Has anyone ever coupled a 3.4 dohc to a factory 85-86 4 speed? The even spacing of the gears seems like it would work really well the 7k red line of the engine.
------------------ Honestly, What is a "stock" Fiero?
I've seen it mated to the Isuzu 5 speed. I don't think you'd want that 4 speed if you intend to drive it on the highway, though. The 84 econo 4 speed will give the lowest highway RPM. The 84 performance 4 speed will have the best acceleration. The 85-86 4 speed is not the best for either one. The 5 speeds are both better for accelration and highway RPM than the 85-86 4 speed is.
I assume you mean a stick (I can never tell these things). I had a dohc mated to an issuzi 5 speed, 70 mph = 2400 rpm, put you foot down, even at 70 and it just went! Only down side was the spacing of 1st to 2nd was too big for my liking. I could be doing 35 in first, change to 2nd and by the time I got it in gear the revs had dropped way off but otherwise it was a great fit.
I currently have an 85 v6 with a 4 speed stick, 70 mph = 3000 rpm = way too busy (ie noisy) on the highway for any length of time but around town I would think it would be ok with dohc because of the better spacing of the rations and no oportunity to go that fast.
------------------ Anything I might say is probably worth what you paid for it, so treat it accordingly!
Why? If I may be as so bold. My 4 speed is decent for highway on the 2.8 I manage between 24-27 highway mpg. Also I want acceleration over economy.
The 85-86 4 speed is not the best for either acceleration, or economy. It's a middle of the road trans. The Getrag 5 speed is probably the best of the stock Fiero manual transmissions for what you want.
The 85-86 4 speed is not the best for either acceleration, or economy. It's a middle of the road trans. The Getrag 5 speed is probably the best of the stock Fiero manual transmissions for what you want.
The 85-86 unit is the strongest of the 4 speeds due to extra reinforcement of the case. I don't think the 4 cylinder case is a good idea to use with an uprated engine.
The 85-86 unit is the strongest of the 4 speeds due to extra reinforcement of the case. I don't think the 4 cylinder case is a good idea to use with an uprated engine.
Sure. I don't think any of the stock Fiero transmissions are rated to handle the more powerful engines that people are swapping in. Is the 85-86 4 speed stronger than the Getrag though? Unless one really wants to stick with the 4 speed, the Getrag might be a better option, for both acceleration and highway cruising.
Though if one wants to hop out of the simple bolt-in realm, the F23 is probably an even better option.
Sure. I don't think any of the stock Fiero transmissions are rated to handle the more powerful engines that people are swapping in. Is the 85-86 4 speed stronger than the Getrag though? Unless one really wants to stick with the 4 speed, the Getrag might be a better option, for both acceleration and highway cruising.
Though if one wants to hop out of the simple bolt-in realm, the F23 is probably an even better option.
Maybe OP *HAS* a 4 speed and would have to spend more money on a different trans...
Originally posted by Will: Maybe OP *HAS* a 4 speed and would have to spend more money on a different trans...
Then OP can use it if he wants. I was just providing the information on which ratios in the stock Fiero manual transmissions match up best with acceleration and how the 85-86 4 speed compares to them.
I never said he couldn't bolt it up. I don't know of any swap that has used that trans with the DOHC (which is what he asked), but there's no reason it wouldn't work. I do know the Isuzu and Getrage have been used, and they are better matches for the engine.
Thank you dobey, I appreciate the input. I haven't a ton of money for this swap, I can get an engine fairly cheaply, was just wondering if / how well the unit would drive out without swapping to a 5 speed. I like the idea of it, but that adds a considerable amount to the cost of the swap
The Getrag is obviously the best option, but IMO the Muncie 4-speed should work just fine behind a 3.4 DOHC. It's biggest flaw is, of course, highway cruising RPM. If that doesn't bother you with the stock 2.8 V6, it probably won't bother you much more with the 3.4 DOHC except for a possibly louder exhaust note (depending on how you build your exhaust system).
I have a 3.4 DOHC mated to an Isuzu. While highway cruising RPM is great, the very long second gear leaves a lot to be desired. I have acquired a Getrag 282 that will be going in later this year.
Thank you dobey, I appreciate the input. I haven't a ton of money for this swap, I can get an engine fairly cheaply, was just wondering if / how well the unit would drive out without swapping to a 5 speed. I like the idea of it, but that adds a considerable amount to the cost of the swap
The stock 4 speed should be fine. Depending on how your current clutch looks, you might want to replace it while doing the swap. With the DOHC you'll get almost 3000 RPM more usefulness out of each gear compared to the 2.8, though you might end up rowing through the gears faster than with the 2.8, because the 3.4 makes a bit more power.
Depending on the year the ECM needs a clutch switch input. Also some years they didn't mate the DOHC with a MT so you can't get an ECM factory programmed for the MT.
