I've seen a lot of questions asking which is better the getrag or the isuzu for the v6, but I don't recall seeing too much about a preference for a muncie 4 speed vs. an isuzu 5 speed for the V6.

If you had to choose between the stock four speed or the isuzu 5 speed (this v6 doesn't have either at the moment) which would you choose?

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84 Fiero with a 2.8 V6, Isuzu 5-speed, Performance Sound, Sprint Exhaust Manifols and a real pretty interior. :D

5 spd. Better gas mileage for one thing. The Muncie is a good tranny, but fairly weakly designed--from all I've read here. I have the 4 spd behind a duke and its fine for that, but I wouldn't want to put a LOT of power in front of it. Even with just the 4 cyl, I always feel like I still aren't in the highest gear when I'm already in 4th. Maybe it's different with the v6, but that's my impression with the duke and Muncie combo.

For performance I would go with the 4spd, but its all personal preference...

It all depends on what 4 speed you get. There are 3 that came with the fiero. In 84 there were the performance and econo trannies, the econo being the Rarer of the 2. And then the 85-86 v6 4spds. The 84 trannies' cases are weaker since, but the v6 4spds have additional webbing on the outside that pretty much solved the weakness concerns. The 84 performance trans. is pretty common but it is VERY low geared (4.10) while the econo trans. has 3.32 gears. The v6 trans has 3.65 gears. The econo trannies are pretty hard to come by and are very saught after buy the v8 crowd (Im one of those people searching for one.) One of the main problems with the v6 4spd that I know of is that the 3rd gear synchro/ blocker ring goes out on them. But All the 4 speeds are easy to dissassemble and repair. One cool thing about the 4spds is you can take the gears out of say either of the 84 trannies and put them in a v6 tranny case and you've got the different gears with the added strength of the newer case. I havent ever driven in a car with either 84 tranny, but Ive owned 2 v6 4spd cars and they are great for driving around town. They do make the engine seem pretty busy on the highway though. 80mph is about 3000 rpms vs the getrag being around 90 at 3000. But at that speed my 86 still gets between 25 and 28 mpg.

Depends on what kind of driving you intend to do. If you're going to be doing a lot of highway cruising, then you want the Isuzu. But if you're planning on driving the car hard then use the Muncie - as long as it's the Muncie that goes with the V6; the '84 Muncies are weaker and won't hold up.

If you put the Isuzu in and then do some drag racing you'll break it ...

I prefer the isuzu because I only paid $160 for it and at 70 in fifth my stock Formula 2.8 is turning around 2200 rpms. It replaced a getrag with a bad third gear synchro. The 3.65 Muncie in my '86 GT is doing around 2800 at 70 in fifth. My first Muncie also had a bad third gear synchro.

If Maryjane ever puts an Isuzu in his Fiero, he'll love it for road trips. I'm guessing he's doing about 3,000 rpms at 70 with his 4.1 Muncie. That Duke will be much happier at the lower rpms.

quote Originally posted by Rhino88gt: 80mph is about 3000 rpms vs the getrag being around 90 at 3000. But at that speed my 86 still gets between 25 and 28 mpg.

I have an auto with a V6 and I am wanting to change to a 4speed. Right now at 70 mph the engine is at 3000 rpm's. So does that mean that I may do better with the 4spd as far as mileage and performance?

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email: fierodustin@yahoo.com
PROJECT: 86 GT with a 3800SC Series I
My Home Page

quote Originally posted by fierodustin_86: I have an auto with a V6 and I am wanting to change to a 4speed. Right now at 70 mph the engine is at 3000 rpm's. So does that mean that I may do better with the 4spd as far as mileage and performance?

yes you will see an increase in both if you know how to drive a stick properly.

I'm not sure wich of these two I have, the 84 Fiero's econo 4spd or the Citation 4spd. Either way it seems I have the 3.32 axel ratio. So you're saying that it won't hold up to high power engines? This isn't good news for my planned swap! What can I do to keep the gearing but increase it's strength?

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1984 Fiero Sport Coupe
RPO list of this car

Pull a junker from a V6 in a 1985 (or most of 1986) and swap out the guts. You'll have a pretty badass transmission going. Though, many people have used the transmissions from the '84, but I never hear how the hold up.

I'm actually sort of shoked that most people would prefer the Isuzu over the 4 speed muncie. I mean, the shift from 1st to 2nd sucks (really). Not to mention, if you're in the city 4th gear in the isuzu is 1.04 as opposed to .81 iirc. 'course, when you get on the highway (or, if you're like me, and just forego the fourth gear altogeather)

quote Originally posted by binarycode: I'm not sure wich of these two I have, the 84 Fiero's econo 4spd or the Citation 4spd. Either way it seems I have the 3.32 axel ratio. So you're saying that it won't hold up to high power engines? This isn't good news for my planned swap! What can I do to keep the gearing but increase it's strength?

[This message has been edited by Jeremiah (edited 05-16-2005).]

Sorry to hijack but what company is the one that still produces the dog-box gears for the muncie. All I remember is that they wern't cheap but were pretty indestructable. Think they were used in the IMSA cars.

I had swapped a fiero isuzu and a cavalier isuzu into my 3.4 purshrod fiero and the 2nd gear shift was not a problem with the added torque it out accelerated my friends 3.4 getrag every time.. I also loved the buttery smooth shifts..

but I had no problem destroying the isuzu

I've never been able to break a 3.65 4speed.. I've had one wear out its synchros partially due to a failing clutch - but never broken one

and it was a bit better for performance.. won't get quite as good of milage but its a much more reliable tranny

as for the dogbox - here is what you need https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20050410-2-056633.html

[This message has been edited by Kohburn (edited 05-17-2005).]

What happens when you wear out your synchros?

quote Originally posted by Kohburn: I had swapped a fiero isuzu and a cavalier isuzu into my 3.4 purshrod fiero and the 2nd gear shift was not a problem with the added torque it out accelerated my friends 3.4 getrag every time.. I also loved the buttery smooth shifts.. but I had no problem destroying the isuzu I've never been able to break a 3.65 4speed.. I've had one wear out its synchros partially due to a failing clutch - but never broken one and it was a bit better for performance.. won't get quite as good of milage but its a much more reliable tranny as for the dogbox - here is what you need https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20050410-2-056633.html

quote Originally posted by Jeremiah: What happens when you wear out your synchros?

you split the case and replace em

or did you mean with a dogbox? dogbox = no syncros , can shift at any rpm, but need to revmatch/double clutch to drive smoothly around town

[This message has been edited by Kohburn (edited 05-17-2005).]