DX to HF... prepare to flame
#1
DX to HF... prepare to flame
Alright bros, here's the deal. 1990 EF Civic DX that runs like a wet dream.
Spare motor being rebuilt needs a transmission. Why not mate an HF transmission for better MPG's? (when current motor blows up, I can swap in a fresh set up)
HF trans are hard to find, found one on EBay. Transmission is from a wrecked 86 CRX HF.
Noob question- WILL it mount up in my 1990 EF?
OR will someone point me in the right direction to find out for myself
thanks guys!
Spare motor being rebuilt needs a transmission. Why not mate an HF transmission for better MPG's? (when current motor blows up, I can swap in a fresh set up)
HF trans are hard to find, found one on EBay. Transmission is from a wrecked 86 CRX HF.
Noob question- WILL it mount up in my 1990 EF?
OR will someone point me in the right direction to find out for myself
thanks guys!
#2
Honda-Tech Member
Re: DX to HF... prepare to flame
Yes, all 88-91 cable d series transmissions are interchangeable.
Edit: Not sure about 86 hf, but you might as well just get the 90' STD 4 spd for economy.
Edit: Not sure about 86 hf, but you might as well just get the 90' STD 4 spd for economy.
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Re: DX to HF... prepare to flame
I did basically the same thing in my 94 Civic CX. It didn't work out the way you would think. Longer gears by themselves don't automatically equate to better gas mileage. In my case the gear spacing dropped completely out of the power band with each shift. Combine that with where a DX generates max torque and where an HF generates max torque you will find yourself giving it more throttle to maintain the same speed essentially lugging the engine along.
#7
Re: DX to HF... prepare to flame
wow, im glad I asked. that will make sourcing parts much easier then.
Just so I understand gooder, can you go into more detail about how DX works, versus HF? If they are both powered by the same engine, why wouldn't the HF trans work?
Thanks again, guys!
Just so I understand gooder, can you go into more detail about how DX works, versus HF? If they are both powered by the same engine, why wouldn't the HF trans work?
Thanks again, guys!
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#10
Honda-Tech Member
Re: DX to HF... prepare to flame
I actually did mate an HF tranny to my DX engine just to see what would happen, and yes the gearing was WAY out of the power band and was just miserable to drive.
I ended up swapping the HF 4th and 5th gears into the DX tranny, and I noticed a 4-5 mpg gain while still feeling peppy at the same time.
I ended up swapping the HF 4th and 5th gears into the DX tranny, and I noticed a 4-5 mpg gain while still feeling peppy at the same time.
#11
Re: DX to HF... prepare to flame
DX and HF engines are NOT the same actually.
The engineers at Honda are pretty smart with all their degrees, experience and calculations. They usually try and match the transmission gearing to the engine output to keep the vehicle reasonable to drive. They do have to balance a lot of factors, economy, power output, reliability and making at it reasonable to drive.
If you want to transmission swap you are best sticking with the 89-91 transmissions since 88 has a one year spline difference on the input shaft. the 87 and back transmissions will require custom work to go in. If you have a 4 spd transmission a 5 speed from an SI or DX model would be a decent upgrade, however the best way to control fuel economy is through your right foot.
The engineers at Honda are pretty smart with all their degrees, experience and calculations. They usually try and match the transmission gearing to the engine output to keep the vehicle reasonable to drive. They do have to balance a lot of factors, economy, power output, reliability and making at it reasonable to drive.
If you want to transmission swap you are best sticking with the 89-91 transmissions since 88 has a one year spline difference on the input shaft. the 87 and back transmissions will require custom work to go in. If you have a 4 spd transmission a 5 speed from an SI or DX model would be a decent upgrade, however the best way to control fuel economy is through your right foot.
#12
Re: DX to HF... prepare to flame
this has been super helpful.
I had no idea how many differences there were between HF and DX
If i ever swap an engine, i will really have to do my research.
Thanks guys!
I had no idea how many differences there were between HF and DX
If i ever swap an engine, i will really have to do my research.
Thanks guys!
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freezerburnv2
Honda CRX / EF Civic (1988 - 1991)
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09-04-2005 04:16 AM