T56 Transmission Disassembly Video - ALL VIDEOS NOW POSTED
02-11-2016, 06:50 AM
#21
Hmm... that would suck. Whole reason I like the LS2 is the good response in the low rpms. If I'm cruising low speeds 5th @ 25mph is very smooth and as long as there isn't a hill or a need to accelerate much I will put it in 6th at 40mph. I only have 128k miles but everything feels perfect like a new transmission.
02-11-2016, 11:12 AM
#22
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Hmm... that would suck. Whole reason I like the LS2 is the good response in the low rpms. If I'm cruising low speeds 5th @ 25mph is very smooth and as long as there isn't a hill or a need to accelerate much I will put it in 6th at 40mph. I only have 128k miles but everything feels perfect like a new transmission.
-Chris
At least nearly everything that's wrong with this car is upgradeable with aftermarket support. My wallet thinks differently though. Still better than a car payment (most days). 
02-11-2016, 04:58 PM
#25
Hmm... that would suck. Whole reason I like the LS2 is the good response in the low rpms. If I'm cruising low speeds 5th @ 25mph is very smooth and as long as there isn't a hill or a need to accelerate much I will put it in 6th at 40mph. I only have 128k miles but everything feels perfect like a new transmission.
02-21-2016, 01:06 PM
#27
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But our engine makes peak torque at around 4500 rpm.. And it makes less torque at 1800rpm than it does at 3000 rpm.
So I was merely contesting the idea that lugging around in low rpm is somehow the cause of this problem.
I believe the *cause* is that the gear starts off loose. Then, after that, the premise that driving in low rpm is somehow worse than driving in a higher rpm seems a bit flawed since our engine doesn't make peak torque until 4000+ rpm.
-Chris
02-21-2016, 02:38 PM
#28
I'm no engineer but in general I've always heard that the combustion process creates a pulse and at lower RPMs, these pulses aren't occurring frequently enough to cancel each other out. This creates a hammering affect that you can hear if you lug the car hard enough.
The higher the RPMs, the more of these pulsing events there are and the more likely they will be to cancel each other out as they reach a resonate frequency.
Without thinking too hard about it, I would also be concerned about lubrication as the t56 is "splash" lubricated so the lower the rpms, the less oil will be circulating through it.
Looking forward to part 2!
The higher the RPMs, the more of these pulsing events there are and the more likely they will be to cancel each other out as they reach a resonate frequency.
Without thinking too hard about it, I would also be concerned about lubrication as the t56 is "splash" lubricated so the lower the rpms, the less oil will be circulating through it.
Looking forward to part 2!
02-21-2016, 08:05 PM
#29
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I'm no engineer but in general I've always heard that the combustion process creates a pulse and at lower RPMs, these pulses aren't occurring frequently enough to cancel each other out. This creates a hammering affect that you can hear if you lug the car hard enough.
The higher the RPMs, the more of these pulsing events there are and the more likely they will be to cancel each other out as they reach a resonate frequency.
Without thinking too hard about it, I would also be concerned about lubrication as the t56 is "splash" lubricated so the lower the rpms, the less oil will be circulating through it.
The higher the RPMs, the more of these pulsing events there are and the more likely they will be to cancel each other out as they reach a resonate frequency.
Without thinking too hard about it, I would also be concerned about lubrication as the t56 is "splash" lubricated so the lower the rpms, the less oil will be circulating through it.
I suppose it might be true that as speeds approach near zero (for example 1 rotation per hour), then there is a chance of the oil not being sufficiently present on the gears - but at those speeds, you wouldn't use bath lubrication - certainly not with an oil viscosity like ATF.
At high speeds, there is a much greater chance of cavitation in bath systems, which would be the more pressing concern.
Also, for what it's worth, the mainshaft speed is fixed on vehicle speed (except for reverse), so whether you were in 5th/6th or 4th - at 45mph, the mainshaft is spinning at the same speed. Thus, if you were really concerned about mainshaft lubrication for 6th gear at 45mph, you should be similarly concerned about it in 4th gear at the higher engine rpm.
Hope that helps.
I'm aiming to have Part 2 put together this week. I'll post when it's up.
Thanks,
Chris
02-21-2016, 08:56 PM
#30
Also, for what it's worth, the mainshaft speed is fixed on vehicle speed (except for reverse), so whether you were in 5th/6th or 4th - at 45mph, the mainshaft is spinning at the same speed. Thus, if you were really concerned about mainshaft lubrication for 6th gear at 45mph, you should be similarly concerned about it in 4th gear at the higher engine rpm.
This is one heavy transmission and I'll do anything I can keep it in the car and off the work bench!
02-21-2016, 09:10 PM
#31
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Your vehicle speed determines the speed the mainshaft travels through the oil bath - not engine RPM. The vehicle is most likely only going to see high vehicle speeds in 5th and 6th gear, so those gears would be more likely to be the only ones of concern relative to cavitation in the oil from splash lubrication alone. The new cars with the 6060s have considerably higher top end speed than our V's, so the problem would certainly be more worrisome.
My point was simply that lugging the engine in 5th/6th in our cars doesn't make that problem any better or worse.
-Chris
02-22-2016, 10:37 AM
#32
Cavitation at those speeds makes sense. I just assumed they added the oil pump because the main shaft is turning that much faster and the splash oiling can't supply the capacity needed to keep up at these higher rotations.
I've also heard over the years that when slowing from high speeds, you want to keep the transmission in gear instead of slipping it into neutral to prevent oil starvation. I think this conversation pretty much confirms that theory on a T-56. Any thoughts?
I guess we'll agree to disagree on this one. 
Thanks for taking the time to do the video!
I've also heard over the years that when slowing from high speeds, you want to keep the transmission in gear instead of slipping it into neutral to prevent oil starvation. I think this conversation pretty much confirms that theory on a T-56. Any thoughts?
Thanks for taking the time to do the video!
02-22-2016, 12:33 PM
#33
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The countershaft will slow down if you put the car in neutral (and let off the gas), but I have a hard time believing that any parts of it would be oil starved as there's too much friction in the synchros for the gears on it to stop spinning completely - and there wouldn't be any loads going through it to matter. Not to mention that the mainshaft is going to be slinging oil everywhere (wonder if there's a video of the internals of a transmission actually operating?).
To be clear, I don't think you're doing any damage to the trans one way or another - but I think the logic doesn't hold for oil starvation for the way the T-56 operates.
Regards,
Chris
Last edited by srracer; 02-22-2016 at 01:39 PM.
02-22-2016, 12:38 PM
#34
Well, I'm not sure that would make sense for the T-56. As I said earlier, the mainshaft is fixed to the driveshaft, so it is spinning as long as the wheels are turning... Thus, whether your clutch is in or you're in neutral or not, the components on the mainshaft will be spinning directly in proportion to wheel speed and should therefore be adequately picking up oil as you decelerate from high speed.
The countershaft will slow down if you put the car in neutral, but I have a hard time believing that any parts of it would be oil starved as there's too much friction in the synchros for it to stop spinning completely - and there wouldn't be any loads going through it to matter. Not to mention that the mainshaft is going to be slinging oil everywhere (wonder if there's a video of the internals of a transmission actually operating?).
To be clear, I don't think you're doing any damage to the trans one way or another - but I think the logic doesn't hold for oil starvation for the way the T-56 operates.
Regards,
Chris
The countershaft will slow down if you put the car in neutral, but I have a hard time believing that any parts of it would be oil starved as there's too much friction in the synchros for it to stop spinning completely - and there wouldn't be any loads going through it to matter. Not to mention that the mainshaft is going to be slinging oil everywhere (wonder if there's a video of the internals of a transmission actually operating?).
To be clear, I don't think you're doing any damage to the trans one way or another - but I think the logic doesn't hold for oil starvation for the way the T-56 operates.
Regards,
Chris
04-06-2016, 08:55 AM
#35
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Chris, I really appreciate your videos! They gave me the courage to tackle the rebuild myself. I just bought a 04 CTSV that has a vibration in 5th and 6th, with only 80k. When I took it apart I found the splines on the 5-6 cluster and main shaft were almost completely gone!
I had my trans completely back together when I found a nice little washer on the ground of my garage. It is identical to the washer for the 6th gear needle bearing set.
Can you confirm for me that 6th gear needle bearing has TWO washers? One on top and one below? I want to make sure that I put it back in the right place. I can see in your video that when you pick up the 6th gear needle bearing that you drop the washer, so there must be one below, and all other T-56 trans seem to have one above.
Thanks again!
I had my trans completely back together when I found a nice little washer on the ground of my garage. It is identical to the washer for the 6th gear needle bearing set.
Can you confirm for me that 6th gear needle bearing has TWO washers? One on top and one below? I want to make sure that I put it back in the right place. I can see in your video that when you pick up the 6th gear needle bearing that you drop the washer, so there must be one below, and all other T-56 trans seem to have one above.
Thanks again!
04-06-2016, 11:17 AM
#38
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Hmm.. good catch. When I disassembled, I kept everything together in the exact order they came out of the case, so the reassembly was very straight forward. I never noticed until now that the manual doesn't show that washer. Not having the transmission disassembled in front of me, I can't really confirm that the washer at that point in the video is the same size as the one on the top, but the video is some evidence that a transmission from the factory has a washer there.
That said, it strikes me that the lack of that washer would have *probably* shown up in the countershaft extension clearance process (assuming it acts as a thrust washer). Did you double check the countershaft extension clearances after reassembly?
-Chris
That said, it strikes me that the lack of that washer would have *probably* shown up in the countershaft extension clearance process (assuming it acts as a thrust washer). Did you double check the countershaft extension clearances after reassembly?
-Chris
04-06-2016, 11:36 AM
#39
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Hmm.. good catch. When I disassembled, I kept everything together in the exact order they came out of the case, so the reassembly was very straight forward. I never noticed until now that the manual doesn't show that washer. Not having the transmission disassembled in front of me, I can't really confirm that the washer at that point in the video is the same size as the one on the top, but the video is some evidence that a transmission from the factory has a washer there.
That said, it strikes me that the lack of that washer would have *probably* shown up in the countershaft extension clearance process (assuming it acts as a thrust washer). Did you double check the countershaft extension clearances after reassembly?
-Chris
That said, it strikes me that the lack of that washer would have *probably* shown up in the countershaft extension clearance process (assuming it acts as a thrust washer). Did you double check the countershaft extension clearances after reassembly?
-Chris
Looking closer at your video (at 5:46) I see the top and bottom washers now, I must have dropped the bottom one when I was pulling it apart, and I am certain the washer I found on my floor belongs below the 6th gear needle bearing.
I am pretty certain that those washers do not carry any thrust, they are only there to make sure that the needle bearing carrier does not wear against the the snap ring on top, or the counter shaft end on the bottom. They also did not appear to have any wear on them. So it may not have an affect on the end play, although, when fully assembled, the washer did sit very slightly higher than the 6th gear.
04-07-2016, 02:13 PM
#40
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Hey gang,
I finally finished all the videos for the T56 rebuild. Not perfect, but I'd like to think that at the moment they may be some of the better ones out there. Enjoy!
Part 1 - Initial tear down of the T56 Transmission: Part 2 - Rebuild of mainshaft assembly: Part 3 - Setting the mainshaft and countershaft clearances: Part 4 - Final Assembly and Countershaft extension clearance:
Hope these are helpful to anybody considering tackling this by themselves!
-Chris
I finally finished all the videos for the T56 rebuild. Not perfect, but I'd like to think that at the moment they may be some of the better ones out there. Enjoy!
Part 1 - Initial tear down of the T56 Transmission:
Hope these are helpful to anybody considering tackling this by themselves!
-Chris