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Thread: Transmission: rebuild or 5speed swap???
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remydrm
Revvin Up
Posts: 92
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posted August 09, 2012 04:16 PM |
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Transmission: rebuild or 5speed swap???
I'm about to drop in a new motor and was wondering what people thought would be the best way to go with regards to the transmission.
Should I keep the 4 speed and having it refreshed for about $500?
Should I install a RX7 5 speed? If so, which generation? How much modification would be required? And most importantly, can I do this without notching my floor/tunnel?
Thanks!!!
Massi
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Brad
Rotorhead
Posts: 1672
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posted August 09, 2012 10:22 PM |
 Edited By: Brad on 9 Aug 2012 22:27 |
I'd be impressed if you can find tranny parts for a old school ribcase 4 speed. MAZDA had next to nothing left in stock years ago but there could be aftermarket kits still sitting on shelves.
If you do want a more modern 5 speed that's plug and play w/o cutting the floor the 79-80 is it. You can get rebuild kits off eBay! BUT it has the weaker synchros so no power shifting. I"ve done drag race launches using that generation of tranny and it works like a champ. BUT you either need to fab an adaptor plate for trans to trans crossmember or if you have time on your hands notch the stock trans crossmember and redrill the trans mount. I've done both, getting the trans angle right is a lot of fun as it reduces vibrations, noise and increases driveline life.
OH and if you use a 81-85 bellhousing & gearbox you can use a Miata tailhousing that has a built in short throws but you have to cut the floor a few inches as the shifter is further back..You can also use Mazda 626 internals which have semi-close ratios for less rpm drops on shifts and a real short 5th gear to eat your gas money.
People also use a 2nd gen trans and move the shifter forward, Scott (SPARKY) has done this and can chime in.
You won't need to cut the trans TUNNEL at all if you use a mazda box.
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remydrm
Revvin Up
Posts: 92
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posted August 10, 2012 12:37 PM |
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Thanks for the info Brad. I'm not sure what to do. When I bought the truck, I never got a chance to drive it. I was told the transmission is fine but I'd like to address it while it's out of the car and loose.
I've got a GSL-SE trans with Miata gears in my EP car. That feels great and it was a cheap way to upgrade from stock.
Hopefully Sparky will chime in... I'd really like to avoid cutting the floor since it just got painted.
massi
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Brad
Rotorhead
Posts: 1672
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posted August 10, 2012 03:13 PM |
Edited By: Brad on 10 Aug 2012 15:15
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you can fill it with fluid and go thru the gears with it on the shop floor. and turn the input shaft by hand listen for bearing noise.
what region do you race EP in? and 1st or 2nd gen? got any pics?
Here is my track car which also has a 626 box. It is parked mostly. http://rides.webshots.com/album/37109845iDWtpz
the 79-80 5 speed is an easy way to go; don't need to cut the floor.
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remydrm
Revvin Up
Posts: 92
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posted August 13, 2012 04:35 PM |
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Hey Brad,
I'm in the N.Cal region but haven't been participating in the last couple years. Had a couple engine failures and then just got busy with other projects... like this REPU.
My FB is pretty well sorted and all that's really left is the bodywork. I've been holding out since I've got a couple other projects going and the car wouldn't see any real race time for another year or so.
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Jeff20B
Moderator
Posts: 661
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posted August 14, 2012 11:07 AM |
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Don't cut the floor. Instead, move the shifter forward.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7
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