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Index > Engine/Drivetrain > Thread: any advice for converting a repu to automatic
Thread: any advice for converting a repu to automatic
rotarypwrd


Revvin Up
Posts: 55
posted September 13, 2002 02:23 PM

any advice for converting a repu to automatic

it's for the mrs.. planning on putting an 89-91 motor w/ fuel infection conversion, what's my best option for an auto trans. and path of least resistance to do it.

74 rx4 wagon auto tranny, 89-91 rx7 auto tranny, or 1st gen rx7 auto tranny? and will that auto tranny hold the xtra power, may street port? rotarypwrd

       
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Uncle-Jim


Revvin Up
Posts: 64
posted September 13, 2002 02:44 PM

I am told that the Jatco 3 speeds were almost unbreakable. I'd probably try to find one in an early Rx-? and install. Be sure to check Felix Miata's website for things to watch for.
http://members.ij.net/mrmazda/main.html

Check with some Rotary rebuilders, most people were coverting to 5speeds, and some auto's might be had real cheap. If I get around to rebuilding my Cosmo, I'd give you the tranny, but I'm still some time away from that project yet.
You could also try to mate up a GM turbo 350 or 700RL. Those are good units, and lots of parts available.





____________
Uncle Jim
72 Rx-2 Show Car; '77 REPU (250K & goin' strong) 2 - '76 Cosmo's

       
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Klaus43


Rotorhead
Posts: 1259
posted September 13, 2002 04:34 PM
Edited By: klaus42 on 13 Sep 2002 16:35

Don't know about the 89-91 motor, but...

...the '74 rx-4 unit is likely identical to that offered in the REPU. To me this means that it will fit with no cutting, just likely need a crossmember-maybe even not! Unbreakable, perhaps--but these tranny's have a reputation for going 40-something K miles before something needs done... so I guess the moral is : maintenance! Newer transmissions might require some modification of the cab for shifter location; I'd avoid this...however, the 1st-gen rx-7 auto. w./overdrive might be a desirable unit to have...and not require such cutting.
By the way, why not track down a REPU that was originally an automatic, and restore that for your wife, instead? That way you could still enjoy shifting!
P.S.--Power of a streetport should be no problem. :)

       
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Jeff20B


Moderator
Posts: 661
posted September 13, 2002 08:32 PM

I've got a Cosmo with an auto that I just got running, well, driving that is (it's been running more or less since '98). I am in the middle of purchasing a pedal assembly from a manual car for the day I decide to go with a 5 speed. I've read here and there that the old Jatco trannies can take at least 400HP, but 600HP would probably break it. Not sure about the torque, but a turbo 13B's torque won't break it. Check out http://www.geocities.com/mazdarx5/ to see what I'm talking about. Yeah, just maintain it properly and it'll easily handle a streetport. I plan to run mine with a 20B eventually.

       
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rotarypwrd


Revvin Up
Posts: 55
posted September 13, 2002 09:03 PM

sorry for the lack of terminology regarding auto trans. names..........but wqhat is a 3spd jatco trans.? is it the one in a 74 rx4 wagon stock, or is this custom? don't need a racer autotrans, just a strong enough one to handle about 250hp and 230 torque, give or take. if custom how much would this cost me?

lastly, thinking about a limited slip for the rear, what will work fr the easiest bolt-on job........1st gen gsl, gsl-se rear lmtd slip, or 89-91 gtu, turbo rear?

really appreciate all the input and help rotary enthusiasts!!!!!!you're advice and counsel is invaluable to me. helping me eliminate trial n error and not making some previously made mistakes twice. hope te meet n greet n thank some of you personally at seven stock.

rotarypwrd, tomas

       
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Tom93R1


Redlining
Posts: 458
posted September 13, 2002 09:56 PM

I don't know much about the 1st gen rx7 but I know the 2nd gen rear is independent. That would be a big project to swap. I Think your best bet would be to find some other truck or car with a solid posi rear end and figure out how to adapt it.
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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rtrypwr


Hauling
Posts: 115
posted September 13, 2002 10:29 PM

limited slip

no mazda truck rear end came with a limited slip[ iv'e been told]also remember, 6 lug and same pattern. i have a friend that can make a later b2000 or 2200 into a limited slip. i'm going to the wreckers this weekend to find one. different years and models have different gear ratio's also when i get it done , i'll let you guys know what modification's had to be done,and what it will cost to have him do it.

       
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rtrypwr


Hauling
Posts: 115
posted September 13, 2002 10:57 PM

89-91 conversion

89-91 is not that easy, at least with the stock ecu,and making it smog legal.oil metering is tied in with the ecu. you don't have the stock one,or not functioning properly ,ecu locks the ignition etc[no power]gsl-se front cover has to be modified to accept it.then you've got the chech engine light that 88- does not have. any codes no smog! B.A.R wants EVERYTHING that was in that rx-7 in your truck ,including the air box. visual as well as functional check on EVERYTHING. you got my # thomas call before you make any decisions.

       
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rtrypwr


Hauling
Posts: 115
posted September 13, 2002 11:02 PM

p.s.

and if you do this swap, i'll tell ya how i adapted the complete 91 A/C into the truck. that is if you want your wife to be comfortable while she's driving it.

       
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rotarypwrd


Revvin Up
Posts: 55
posted September 14, 2002 12:11 AM

rtrypwr, thanks for the insightful info. I'll be in touch, got some serious questions. And like you indirectly stated, and I agree, know what you're getting into( blood,sweat, tears, time, n money) b4 you get into it.

anyone else on tips for the autotrans. to this conversion?

       
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repuguru


Redlining
Posts: 319
posted September 14, 2002 03:15 PM

Here is what I am going to have to do in order to convert my REPU over to automatic.
F and R auto 13b counterweights
Auto flexplate
Auto tranny assembly w linkage & converter
Automatic brake pedal.

The variable for me is going to be the location of the tranny crossmember. At this time I plan on using the 84-85 Auto w/overdrive from a 7.
I am still pondering whether to hang a cooler for the tranny externally aft of the oil cooler or have the radiator integrated tranny cooler tanks the way it is stock.
The only thing I have not checked is to see if the drive shaft will be proper length. Since I don't know the length of the 7 tranny yet.
Its not anything I can't have modified. But screw together would be ideal.

One thing I am going to do is have the stall speed on my converter changed to a higher stall. Say about 2200 somehere? It will totally change the way it takes off from a dead stop or towing.

       
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Jeff20B


Moderator
Posts: 661
posted September 14, 2002 05:07 PM

Please let me know how to change it, because my Cosmo is slow from a stop, then picks up at higher RPM. This may not be an issue with a 20B, but I'm still curious on how to do it. The valve body too.

Oh, and Jatco is th ename of the auto that came stock in the old rotaries. Not sure about 1st gen 7s and later.

       
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rotarypwrd


Revvin Up
Posts: 55
posted September 15, 2002 01:10 AM

thanks jeff20b for the definition of jatco auto trans.

anybody? will the auto trans.(jatco) from a 74 rx4 13b wagon be a straight swap for my wife's repu? if not, what's involved for this manual to auto swap? thanx in advance

       
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Klaus43


Rotorhead
Posts: 1259
posted September 15, 2002 09:17 AM

I'm not 100% certain...

...but I believe it'd be a straight swap. Same year, same running gear, pretty much. Like the 'guru said, tho, those F&R counterweights must not be forgot. Far as LSD goes, rearend in REPU's different from all other rotaries...fattest axles, for one. Wagon next closest, BUT... I'd get an experienced Mazda pro. to swap in/fab a LSD unit into the stock REPU rearend...was once told it could be done for around $400...
Why not teach your wife to drive a stick? Just don't start her out in the REPU! (Could always be essential knowledge in case of an emergency, at the very least...) Who knows, she might come to enjoy shifting! :)

       
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repuguru


Redlining
Posts: 319
posted September 15, 2002 08:01 PM

It is as close to a swap as you probably will find. The drive shaft is the only thing I am uncertain of?

Let me see if my manual shows any difference in drive shafts. Better yet, what is the part number of the different REPU driveshaft, if there is one?

       
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rotarypwrd


Revvin Up
Posts: 55
posted September 16, 2002 08:52 AM

thanks repuguru,

get back to me asap about the driveshaft fitting I only have a day left to decide to pickup this 74 rx4 wagon's autotrans. for the repu. just want to make sure it's a straight swap b4 i buy. picked up my wife's repu (greenmachine) yesterday! yeah! mission accomplished.......and now the project, I'll try to have it running for seven stock.

       
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Klaus43


Rotorhead
Posts: 1259
posted September 16, 2002 11:01 AM

So, how complete/straight is this

'74 rx4 wagon... and where is it, and is it for sale, all or part?

       
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rotarypwrd


Revvin Up
Posts: 55
posted September 16, 2002 02:05 PM

klaus42 emailed you

       
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