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Subbie Outback
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Discussion Starter #1
I've searched this forum and have been keeping up with the roadrace trans thread, but haven't found the answer I need.

We run a gravel stage rally car built from a 91 DX hatch with a D15B2 and a 91 CRX SI trans.

We want to build a new trans with a much closer gear set. For our uses, the SI trans has a decent 2/3, but 4th is too much of a stretch, with a big RPM drop. 5th is unusable as is 1st, other than getting to 2nd. if we could get a longer 1st and a shorter 4/5, that would really help. Something like this Quaife rally gear set for a Honda trans.

Gear Ratios

1st 2nd 3rd 4th 5th

2.462 1.813 1.500 1.250 1.045

The threads I've read talk about having 3 good gears (2-3-4 or 3-4-5), but we are looking for good gears. In this kind of racing, it's all about getting around the gravel corners and up to speed again. Top speed isn't as much a concern as limiting rpm drop between gears.

Using the case we have, could someone point me to a thread that lists the trans we need to be looking at for the gears we need (or just give us the info)? I can read gear charts to figure out the ratios, but I don't know what gearsf rom what trans we can use in our case.
 

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Brokedick Millionaire
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40,313 Posts
You are pretty limited of choice on 1st gear and second gear

3.083 MFactory
1.894 stock
1.565 MFactory 3rd
1.250/1.259 (modified stock 3rd gear)
1.000 MFactory 5th, slight clearancing of the case needed

Aquafina on here can help you with MFactory parts.

http://www.d-series.org/forums/whoopee-doo-racing/

Using OEM gears
3.250
1.650 (1-2 rpm drop SUCKS)
1.346
1.066 (modified 92-95 3rd)
.878
 

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Subbie Outback
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Discussion Starter #5 (Edited)
Thanks for your help.

You are pretty limited of choice on 1st gear and second gear

3.083 MFactory
1.894 stock
1.565 MFactory 3rd
1.250/1.259 (modified stock 3rd gear)
1.000 MFactory 5th, slight clearancing of the case needed

Aquafina on here can help you with MFactory parts.

Whoopee Doo Racing - D-series.org
These are the ratios I came up with looking at the info in the threads. Looks like 1st will be limited to a launch gear, but the rest (2-5) look usable. I was hoping there was a 1st or 2nd gear we could use for 1st that was closer to 2.5 in some uncommon trans.

Could we use the modified 92-95 3rd as the 5th gear? That would give us less of a rpm drop between 4 and 5 and make 5th more useful. We need a top speed of about 90-100, but spend most of our time between 30 and 70. We might need to change out the fd ratio to get there if the 1.066 5th won't do it. We are using the stock CRX SI fd. We run a 7500 rpm rev limit with 175/60 14 tires.
 

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Discussion Starter #6
What's the top speed you need?
About 90-100mph. We're hitting that in 4th now, but it takes a while to get there due to having to recover revs between gears. The straights are never long enough to get into 5th with the long gearing that's in the trans now. We'd like to top out in 5th between 90-100mph. That's scary fast on a gravel road with a bank on one side and a cliff on the other. :)
 

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SCCA F Prod CRX Si
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I hear ya. For what it's worth I hit right about 100 with a 4.9 FD on stock CRX Si gearing. With that and with a closer 2-3 you maybe able to have a 2-3-4 that works better.
 

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SCCA F Prod CRX Si
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Played with my calculator a bit. Same gearing as I am looking at but with a 4.9 FD would give nice drops and a top speed of 106 mph. But you would need a later box to fit the m-factory stuff. Otherwise I think a 2-3-4 box would be all you could do.

3rds can't be used as 5ths.
 

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Discussion Starter #9
But you would need a later box to fit the m-factory stuff.
Really? This is from the MFactory thread describing the close ratio gear set:

Applications are all 88-00 Civic transmissions. 88-95 transmissions require slight modification to the transmission case where 5th gear sits.

Looks like my case should work.
 

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Brokedick Millionaire
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40,313 Posts
Ian, what do you think I dropped in Freds EP case?

Which is for sale, not listed on here as it would be a pretty penny. Adding OEM 1.250 3rd and MFactory 5th would be needed....

"Quaife, 4.7FD, Gear-X 1st & 3rd gears"
 

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Brokedick Millionaire
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40,313 Posts
88-91 and 92-00 the 3-4 hub is flipped, which is only a minor issue. When flipping 3rd to 4th if you use the other generation, one less machining step needed, but still need to thin the CS 3rd to 4th gear by 1mm.

Unless Chris is hiding more accurate details :)
 

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1996 Civic Type DX
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I am. They'll stay hidden unless you want to buy one of my transmissions. :wink:

The MFactory gears work in the 88-00 case. The FD's are specific to cable or hydro. Replied to your message Henry.
 
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