i have a d15b vtec and a unknown transmission i have driven the car around town like 1000 miles or more but the other day i got on the highway and was cruising at like 80 the rpm gauge read 4 thousand rpm? im pretty sure i have a si transmission. is this normal for a si trans and a d15b vtec? i couldnt drive on the highway for too long cause the car sounded so loud..i want a better geared tranny any suggestions?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueCrxNC &raquo;</TD></TR><TR><TD CLASS="quote">4K @ 80 mph does sound like an Si tranny. Should be more like 3800 but that all depends on your tire size.</TD></TR></TABLE>


That's technically true but tire size wouldn't affect his speedometer readings.

The speedo is driven off the pumpkin so it has no idea what size tires you are running.

If you are running 13 inch rims at (using your example) 3800 your speedo will read 80mph and using monster truck tires 3800rpm will read 80mph.

Now if you are checking your speed with a radar gun then yes you'll see a difference with tire sizes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueCrxNC &raquo;</TD></TR><TR><TD CLASS="quote">
We all make mistakes. I'm not trying to jump on your case or anything but please make sure you know exactly what you are talking about before stating it as fact.
Modified by BlueCrxNC at 10:39 PM 10/10/2006</TD></TR></TABLE>
Reading Comprehension... F

Tire size will affect ACUTAL SPEED
Tire size WILL NOT affect speedometer reading unless it is corrected...
Therefore unless he took his car and had his spedometer corrected for diferent diameter tires then the speedo to tach relationship will remain unchanged.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueCrxNC &raquo;</TD></TR><TR><TD CLASS="quote">We all make mistakes. I'm not trying to jump on your case or anything but please make sure you know exactly what you are talking about before stating it as fact.</TD></TR></TABLE>
He is right, and knows exactly what he is talking about (though he could have phrased/explained it a bit better). Tire size absolutely does not affect speedometer vs. tachometer reading ratios; tire size only affects the actual ground speed vs. indicated speed ratio. The speedometer is geared off the differential, so it only counts the revs of the diff, and calculates speed by the circumference of the stock tire size.


Modified by Targa250R at 7:22 PM 10/11/2006

 

well that was just one big argument i want to know if maybe when i take it out i can swap 5th gear and still have 1st through 4th stay the same? if so what tranny has a better 5th gear that i can use because that si tranny stinks as far as 5th gear..i like taking long trips and 4k at 80 miles an hour is going to blow through some gas!!!

 

No it's not, the car is going to get 40+ on the highway. Honda designed it that way for a reason, it's not bad for anything.

 

at 4k the car is going to get nowhere near 40 mpg in fact im sure at 55 in 5th gear it wouldnt get nowhere near 40 mpg or at any speed in any gear for that matter..hybrid cars have a hard time getting 40mpg

 

You can switch to a DX 5th gear or if you really need a long gear....than HF may suit you fine if you can find a set. The old 88-91 stuff is becoming extinct and hard to find! Good luck!

 

if i change the 5th gear will everything still be the same? as far as 1st through 4th? also i have seen a d series hydraulic transmission that has a lsd unit, if i buy the tranny could i just put all the guts into my d series? the tranny im speaking about is from a 92 95 civic which makes it hydraulic..i can do swaps wiring troubleshooting anything but transmissions thanks for the help

 

yeah you can interchange most of the gears, my crx has zc gears 1-4, HF 5th gear, i get about 44mpg on average on the interstate at 3100rpm. I can actually have conversations with the windows down, nice and quiet. I have the EX final drive right now which is 4.05 but I will soon be swapping that out for an ATS which is 4.73 along with a mugen LSD. Should be able to swap any of the D-series interchangeably.

 

thanks for the intelligent response im definetly going to save up and tear my tranny down and put different gears in it, are the zc gears better? 1st through 4th

 

i think the first gears are the same on all crx's, but 2-4 are really short, then the extra long 5th gear from the HF, there's a bunch of write ups on honda tech on good gear combinations for D-series.

 

Apologies to JohnnieChimpo. I was online late and OBVIOUSLY wasn't thinking properly. Again, Sorry.

That aside, <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GearSpeedEF7 &raquo;</TD></TR><TR><TD CLASS="quote">You can switch to a DX 5th gear or if you really need a long gear....</TD></TR></TABLE> The DX and Si CRX share the exact same gears 1-5. The only difference is the Final drive Si:4.25 DX:3.88

Another website with more transmission info http://www.d-series.org/forums...19200


Modified by BlueCrxNC at 7:24 PM 10/11/2006