10 replies to this topic

[TheBaron862]

i have a brown top zc in my 86 si and i don't like how high the rpms have to be for me to drive on the highway. i do a lot of highway driving and would like to put something that will give me better gas mileage and keep the rpms lower. will an hf or dx 5th gear fit the cg transmission? if so, does it have to be from a certain year crx? are there any other 5ths that will fit this transmission? thanks for your help.
                                   --Jeff

[dacollier1]

I beleive that the shaft diameter is larger on the CG than any of the USDM civic trans, so none will fit.   Your choices are the 5th gear from a 86-87 or 88-89 integra (which is a bit lower numerically than the 86-87).  I also think I've seen that the 1984 Accord 5th gear will work, and it's lower than the integra one.   You could just swap the integra trans in completely, but you can't do that with the Accord.

[boman]

I also remember vaguely reading that the 5th gear from a
Prelude fits.  But nobody could verify this.  It would be
interesting to figure this out.

JAKOB

[87wagon]

I have an 87 Prelude 5th gear set in my 87 Integra tranny (CG).  It's a .757 ratio as I remember, a useful difference from the .85 or so of the Integra 5th.  Accord 5th gear sets from that general period will also fit--they're .694.

[87wagon]

Oh, I meant to add, a guy here in Portland (OR) dismantles transmissions and sold me the 5th gear set for $50.

[boman]

I have an 87 Prelude 5th gear set in my 87 Integra tranny (CG).  It's a .757 ratio as I remember, a useful difference from the .85 or so of the Integra 5th.  Accord 5th gear sets from that general period will also fit--they're .694.

BINGO!!!  Thank you so much for posting that! So where is
your rpms at 120kms (75mph)?

JAKOB

[r4adkshn]

yeah, what's the results? inquiring minds want to know

[87wagon]

Sorry to be slow in responding--the engine and transmission are in the process of being installed in the 87 wagon, which explains the delay and explains why I can't tell you on the road rpms at 75 mph. But, based on the 3100 rpm at 70 mph I had with the stock engine and tranny, I calculate about 3500 rpm at 75 w/ the .757 5th gear (stock tires and wheels). If that's still too high, you might try the Accord 5th (.694), but you're starting to get a big gap from 4th to 5th.

[RexKrazy]

based on the 3100 rpm at 70 mph I had with the stock engine and tranny, I calculate about 3500 rpm at 75 w/ the .757 5th gear

uhhh....i think you got yo numbers a bit crossed up...i hope. it looks like rpms actually RAISED (theoretically) w/ the new gear...

[87wagon]

When I said "stock" engine and tranny, I was referring to the engine and tranny that's in the car now (to be pulled this week). That's the carbed 87 Civic engine (EW, I think) and tranny (GW, I think). That transmission has a .718 5th and a 4.25 final drive. The Integra tranny has a 4.25 final drive and now (after the installation of the Prelude 5th gears) has a .757 5th. To calculate rpms at 75 I started w/ 3100 at 70, multiplied by 75/70 to adjust for the different speed, and multiplied by .757/.718 to adjust for the different 5th gear ratios. No adjustment necessary for the final drives.

3500 rpm is higher than the 87 Civic tranny would give, but lower than the stock Integra tranny (whose 5th is about .85) would give. I calculate that would be about 3100 times .75/70 times .85/.718 = 3932 rpm.

[RexKrazy]

i really dont have time to think about calculating....but i really feel like simethin is wrong there.