J-Body Automobiles Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
270 Posts
Discussion Starter · #1 ·
Just wondering from any of you that actually have swapped in a 5 speed in a J with a 3.1 did it affect mpg at all?
My 89 Z has a 93 3.1 in it, and auto 3 speed, and i can get a 5 speed for a decent price, i am not into racing, just a occasional blow by of idoits on the highway LOL.. So i am not figuring in anything performance wise.
But normally i drive casual, and near speed limits. And wondering if the swap woud be worth it in as far as only talking mpg.
I posted elsewhere that it was getting around 28 mpg, but wife did calcs. wrong, its more like 22-25. Would a 5 spd get any better or worse?
I always see a stick is supposed to get better, but real world means more than what you see on paper.
And i didnt ask about different cars, one with auto, one with 5 spd. because 2 different cars can/do get different mpg anyway, more interested in a swap in the same car where everything else stays the same.
 

·
Registered
Joined
·
4,233 Posts
5 speed will be better for highway of course, but you need more than just the transmission to do the swap. Check out the How-to section as there are 2 5 speed swap write ups on there.
 

·
Registered
Joined
·
1,557 Posts
There is a improvement, rpm's are down on the highway which makes you burn less fuel :wink: Depending on how you shift it ill be better in the city also :p

My opinion 5spd gets more miles to the gallon :wink:
 

·
Registered
Joined
·
270 Posts
Discussion Starter · #5 ·
yes i know i need more than transmission, i would have whole car to get all the parts from, though i would use a new clutch, plate, and bearing.And turn flywheel.

If the rpm's are down on the highway, do you know by how many? going my my speedo/tach, my car says 2500 rpm @ 55

And did i read right my stock ECM will work? tho i can get the one from the stick car, it isnt running so no way to know if its good or not.
 

·
Registered
Joined
·
1,642 Posts
your car will run with the auto ecm, need the 5 speed chip tho... or else your tach wont work. figured that out the hard way. only other thing i know to tell you is that in 5th for me. at 65 im around 3100 or so.. ruffly, i aint drove it in a wile. but ill check next time we go out.
 

·
Registered
Joined
·
3,794 Posts
Yes, you will get quite a bit more mpg on the highway. Plus, the th125 is junk in stock form. They drain gas and power. You'll get a good bit of power back with the manual.

My 3speed 2.8L Turbo Fiero got extremely shitty mpg on the highway. I'm talking about ~4000 rpm & full boost on the highway @ 80 mph. :lol: You don't get good gas milage when in boost. :wink:
 

·
Registered
Joined
·
270 Posts
Discussion Starter · #10 ·
thanks for the replies guys, seems the best thing to do is put the 5 speed in.

I know there is probably a how to on this question, but putting it in my 89. Are there 'better/best" parts to use from different years even if i have a whole car to strip?
Because if another year car has a better part, i would rather get that part even if i have to buy new,and make it as good as i can all in one shot.
 

·
Registered
Joined
·
4,233 Posts
1fastcavi said:
your car will run with the auto ecm, need the 5 speed chip tho... or else your tach wont work. figured that out the hard way. only other thing i know to tell you is that in 5th for me. at 65 im around 3100 or so.. ruffly, i aint drove it in a wile. but ill check next time we go out.
That is incorrect. Tach goes off the white wire on the coils :p
 

·
Registered
Joined
·
1,642 Posts
got the stock chip out and put in bens chip, and at 65 mph in 5th i was at something around 2500 idk wtf was wrong with the stock chip O_O
 

·
Registered
Joined
·
4,233 Posts
1fastcavi said:
got the stock chip out and put in bens chip, and at 65 mph in 5th i was at something around 2500 idk wtf was wrong with the stock chip O_O
That sounds almost right...I think 65-70 is around 2700 RPM

I used an 89 Memcal in my 92's ECM and my RPMs were just fine. I just didn't have a speedo!
 

·
Registered
Joined
·
270 Posts
Discussion Starter · #14 ·
Ok, a few questions about my auto tranny, now i didnt write it down this morning, so trying to remember exactly, here how it works as best as i can explain,
First off, accelerating normal away from a stop, it shifts out of first within 1 car length, and out of second in about 2 more car lengths, to me, this doesnt seem right, my lumina with a 3 spd. auto didnt do this. Nor did my daughters Corsica LTZ with a 3.1 3 spd.
And no amout of cable adjusting helps. Strangest part is if i try to go by the book and adjust kickdown cable, the car wont up shift till rpm's are WAY to high, just seems like it has 2 positions, like it is, or totally wrong.

Also like when letting it in low gear, engine holding it back, closed throttle going down a fairly steep country road, my Z hold back at about 15-18 mph, and tach is up around 2k. I drove daughters LTZ over this road the same way and it didnt hold back nothing like my Z does.
Now... when accelerating from stop pretty fast, and manual shifting it, it sounds like its screaming in low gear at 25 mph, tho tach is at about 2300, that doesnt make sense to me, but anyway, under medium fast accel, it still wants to change out of low to second within 20 feet, and then 3rd about the same distance, it will be in 3rd gear, and converter trys to lock at approx. 30-32 mph.
And at 45 mph, tach reads 2000ish
at 50 mph, tach reads 2500ish
60 mph approx 3400ish
Does all this sound normal? sure doesnt seem like it is to me comparing it to the LTZ. I drove that LTZ with unhooked TCC for awile, and it still, from memory, didnt run rpm's like my Z does
but maybe its cause i am new to Z's? or........ would it act this way if someone had put a 4 cyl. automatic in it? i dont know the cars history. And assuming from what i read, a 4 cyl auto will fit right?

Anyway to tell the difference between a 4 cyl. auto and a V6 auto? (again, assuming one could be in it)

I cant get the 5 spd i was going to get because after further investigation, i now am told the 5 spd had major problems inside.
So as of now, just trying to understand and find out if mine is right in as far as proper tranny in it, and all the above crap.
thanks for anyones indulgence in helping
 
1 - 14 of 14 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top