM
You need to ask David but imo with a rebuild with everything being as tight as it is that might be expected. The only thing I can think that it might be is the front bearing has preload on it instead of 0 lash.

Mike Puckett
09-13-2015, 01:47 PM
I've wondered that the pilot bearing may be causing the input shaft to windmill. I've started buffing the tip of the input shaft to be sure it's nice and smooth and putting some more grease into the bearing. How old is the clutch? Can you force it to slip in 5th gear?

dthompson
09-13-2015, 02:09 PM
the clutch is a centerforce dual friction. Its fairly new, a couple years old with only about 4k miles on it. Pilot bearing is the same age. What do you mean when you say, can i force it to slip in fifth gear? while idling on the jackstands, I can put it into any of the gears easily. the wheels seem to move a little bit going into gear only in first gear from what I can tell. Im not sure if the higher gears keep the wheel from spinning going into gear. It seems like something is making the input shaft spin. I didn't notice anything wrong with the tip of the input shaft, but I dont remember inspecting it closely either. I guess I need to pull the trans and check the input shaft and replace the pilot bearing (I already bought one just in case).

davec73
09-13-2015, 02:28 PM
the clutch is a centerforce dual friction. Its fairly new, a couple years old with only about 4k miles on it. Pilot bearing is the same age. What do you mean when you say, can i force it to slip in fifth gear? while idling on the jackstands, I can put it into any of the gears easily. the wheels seem to move a little bit going into gear only in first gear from what I can tell. Im not sure if the higher gears keep the wheel from spinning going into gear. It seems like something is making the input shaft spin. I didn't notice anything wrong with the tip of the input shaft, but I dont remember inspecting it closely either. I guess I need to pull the trans and check the input shaft and replace the pilot bearing (I already bought one just in case).I think you should drive it some and see if it gets better if there were something wrong with the pilot bearing it would be noisy with the clutch disenguaged.

dthompson
09-13-2015, 02:37 PM
thats why i was thinking the clutch disk was not sliding on the shaft properly. Ive read different opinions on whether you should grease the input shaft splines or not. I didn't because it seems like a bad idea to have grease sling off inside the clutch. it does not seem right for the wheels to move when the clutch is pressed. the input shaft has to be spinning when it should not be. I hate to drive it knowing this and mess something up worse.

davec73
09-13-2015, 03:01 PM
thats why i was thinking the clutch disk was not sliding on the shaft properly. Ive read different opinions on whether you should grease the input shaft splines or not. I didn't because it seems like a bad idea to have grease sling off inside the clutch. it does not seem right for the wheels to move when the clutch is pressed. the input shaft has to be spinning when it should not be. I hate to drive it knowing this and mess something up worse.I bet they wouldn't move with the slightest bit of force on them. greasing the input shaft could cause grease to get places it would do far more harm than good.

Rob91
09-13-2015, 04:11 PM
Will it spinn the wheels if you depress the clutch pedal and then wait 5-6 seconds before trying to engage 1st?
If it shifts fine after waiting a few seconds, then the input shaft has had time to come to rest and shifting should be effortless. If you try to engage a gear before the input shaft has come to rest then the braking force from the sync-ring will try to rotate the wheels slightly. This would then be normal behaviour. (I didn't see the video /not working on my browser).

davec73
09-13-2015, 04:26 PM
Will it spinn the wheels if you depress the clutch pedal and then wait 5-6 seconds before trying to engage 1st?
If it shifts fine after waiting a few seconds, then the input shaft has had time to come to rest and shifting should be effortless. If you try to engage a gear before the input shaft has come to rest then the braking force from the sync-ring will try to rotate the wheels slightly. This would then be normal behaviour. (I didn't see the video /not working on my browser).exactly what I was thinking

Mike Puckett
09-13-2015, 06:49 PM
To check for slippage in 5th drive it down the road at about 45mph and romp on the gas. If it's going to slip it'll do it then. Since you have a fairly new CF Dual Friction I doubt it's slipping. I'm inclined to also think you should put some miles on it and see if it loosens up.

dthompson
09-13-2015, 07:06 PM
So i tried it again this afternoon. If I wait about 10 seconds after pushing the clutch in, then put it in first gear the wheels do not spin. less than 10 seconds and it the wheels move a little bit.

Im going to take it off the jack stands and drive it this week like normal (normal minus the occasional romp) and see if that helps. As of today it probably has 40-50 miles on it since the rebuild. I can probably put another 150 miles on it this week. Plus the weather is supposed to be beautiful.

dthompson
09-17-2015, 11:10 PM
I ended up pulling the transmission back out in order to loosen the input shaft shim. It was tight enough that i could not move it in and out. I reduced the shim by about 0.007". enough so that i could feel the input shaft move in and out. My lack of experience with transmissions leaves me with a lot of questions. Is this normal? The transmission is in neutral, but there seems to be enough drag to spin the input and output shaft together. Obviously can stop it from spinning with my other hand... but I somewhat expected it to not spin.


https://www.youtube.com/watch?v=FeKSKlerL-w&feature=youtu.be

Rob91
09-18-2015, 04:24 AM
I can not say if the condition shown in the video is normal or not, but keep in mind the tapered bearing front and rear will cause some compression between the input and output shaft resulting in friction. There will also be some friction between counter shaft and output shaft. Friction in the system would actually make synchronizing quicker and shifting easier.

I would make sure the input shaft is shimmed to spec, as too much end play will also cause hard shifting.

Is your main problem shifting at high or low rpms?


A lot of useful info can be found here: http://www.rsgear.com/technical.aspx

davec73
09-18-2015, 05:49 PM
Spec is 003 to 001 lol

dthompson
09-18-2015, 06:19 PM
According to my service manual it is .002 to .006 for the main shaft and .006 to .010 for the countershaft.