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Manual trans swap tko, t56, or.....?

Boom

Boom

Well-Known Member
Donator
I'm looking to swap the C4 out of my 68 and have been trying to look into whats involved with various setups. Most of the info I find is old or uncertain.

It would be going behind a 351w/408. So a T5 is pretty much out. I also have RM drop mounts.

I've been leaning towards a TKO600 with the .64 OD. I'd like to do a T56 but it seems like alot for work with tunnel mods and everything costs more for it.

What are you guys thoughts?
 
You can build a T5 that will live there just fine and it fits without all the metal cutting the bigger trans require. I flog mine pretty hard all the time without an issue, yet. As long as you don't plan on slicks and track visits T5's can take a lot. Spend some money on parts like those from Astro and they can be just as rugged, even more so than a stock TKO. Who needs a 6 speed?!
 
I've heard all the great things about Astro and G force but I've also heard the horror stories. My old coupe had a 302/T5 and I loved it. A T5 would be nice if I knew that it'd last.

I actually have been reading the same story with my Iroc on the T5 issue. Some say it'll last just fine, others say it'll snap reversing out the driveway.

I'll look at what they have currently, bit I think astro quoted me like 3400 or something a few years back just for a bare trans.


Edit: I found a place alled Pro Force Transmission, they offer the a T5 with the Astro bits for only like 2200. I sent that an email asking for more info. Seems almost too good to be true. That would make it a much easier swap for sure.
 
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From my perspective, most of the "horror stories" from internet forums about anything are usually the result of their own doing that they try to frame as the fault of some manufacturer or part. Not always but typically. Plus you have all the other guys who can't wait to scream "me too!"
 
Yeah, you can find horror stories for just about everything out there. Part of me wonders though. If it were easy to get the T5 to reliably handle the same power as a tko, why make a tko at all?

I remember reading into the astro stuff years back and just never felt comfortable dropping that much on a trans that could be picked up for 3-400 on Craigslist. Obviously without the voodoo going on inside. I figured if it ever broke I could pick up another (or 3) and still be ahead.

The T5 is definitely the easiest and possibly cheapest to install. With the exception of the astro obviously.
 
Behind a 408 go with a tko. With a hot 351w you’ll be pushing the torque limits of a t5. Can it be built to last? Of course, but it will always be the weak link. Do it once and do it right with a tko, considering 500 horse is pretty easy with a 408.


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^ I agree with that.

You can totally build a decent T5 that will stand up to street duty behind a moderate Windsor build, but it will always be a bit of a weak link if you can get traction.

I actually have an Astroperformance A5 I'm rebuilding right now for install behind my 331. The gears are definitely beefy, but the case and output shaft are still weak points behind high torque motors. I wouldn't buy an A5 outright, as a TKO or T56 is a much better option for the money.

The reason I didn't look at TKOs is because they don't like high rpm shifting, and my 331 winds to 6k+. But not too many 351Ws spin that fast, so I'd worry more about torque capacity in your case.
 
Heard back from the shop about the Astros. Said that Astro is super behind right now. Last one they ordered took about 11 months to ship.

I'm probably going to order the other bits and bobs for the setup. I'm still leaning towards the tko most likely. There's a good grand worth of parts just in the bellhousing and clutch area to get first.
 
Third option is the one I'm on. Run a T5. IF it breaks, fix it and do it again. :p So far banging shifts at over 5k and things are holding up just fine behind a very stout 347. Got a second T5 sitting under the bench just in case. At least until the truck needs it.
 
If you do build a T5, there is an aftermarket countershaft bearing retainer that helps prevent case flex, which is one of the things that tends to destroy gears.
 
I dont want to have to keep replacing the transmission. I can't get past the point that if if was 1000% reliably doable, tremec would've released a super T5 of their own. But they haven't. They've even released a beefed up T56 specifically for 82-02 F-bodies just last year. So its not that they aren't looking at the older stuff.

Plus the fact that nothing swaps between them besides the clutch.

The only con I seem to find on the tkos is that they sometimes have issues shifting over 5k rpms. I don't plan to ever shift that high anyway, so its a non-issue for me.
 
Yeah, that's the reason I went with a T5 instead of the TKO: high rpm shifts.

Do keep in mind that the tunnel may need a bit of massaging to clear the TKO.
 
I have a T5 in my 67. I like it but the TKO600 in my 65 was awesome. Much stronger.

The 6 spd in my 18 GT350 is the best. Only issue is sixth gear is way high.

If I had my 67 to do over I'd put a six spd in it.

Mel

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I have read that the tko may need the tunnel support flattened.

I'd love a 6 speed, but it does cost quite a bit more plus the tunnel mods required.
 
So I've waited but no one came forward so I'll just ask. Has anyone here broken a T5 because it couldn't handle the torque put through it? If so,what happened? Were you at the track? I'm not saying it can't happen as it surely can. Anything can break. Keep hearing how one has to go with a TKO but no real evidence AT ALL of it being necessary with a street car. The cost can be significantly higher so it would seem justification is warranted. Hacking up the floor and spending cash needlessly seems rather silly.

I run about as built a 347 as one can build. Never been on a dyno but similar builds that have are always nearing or even surpassing 500 hp and very similar torque numbers. Let's be conservative and say 400/400 for argument sake. I beat the ever lovin' crap out of it every time I take it out. If I get the first row at a light YOU KNOW I'm hammering it through the gears and shifting at 5k. My suspension is also set to lay the power to the ground so I do not see much wheel slip at all. Point being a mildly worked over T5 can survive just fine and slips right into a stock space. Did I mention how nicely it shifts too?

I also don't get the 6 speed love. Help me understand. For spirited driving what could be better than a 4 speed with an over-drive? Why do I need yet another gear? I've run my car up to 140 with a 5 speed and the engine speed was just fine. It's not like one cruises down the highway at 120 for hours at a time. Seems like a huge waste of money to me. The only real modern trans I would consider would be a worked over automatic, to be honest, for absolute best times at the drag strip and long haul cruises.
 
I have always heard anecdotal accounts of how T5's can't handle the power and torque, I have not however heard any true first hand experience with a failure. We probably have similar output motors and I too hammer the living daylight out of the car when I drive it. So far it has lasted almost 9 years with zero issues. Hard take offs, high rev shifting, nothing seems to hurt it. While I built it with a few minor upgrades, I probably have less than $1K in the entire trans.....pretty good investment by my book!
 
I've talked to a couple fox body guys locally who have broken T5s behind healthy 5.0s, and a couple people on forums who have broken them behind stroker motors.

In my research, there appear to be a few major (relatively) weak points for T5s:
1) lack of internal shift stops. Most people use stock shifters (Also without stops) and bang them through shifts, which can easily result in bent shift forks, which will quickly result in Bad Things. This is basically user error. I have a Pro 5.0 shifter on mine with adjustable stops which should prevent this issue.

2) 2-3 shift with high torque and stock gears. The stock gears have an aggressive helix angle which can cause a lot of opposing force between the mainshaft and the countershaft. The stock T5 case isn't terribly strong in this respect, nor is the stock countershaft rear bearing retainer, which can allow the two shafts to walk and spread slightly, causing Bad Things. Behind a mild small block, it's probably not an issue. But a decent stroker or Windsor can cause problems. This can be mitigated with aftermarket gears with less helix angle, as well as an improved billet aluminum countershaft bearing retainer.

3) Main shaft. I've talked to a few people who have snapped a mainshaft. Not during spirited driving, but I'm sure it was a progressive failure that started with a high torque impact load. I don't know that I'd worry about this until you get into drag racing, and at that point, maybe you should be looking at something more stout to begin with.
 
I have not experienced any first hand damage myself either. I think its most likely good, but there has to be good chance of something breaking, because neither Ford or GM used a T5 behind anything bigger then a 302 or 305. Even the one year only 95 Cobra R got a TKO and that car was only rated at 300 hp and 365 ft/lb.

Maybe everyone is playing with fire or the big companies just don't like the margin of potential error. There has to be a reason. If it was simply a matter of installing better gears and a couple bolt on billet supports dont you think Tremec would've done that themselves? Or GM? Or Ford? Instead of redesigning everything for a different transmission.

I've held off on purchasing any trans specific parts myself, in hopes i can decide one way or another. With the Astro A5s being the same price about as a new TKO, there's no reason not to get a TKO. At least on a 67-68. I hear the earlier cars have to trim quite a bit.
 
I had 2 in my garage with cracked cases. The rear cluster support is extremely weak. I didn’t say you can’t build one to hold up but if your even considering going Astro or someone like that why would you not go tko.


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Oh and BTW, as you guys know the t5 is an ancient design. It was originally a 4 speed hence the 5th being placed outside the main case.


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