6L90 option for G8- fitting for...for next trans failure

[gr8lover]

Going to do a test fit and check for a 6L90 in my G8 tomorrow. Have it all ready to go--- trans out......... 6L90 TCH/Case/extension all set to be fitted...

It appears to me that there is no issue fitting it into the car (minus the obvious Driveshaft shortening required, trans mount modifications, end of driveshaft..)

I think all I need to do is the following to make it work:

• Shorten driveshaft or make new-- with new new end
• modifiy mount-- will size up-- buy new mount and then modify to work-- not that bad...
• replace 6L90 Valvebody TEHCM with the original g8 TEHCM
• upgrade 6L90E with aftermarket clutches

The body of the case is slightly taller by maybe a 1/8" (and a slightly different slope) and the length is longer on 6L90.... everything else is same..... Torque converter housing is identical! Mounting is identical in front, Manual shaft is in exactly same positon and location, connections same location (easy fit)...

once I get mount figured out, this is my plan for after the rebuild goes.... I think a aftermarket 6L90 is the answer for many of us.... it is much stronger stock than the 6L80 and more opportunities for better aftermarket upgrades on it....

Included are some pics of the two cases (TCH is identical and is not included in pic



Dont look at extension on the 6L90 case.... i didnt put the extension on the 6L80 case so disregard relating to the difference.....

[norm8332]

Nice, How much power are you planning on putting through it?

[parish8]

hmm, didn't know there was any diference in the case.

i like where you are going with this. looks like an easy swap to me.

what does a 6l90e come in?

[bbradyc5]

hmm, didn't know there was any diference in the case.

i like where you are going with this. looks like an easy swap to me.

what does a 6l90e come in?

Think it comes in the CTS-V and STS-V cars .... not sure what else though....maybe some HD trucks

[vic2186]

What happend to your circle d tranny??

[1stGXPmaggie2.3]

gr8lover, do the 6l90 transmissions have more clutches or are they larger clutches. What aftermarket parts are you aware of that better the 6l90. If so then sounds like a great mod upgrade.

[gr8lover]

What happend to your circle d tranny??

The circle D tranny should arrive all upgraded tomorrow... I am excited about it but I guess I am looking for future options.. It was a good chance to check on this and figure it out now so if it happens again and have issues, I may just do the 6L90 upgrade with upgraded clutches and then I shouldnt ever have to worry about it... I guess I am still a bit worried on how much the upgrades will help. I am hoping for the best but looking for plans in the future.

[vic2186]

Cool bean!!keep us updated,,

[gr8lover]

gr8lover, do the 6l90 transmissions have more clutches or are they larger clutches. What aftermarket parts are you aware of that better the 6l90. If so then sounds like a great mod upgrade.

I dont have my cheat sheet with me now but the 6L90 has more clutch plates then the 6L80 and the opportunity for a much better clutch plate setup.... the 6L80 clutches surface area increased something like 50-75% with the upgrade, but the 6L90, already has significantly more and then more on top of that can be added.... also, the Output carrier is significantly larger with much larger pinions and sun gears, etc.., input carrier has 6 pinions vs 4(i upgraded this in my 6L80 already..) some of shafts are significantly larger..., case has more supports and ribbing for rigidity.... and there are things that not many people or "publications" see that make it a much stronger unit than the 6L80.... I will have to get a good list soon..... I seen some before but none of them include all the little things different....

[SinCity G8]

Thanks for being the first to try this. Is this the same tranny that is in the L99 Camaros?