I have a Brand new Tremec TKO 600 that's been upgraded with Carbonfiber blocker rings for better high RPM shift quality,this job got done by Keisler before I got the transmission. My problem is that it grinds when i shift from 3rd to 4th and downshifting from 5th to 4th Even in low RPM.
What can the problem be?

Please help.

What fluid are you running in it?....

Just for background, was the upgrade a repair or is this the first time ever for the tranny in a car?
To THO users, does this tranny break in at all and improve with time?

Its in Norway? Ouch.

Mine was bone stock as Tremec built it and high rpm shift quality sucked. Period.

It never 'broke in' like promised.

Light throttle casual driving it shifted like butter, but when I got on it and the RPMs were up, it was like trying to shift without a clutch

The T56 I have now shifts great at any RPM

Running GM synchromesh witch is recomended by Tremec

the transmission was band new and the upgrade was done before the first tme install.

My bud has one of those behind a 528 roller hemi. He has broke it twice and done all the upgrades. It shifts like a Mack truck. I would not own one of those.

Hi, Erik, sorry to hear about this. Did you buy it from Keisler direct, or through a Norwegian company? I know Anders Ringstad has imported some of these gearboxes, and maybe he can assist you in some way? I am currently putting a 5 speed Keisler behind a 440 for a client, and there have been some issues with lacking hardware and non fitting parts. Hope this gearbox works! What sort of car do you have?

Kind regards from Norway.

thanks a lot for the advice Øyvind, I know Aanders well ans that was sort of my back up plan. the tranny is sitting in my 1970 cuda.

I have a 600 new still in the box, intended use was non competitive road race, likely never above 6K shifts, but a missed shift up or down on a road race car usually means the guard rails get real close and friendly. Everyone knows what they cost brand new, is it usable, or just suck it up and dump it and bypass all the aggravation?

I tried syncromesh and ATF. Neither one had any affect on poor shifting.

Up to this date. I've never seen a TKO600 shifted fast at high rpm.

If anyone ever has or seen it. Prove it here with an in car video. I hear the 500's are not much better.

Thanks for the info Mike! The thing is that the problem is There Even in low RPM shifts. I have also used dextron III but with the same poor result on olnly on up shift to 4th and from 5th to 4th.
What weight oil should i try?
What's the name of the company that do the blocker ring upgrades for Keisler?

Hello
My TKO 600 also is hard to shift and a little slow but does not grind. I run carbon sync rings from Liberty. What I just found is that the clutch is not disengaging properly. I had the clutch pedal throw adjusted to one inch beyond the point where the rear wheels were not moving when on stands. I had to adjust in quite a bit more clutch throw to free the shifts. This made a huge difference in the way it shifts. This resulted in a pedal throw too long for my likings so I have to dig into a clutch/release issue here. Just wanted to share as this tells that some drag is taken up inside the trans and can mask a small lack of clutch release. I have only used syncromesh after upgrading to carbon rings. I tried both atf and syncromesh with the standard rings without any notisable difference. Good luck!