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TKO 600 Upgrade?

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Old Feb 3, 2024 | 05:13 PM
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Default TKO 600 Upgrade?

I bought my TKO 600 about 12 years ago. Still in the box, waiting for a break in life to finally get it put into the car. Since more than a decade has passed, I’m wondering if there are any recommended modifications I might consider before I install it because once it’s in the car, I have no plans of ever removing it so if there ever was a time for opportunity, it is now.

To be clear, this car will be babied. Yes, I have 500+ HP/torque on tap but zero plans to abuse it so I’m not looking for changes that will allow me to, say, shift at 6000 RPM and the like but if there are sensible mods to generally improve my experience with it, I’d appreciate all inputs.
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Old Feb 3, 2024 | 05:25 PM
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I installed my TKO 600 almost that long ago with no modifications and it works beautifully. The only mods I am aware of involve the synchros as the trans has a bit of a reputation for not shifting smoothly. I did find the trans was a little challenging to shift when it was new, but after a couple thousand miles it smoothed right out. I probably have about 10,000 miles on it now and its smooth as silk. The only complaint I have is it leaks like the proverbial sieve. I have always added a couple hundred cc's of oil every season to keep it topped up. Last year I decided to put some dye in it to see exactly where it was leaking. Long story short, everywhere.
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Old Feb 3, 2024 | 06:18 PM
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I also put mine in many years ago, and it has worked flawlessly for me....totally transformed the car into a blast to drive compared to the 4 speed. I spent a lot of time driving on the highways back then so the overdrive was really welcomed.
As for modifications, If you drive it as you say you will, you'll have zero issues. I've had mine to the dragstrip, and was shifting at 6500 RPM and only missed that 2-3 shift once....then I figured out how to do it...no issues since.

I'm pretty sure you'll ask yourself why I waited so long to put it in....
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Old Feb 3, 2024 | 09:19 PM
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@drwet Thanks. Leaking badly? That is very disappointing to hear. My dad rode Harleys for 50+ years and there always was a drip pan underneath it. I do NOT want to experience that. Maybe first order of business is to seal all the seams?
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Old Feb 3, 2024 | 09:20 PM
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@OMF Thanks for the input!
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Old Feb 3, 2024 | 10:32 PM
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I had a TKO600 and they shift like a hot knife cutting butter . very smooth tran
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Old Feb 4, 2024 | 10:47 AM
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Originally Posted by 69L88
@drwet Thanks. Leaking badly? That is very disappointing to hear. My dad rode Harleys for 50+ years and there always was a drip pan underneath it. I do NOT want to experience that. Maybe first order of business is to seal all the seams?
How do you know when a Harley is out of oil? It stops dripping.
I use the same approach with my trans. Not sure what the solution is, but yes, virtually every seam and seal in the transmission is seeping lubricant. I figure one of these days I am going to have to pull the trans and have someone replace all the seals and gaskets. I am reluctant to attempt it myself, and I am even more reluctant to let someone else open it up. In the meantime I live with it. As to why it is happening, I'm not sure. There was a time when synthetic lubricants had a reputation for seeping past seals and gaskets. Perhaps there is some truth to that and I have one of the susceptible components. (I did have a 2001 KLR 650 that had that problem.) I do run Amsoil synthetic in my TKO 600.
Sorry I can't offer much help beyond relating my experience.
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Old Feb 4, 2024 | 12:19 PM
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I installed my TKO-600 in 2006. No leaks at all, still shifts very smoothly. There is about 30+K miles on the transmission now.

I purchased from Keisler's. I remember some advertising from them at the time, that stated they took all the transmissions apart and reassembled, for some reason.
Maybe they're the ones that don't leak.
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Old Feb 4, 2024 | 02:43 PM
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Originally Posted by Barry's70LT1
I installed my TKO-600 in 2006. No leaks at all, still shifts very smoothly. There is about 30+K miles on the transmission now.

I purchased from Keisler's. I remember some advertising from them at the time, that stated they took all the transmissions apart and reassembled, for some reason.
Maybe they're the ones that don't leak.
Thanks, that’s a good datapoint.
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Old Feb 4, 2024 | 02:51 PM
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I also have a 12 year old Keisler TKO 600. Good news, not leaking. Bad news, hasn't been installed in GSX yet. Hope both get installed sooner than later.
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Old Feb 4, 2024 | 08:28 PM
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Originally Posted by drwet
I installed my TKO 600 almost that long ago with no modifications and it works beautifully. The only mods I am aware of involve the synchros as the trans has a bit of a reputation for not shifting smoothly. I did find the trans was a little challenging to shift when it was new, but after a couple thousand miles it smoothed right out. I probably have about 10,000 miles on it now and its smooth as silk. The only complaint I have is it leaks like the proverbial sieve. I have always added a couple hundred cc's of oil every season to keep it topped up. Last year I decided to put some dye in it to see exactly where it was leaking. Long story short, everywhere.
Interesting that yours leaks all over, as mine has been tight as a drum since new......now wait a minute, I just remembered that mine leaked at the rear yolk right away, sprayed oil everywhere around the u-joint. After cleaning it all with brakecleen, I took it around the patch and discovered that the cup that seals the yolk was leaking. I took the driveshaft off and removed the yolk, sealed it up and it's been dry ever since.
My tranny was just the same....a little notchy for the first 1000 miles and then smooth as butter since.
I bought mine through "ClassicChevy5Speeds"
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Old Feb 4, 2024 | 09:11 PM
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I put a 600 TKO in my 73 Camaro with a LS3. It was a bit notchy on the 2-3 shift. But I'm comparing it to the T56 Magnum I had in my 68 C10 LS swap. The TKO never leaked. I did have to mod the trans tunnel due to the fact the top of the 600 is kind square on the top.
Don't know if it's an option for you but the Tremec TKX 5 speed has become popular due to it's more compact size.
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Old Feb 4, 2024 | 10:12 PM
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I have installed 2 TKO-600's. One in my 1973 Corvette and one in my 1955 Chevrolet. Both are great and have had no problems. I did damage the rear seal on the one in the Corvette during installation, Found a seal locally and both have been leak free. I got the .82 5th gear. I did the 55 Chevy first about 6 years ago and the 73 Corvette 3 years ago.
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Old Feb 4, 2024 | 10:15 PM
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Originally Posted by 71 Vert LS1
I put a 600 TKO in my 73 Camaro with a LS3. It was a bit notchy on the 2-3 shift. But I'm comparing it to the T56 Magnum I had in my 68 C10 LS swap. The TKO never leaked. I did have to mod the trans tunnel due to the fact the top of the 600 is kind square on the top.
Don't know if it's an option for you but the Tremec TKX 5 speed has become popular due to it's more compact size.
Thanks. I thought about the TKX but for the amount of miles I will be putting on the car, coupled with the fact that the TKO has a good history (reports of leaks not withstanding), I’ll be good with it, avoiding all the hassle of selling it, buying the TKX, shipping, etc., etc.
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