Help! Can't shift T56 to reverse after replacing reverse fork pads - LS1TECH - Camaro and Firebird Forum Discussion



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Help! Can't shift T56 to reverse after replacing reverse fork pads

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Old 03-16-2017, 12:07 AM   #1
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Default Help! Can't shift T56 to reverse after replacing reverse fork pads

Ever since I picked up my 2005 CTS-V it has had trouble shifting into reverse. When I bought it, I optimistically thought it was the shift bushings, but it turned out to be the reasonably common problem of worn fork pads coupled with insufficient fork throw.

bigassogre posted a how-to for fixing the problem here, which involves pulling the tail housing with the trans still in the car. I went through the process (including shaving and shimming the reverse fork), replaced the fork pads, reassembled the housing, and put fluid in it. As I was reassembling the shifter I noticed that it was difficult to move to the right towards 5/6 and reverse. After a little wiggling, it would consistently get to 5/6 without much resistance, but no amount of wiggling will persuade it over to reverse.

Any thoughts on what I might have borked in the reassembly? I see three possible problems, but I'd like some input before I disassemble everything again.
1. I thought I was careful to put everything back in the correct order, but I might have gotten something wrong.
2. bigassogre suggests pushing the upper rod out of the way to remove reverse - I could have perhaps pushed it too far and bent something
3. the tail housing was being difficult to reinstall, and I ended up adding a tiny bit of chamfer to the hole in the tail housing to encourage the reverse fork rail to find its home. It's possible I might have tweaked the shift rail in my attempts to get the housing to seat before I added the chamfer.

In case you can't tell, transmissions are not my specialty. What should I be looking for when I tear it out again? What could cause this problem?
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Old 03-16-2017, 12:41 AM   #2
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Oh, one more thing. I flipped the reverse syncro to use the side with fresh teeth. Might be related.
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Old 03-16-2017, 02:33 PM   #3
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Hmm... I started the engine with no driveshaft connected to see if I could select reverse (no dice) and the trans makes a buzzing noise when the clutch is released, almost as if something is rubbing on gear teeth like a baseball card in bicycle spokes. I'm guessing I must have reassembled something incorrectly rather than it being a shift rail issue.
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Old 03-16-2017, 07:49 PM   #4
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At the risk of having a conversation with myself...
I popped it open again, and even with no reverse fork in place it still won't shift to reverse which means I probably borked the shift rod while reinstalling the rear housing.

I also removed sixth gear and its fork and the shift rod seems to be just floating around in there with nothing holding it in place. Is that normal?
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Old 03-16-2017, 09:42 PM   #5
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In the T56, the shift rods for 5-6 and R are supported by the front adapter plate and the extension housing. Their rotational alignment is secured by the RH vertical case alignment bolt. There isn't something holding it fore and aft except for the selector pin interlock sleeve, maybe your R shaft was forward on reassembly. Take it apart, when reassembling this time, make sure R is in it's new slightly rearward "neutral," 5-6 is in neutral, and use a thin blade to support the rail so it properly hits the bore in the extension housing. And good luck working 115 degrees out of vertical
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Old 03-17-2017, 03:01 PM   #6
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Thanks Matthew.

I have an admission. I should have mentioned this from the start, but I guess I was too embarrassed to say so. When I was reassembling the tail housing the first time, it wouldn't sit flush with the main housing. I thought it might just be getting caught up on the dowels, so I very carefully started tightening the tail housing bolts to see if it would pop into place. Yes, I know that's a terrible idea and can often result in a broken housing, but I had sealant drying and I was frustrated and I did it anyway. Sure enough, without having to tighten the bolts very much, it "popped" into place. I realize now that was the reverse shift rail popping in place and not the dowels.

I've been fighting with this for three days now, and I just can't seem to get it working. I have discovered that with the reverse shift shaft floating in the housing (not aligned with the front adapter plate hole or the tail housing) I can get the shifter into reverse. If I put the shifter in neutral and then install the reverse shift shaft, the shifter won't go over to reverse. If I put the shifter in reverse then install the shaft, I can shift to reverse but the shaft doesn't move.

I think I've somehow slipped the alignment of the selector pin and the shaft or possibly bent the pin. I've gotten in there with a scope and I can't see any broken parts, so that's good. I've been watching T56 disassembly videos to try to visualize what's going on inside with the shafts, it's pretty difficult to connect what's going on with my shafts to what I'm seeing in disassembled trannys.

I'm getting close to just removing the whole trans from the car and disassembling it, but I'm working on jackstands and I don't have much in the way of gear pullers or other trans tools so I'm really hoping to fix it with the trans still in the car.
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Old 03-17-2017, 04:11 PM   #7
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The shift rods and alignment can be tricky on assembly, but it sounds like you need to pull the trans back apart to make sure it's together right.
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Old 03-17-2017, 07:08 PM   #8
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Yeah, I just went ahead and pulled the trans out. It wasn't that much work given how much was already disassembled on the car. I'm just about to remove the housing to see what's happening.
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Old 03-17-2017, 08:30 PM   #9
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As I feared, the "pop" wasn't a good one at all. Anyone know what the part number would be for this lil' fella?




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Old 03-17-2017, 09:40 PM   #10
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Old 03-17-2017, 09:41 PM   #11
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Google T56 Shift Rail Interlock Camaro and you'll find it.
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Old 03-17-2017, 10:21 PM   #12
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Thanks gents. Hopefully I can get one quickly, as this car is my DD.
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Old 03-17-2017, 10:28 PM   #13
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12523212 and prime shipping might suit you then.
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Old 03-18-2017, 01:20 AM   #14
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That's an appealing option, but I'm on the wrong side of the 49th parallel to make that as quick as I'd like. I'll see what I can find from local suppliers on Monday, and hopefully I won't be gouged too badly.
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Old 03-18-2017, 01:27 PM   #15
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So much for Prime shipping. "Typically ships in one to two months".
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Old 03-29-2017, 02:21 PM   #16
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Got it from Tick with express shipping. Installed and things are now shifting like a champ.

Unfortunately I didn't mark the driveshaft and flanges for phasing, so now I have a shaft vibration at 70+ mph. I'll have to try clocking it when I have some time. Is it more likely to be misaligned at the pinion or the trans flange? Or perhaps the carrier bearing is not perpendicular to the shaft?

I can see this being a time-consuming experiment to find the setup with minimum vibration, so any tips would be appreciated!
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