Fox Tko Or Astro

Mucka

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Dec 21, 2014
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So I have an 89 foxbody 347stroker 344 rwhp stock tranny 3rd is gone need to upgrade am thinking of a TKO also heard of the Astro t5 but seems just as pricey as doing the TKO if I go with the TKO I will need? Crossmember, bellhousing? What else is needed clutch? Any info appreciated
 
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Welcome to the forum. Your question has been covered bajillion times here, and before someone gives you crap, I'll say this. If you look up at the top of the page at the search bar and type in "tko or astro", you'll find pages of the answers, everyone's experiences and opinions. Happy reading.
 
The cost is about the same once you factor in the different bellhousing and crossmember. Both will need a 26 spline clutch. The TKO is a proven unit, but the A5 is supposed to be BAD! I wish I had found one before I bought my g force. The A5 is supposed to shift like butter compared to the TKO.

Joe
 
Put a TKO beside ANY T5 and you'll see that the TKO has a bigger, stronger transmission case. The primary issue with all T5 versions is that under extreme loads, the case starts to spread. This shifts the load on the gears from the center of the gear wear pattern to the tip area. Then the gear teeth start to overload, wear excessively, and ultimately fail

Tremec TKO - notice the width of the gears.
7464c5a07756ba81.jpg
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T5 - notice the gear widths, be aware that is a much closer picture that the one above, so it takes some thought to get the right perspective.
Diagrams courtesy of Tmoss & Stang&2birds
5_Speed_Cutaway_Illustrated.jpg


All other things being equal, the wider gears will transmit more power with fewer problems. Add the additional case strength, and the TKO a better choice. The TKO is roughly 25 pounds heavier than the T5, and that 25 pounds is the extra metal in the gears and transmission case.

For those with concerns about the shifting, I have a Tremec 3550, the precursor to the TKO and it shifts very well, smooth and fast. Use the proper lubricant and break it in correctly, and it is a great choice for a high performance transmission.
 
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What does the tremec 3550 call for oil anyway? I have a tremec t5z now I think i used synthetic atf, slightly less than 3 quarts, the next build will be a stouter 3550 or better, what do the bad boy Trannys call for?
 
Not sure on the TKO and 3550, but the T5 variations (g force, A5) use a mix of synthetic ATF and another specialty gear oil. I forget the name, but it was about $16 a quart.

Joe
 
That's good to know, I will eventually lay down the coin for a beefier gearbox and didn't mean to go off topic or steal anyone's posting, I hear nothing but good things about tko 5/6 I don't know anyone who runs an astro so I can't say, my buddy's 3550 has been put thru some abuse at e-town "raceway park" without a lick of trouble, but i would like to find out more about the astro just to know, good luck with it all
 
What does the tremec 3550 call for oil anyway? I have a tremec t5z now I think i used synthetic atf, slightly less than 3 quarts, the next build will be a stouter 3550 or better, what do the bad boy Trannys call for?
3550 uses gm synchromesh

Also, a 3550 can be upgraded to a tko very cheaply
 
I'm with jricker, smart money buys the tko.

At $2800 to get 25ftlbs torque capacity less, it's kinda insane to buy an astro
 
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ill be swapping my pos t5 with a 1st-gen tko over the winter, ill try to keep up to date with it. the first 500's and 600's had more shift issues than the original tko/3550, but supposedly has been resolved by tremec now (fiber-lined blocker rings) and some vendors fiddle around with the shift rails for even better shifting, and some offer faceplating.

as noted, it needs synchromesh fluid (supposedly pennzoil makes the stuff), and it needs a different bell (same casting as far as i can tell, just different bolt pattern), 26-spline vs 10-spline clutch, and 31-spline vs 28-spline driveshaft yoke. can use the same crossmember as the t5/aod, just cut the tack welds on the tubes and slide it back. other than that, it's really just a bolt in.
 
I agree with 25th The 3550 is a good trans but no where as smooth shifting as the T5

The TKO I had in a mod car felt less smooth than the 3550

Hell I would go so far as to say my t56 is not as smooth shifting as my stock T5 was
 
I've always heard the 3550 and tko were not as smooth to shift. Having had all 3 in a dd fox, the difference has been negligible IMO. I love the hell outta my 3550. Glad it was one of the first things I did to my current coupe.
 
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The shifting on the 3550 series is reasonable. It gets a little tough at high rpm (6500+). Fiber lined blocker rings fix the problem. It's about $1000 to upgrade a 3550 to a TKO.

Kurt
 
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The SPEC 3+ is actually a little smoother than the regular 3. We are a SPEC dealer, but honestly you are better off going through SPEC directly, because you will end up paying more through us than directly through SPEC after shipping and mark up. They currently don't offer a SPEC 3+. Call and ask for "Paul," see if he will have one made for you. If not, you can PM me and I will see what I can do.

Kurt