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Thread: Rear Gear Ratio
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2wankel
Hauling
Posts: 133
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posted September 13, 2007 04:02 PM |
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Rear Gear Ratio
Did all manual REPU's come with 4.62's?
thanks
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VMRC Website
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Hunter
Hauling
Posts: 178
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posted September 13, 2007 04:29 PM |
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diff ratios
74 AT 4.375
76 MT 4.375
76 AT 4.111
I don't have a TDB for 75 and 77
anyone ?
Bruce Toski
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sparky
Redlining
Posts: 299
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posted September 13, 2007 08:03 PM |
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My '77 has a 3.90, Just did the torsen upgrade. Ring had 39 and pinion gear had 10 teeth.
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Dryenko
1st Gear
Posts: 38
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posted September 14, 2007 05:05 AM |
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My 1975 REPU AT truck came with a 4.11 rearend ratio.
I converted truck to a rib case Cosmo 5 sped.
It was then geared to tall for a 4.11
Changed to 4.37 and it worked great with a warmed over 13B.
Recently installed a rebuilt 80 RX7 5 speed trans and a 4.62 rear end ratio.
Works pretty good, but 5th gear is too tall to use except for 70 MPH+ highway cruising empty.
I have 215/60 x 15 tires, for reference.
Will most likely will install a good RX4 5 speed trans and keep the 4.62, that way 5th will be more useable.
YMMV
Bob C
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Klaus44
Redlining
Posts: 365
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posted September 14, 2007 10:32 AM |
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I think I posted these in another thread...
...but, here goes again:
74 Manual -- 4.625 Rearend
74 Auto. -- 4.375
75 Manual -- 4.375
75 Auto. -- 4.111
76 Manual -- 4.111 (first year 5-spd. offered...)
77 Manual -- 3.900 (5-speed)
(Mind you, these are *not* final drive ratio's!)
Above taken from "US spec. Mazda driveline ratio's", http://mrmazda.members.atlantic.net/tranchrt.txt , printed out 3/31/02.
...and depending on tire brand, etc., a 205/50/15 approximates the stock Bridgestone 7.35-14 outer diameter pretty well...
;) --K.
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2wankel
Hauling
Posts: 133
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posted September 14, 2007 11:16 AM |
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thanks Klaus44
Is there a considerable difference in acceleration/pulling power between 4.625 and 4.375?
thanks again
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VMRC Website
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Klaus44
Redlining
Posts: 365
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posted September 14, 2007 12:05 PM |
Edited By: Klaus44 on 14 Sep 2007 12:06
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I'm sure...
...there's some -- all depends on your transmission gears, wheel/tire choices, engine, and driving style...
I haven't compared apples to apples, so to speak... but, the 4.625 rearend makes 1st gear *really* low, when running a 1st-gen rx-7 5-speed...
...and 2nd & 3rd... really RIP! ;)
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Brad
Rotorhead
Posts: 1672
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posted September 14, 2007 04:22 PM |
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yeah
quote:
thanks Klaus44
Is there a considerable difference in acceleration/pulling power between 4.625 and 4.375?
thanks again
you'll notice it.
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2wankel
Hauling
Posts: 133
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posted September 15, 2007 07:01 AM |
Edited By: 2wankel on 15 Sep 2007 07:04
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What rear end gear ratio do you recommend for a full bridgeport? From the info posted here I have a 4.3 rear. The truck has a 4-speed.
While we are at, what about a good tranny rear end combo for a bridge?
thanks I appreciate you comments.
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VMRC Website
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Brad
Rotorhead
Posts: 1672
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posted September 15, 2007 12:12 PM |
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quote:
What rear end gear ratio do you recommend for a full bridgeport? From the info posted here I have a 4.3 rear. The truck has a 4-speed.
While we are at, what about a good tranny rear end combo for a bridge?
thanks I appreciate you comments.
The full bridgeport doesn't wake up until > 4000rpms and really has a kick around 8000rpms. that said you want short gears to get you into it's powerband quicker and a closer ratio box to keep you there.
4.625 and a miata 5 speed box is the cheapest bet. All the rx7 boxes are wide ratio including the infamous T][ that people like to put behind their race ported motors. Miata box is semi-close ratio and can fit in a 1st gen case with a 1st gen bellhousing. Put the miata tailhousing on the end for built in short shifting and you're all set. Only need to move the shifter hole a few inches. 2nd gen miata box also has dual helical gears for better shifting.
Brad
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-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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2wankel
Hauling
Posts: 133
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posted September 16, 2007 07:13 PM |
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Thanks Brad, great information. Are there step by step pictures of the miata swap into the rx7 box?
thanks again
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VMRC Website
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