I've had a 1989 CRX HF transmission in my 1991 Civic Wagon for about two weeks now. It's a direct swap. Based on measured rolling circumference of my 185/65-14" tires, I'm now turning 1800 RPM at 60 MPH. That's a welcome change from the 2800 RPM the engine used to spin. 2000 RPM now gives me 65 MPH instead of only 43 MPH. My new 3rd gear is slightly taller than my old 5th gear!
Other than first gear, every ratio is a lower numerical ratio. If you think a 3.52 Metro/Swift final drive is tall, try a 2.95! The 88-91 2WD Wagons came with a 4.058 final drive.
First gear is now halfway between the old 1st and 2nd gears. Not as bad as it sounds. But it does take more slipping of the clutch, especially on hills. I ordered a new Exedy/Daikin clutch disc before pulling the old trans. Not surprisingly, my 198k mile clutch was down to the rivets on the pressure plate side. I reused my old pressure plate and the throwout bearing that came with the HF trans. I'm sure both will outlast the rusty body.
The HF came with smaller tires than the Wagon. Which means the speedo gear is different. NY rust and corrosion prohibits me from swapping the speedo gears, so the speedometer and odometer are now off by 5%. That's based on the sizes of the speedo gears and GPS-verified. So I'm adding 5% to my miles for MPG calculations. 165/65-14" Insight tires would fix this if I could find them used.
Coasting in neutral isn't much different than coasting in 5th gear now!
I have Mobil 1 0w-20 in the trans right now. It shifted slightly better with my old Honda OEM fluid in there, but I'm not about to drain $20 worth of oil.
I recently drove out to Ohio for GeoPalooza (yes, in a Honda) and drove the speed limit with almost no hypermiling. Average speed was 54 MPH. Removing the first 100 or so miles from that tank that were hypermiled, I got something like 44 MPG. That's a pretty good improvement from the 37 MPG this car used to get at those speeds. I'm guessing the trans swap is a big part of that. I'm not expecting much, if any, improvement while hypermiling at low speeds. I did the swap to reduce the penalty of higher speeds.
I've noticed two issues with the trans. One is a growl in 1st gear if I let off the throttle. The other is a leaking shifter seal. Does anybody know if that seal is replaceable from the outside? I don't see anything about the seal in my factory manual.
I think the total cost was around $150. I'll probably never make that back before the car rots away, but I'll still have the trans.
Do not do this swap if you drive mostly in the city! I'm not even sure if I'd want this trans in an HF in the city. But it's amazing on an open road, even if I end up keeping it in 4th gear at my slower speeds.
Here are the overall ratios (gear ratios multiplied by final drive):
And the old clutch:
And with the old trans out:
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