swapping 5speed to Auto for race purposes only

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Buschi340

Buschi340

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me having stupid ideas again.
Just for some race Weekends i want to swap out my Toyota 5speed for an automatic tranny. And swap back afterwards hahahaha
Got a deal for my MT Semi's i don't use anymore to get a 727, 904 or 998 core to rebuild.. Which one is best in your eyes? 998 i don't know at all. 904 is not heavy but can it survive approx 400hp on Slicks on prepped tracks? 727 is strong but heavy.
what is the best adapter Flex plate to use?
everything else is more or less Standard. shifter, cables, hoses etc

what converter are you Auto guys running with a rear Ratio of 4:10 or smaller? Need to drive 150mls on own tires to the track...

regards from Germany,
Michael
 
You will do this once, and realize it's way too much work. And expensive. 904 trans is light, uses less horsepower, and can be built to easily handle 400 hp. The flexplate should be SFI certified, like a B&M. Also has to have the right balance for your engine. For a converter, you should contact a quality company like Dynamic converters. They will ask fo a lot of info before giving a recomendation. Good converters are not cheap. Driveshaft will probably be the wrong length. Slip yoke, cooling lines, trans cooler, shifter, etc. Good luck.
 
I run a 998 out of a 84 Diplomat. Lockup tranny with TCC circuit plugged, TA S800 ST 10" 3200, drive 50 miles to the track. Trans has low gear set and I've run 3.91 and current 4.10 gear. 60' 1.65 @2k launch average. 340/400hp
 
Only one flex plate available for 727/904, ATI. 904 can be built to handle big power, equals expensive. 727 is heavier and takes more power, but, spend virtually nothing to build(not being stupid horsepower). Looking at doing different cross members and driveshafts. I admire your tenacity, but, you might get sick of it.
 
what do you mean with getting sick of it?

well, seems it will be the TF998. The Buddy i am dealing with said its in best condition, takes easily up to 600HP, not so heavy. And i have a Buddy running the same into low 11 ET's.
I know it is a bit crazy but i really want to crack the 12 sec. :) And with the Manual tranny I have it is impossible without a power adder.
 
Buschi340 said:
what do you mean with getting sick of it?

well, seems it will be the TF998. The Buddy i am dealing with said its in best condition, takes easily up to 600HP, not so heavy. And i have a Buddy running the same into low 11 ET's.
I know it is a bit crazy but i really want to crack the 12 sec. :) And with the Manual tranny I have it is impossible without a power adder.
Click to expand...
What do you have for a motor and suspension package?
 
I meant switching transmissions all the time. Don't mean anything bad by it.
 
oh yes, thats probably true. time will tell. But great to have options on both from my own shelf or not ? And having a shop lift makes it somewhat easy.
 
stock 6.1 but carbed. will have a new cam in for next season. Springs in front are qa1 double adjustable coil overs, single adjustable ( still ) in the rear. stock leaf springs but mono leafs for next season.
 
How much time do you expect to shave with the automatic?
When you say crack the 12's what ET are you looking for? Is that into the 12's?
It seems to me it shouldn't take much for a 5.9 to get into the 12's.
Into the 11's is a lot harder.

In used to do that swap twice a year; spring and fall, 5 years in a row. 360HO in, in spring with an A833, and swapped out for a 318/something else, in fall. That 68 Barracuda was my DD. Boy I was glad when I got a better paying job and could afford a second car. I was 47 when I started thatchit.
 
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408 swinger said:
Only one flex plate available for 727/904, ATI. 904 can be built to handle big power, equals expensive. 727 is heavier and takes more power, but, spend virtually nothing to build(not being stupid horsepower). Looking at doing different cross members and driveshafts. I admire your tenacity, but, you might get sick of it.
Click to expand...
There are several flex plates available, based on the engine used. Mopar has many different engine balances for both big block, small block, and probably the gen 3 Hemi
 
oh, crack the 12s i mean 11.99. My best ET was 12.718 with this Toyota 5 Speed. I can go into the 11s just because of the shifting itself... engine is a 6.1 with a 750 Holley
 
furyus2 said:
There are several flex plates available, based on the engine used. Mopar has many different engine balances for both big block, small block, and probably the gen 3 Hemi
Click to expand...
Only speaking of gen 3.
 
With SS suspension it only takes a P/W of about .107 to "CRACK" the 12s and get an 11.99. With you and the Swinger weighing a max of 3400, that would be 367 HP.

If you have 400hp and 3400 pounds , that would be a PW of .1176 which is an 11.7 potential. At 12.72 you are dead on for a 1 second loss in the suspension.
In which case, to get an 11.99 with that suspension, you might need 455hp
Which one to fix I guess is up to you.
 
hm, yes thats indeed an issue when seeing my runs with the butt of the car hopping up and down at start and at every single shift. I use caltracs on stock leaf springs and single adustable qa1 Shocks. ( coil over in the front ). I can't Keep my cars butt up ( or down - butt mopars butts doesn't stay down )
 
P/W is Power to Weight Ratio . I used 400/3400=.1176
MaMopar compiled a chart back in the 60s which translates P/Ws for 9 to 16 second SuperStock cars. They say it's pretty accurate, for SuperStockers.
I use it on streeters by adding between .5 and 1.0 second for street suspension and street gears, and street tires, etc.
And I use it backwards to calculate power needed to achieve an ET with street suspension. It's not always accurate when used that way, but it gives you an idea of what to expect from a given combo, with in +/- about a half second.

Your avatar looks like a 70/71 Swinger; how did you get it up to 3660?
Mine scaled 3330 back in 1971, with 18 year old 130 pound me in it, so 3200 for the car alone . That was a 340-4speed 8.75 with P/S and P/B, stock Rallys and E70-14s,lol, and a bithin 8-track stereo, cranking out the Rolling Stones.
What? Subwoofer? No that was before them, Just two 6x9 triaxles, and a pair of 5s in the doors, state of the art in 74........

If your car truley scales that heavy, then your P/W would be 400/3660 =.1093 and a SuperStocker might go 11.9 with that. Your Caltracks will help you with that, and so would the 4.10s and M/Ts.
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My car was 3650 and went 12.9/106 with a 4 speed, 3.55s and street tires. The engine was a 367 with OOTB Eddies and a [email protected] cam . The 106 says P/W was .09236 and a SS suspension shoulda gone about 12.5. So that combo was not far off the mark.
BTW, that P/W of .09236 translates to 339hp
 
my Speed was 111 mph btw.
3660 is the weight the local dumpsite measured. Maybe they show too much to rip off customers hahahaha..

i probably will get mono leafs and 2 way adjustable qa1 in text few months. Buddy is converting to 4 link. Out of a b Body but shortened to a Body to get his but lower
 
there you go; the 111 says WP of 9.15, so at 3660 that would be 400 on the nose and with SS suspension should be good for about a tic under 12.00.... at 12.72 you are about right for street suspension. Maybe a hair slow with slicks, Caltracs and the proper trapping gears. So you could be right about the scales, being heavy.
 
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