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Replace 4 speed trans with 5 speed issuzu trans? by ltlfrari
Started on: 01-23-2019 10:11 AM
Replies: 15 (378 views)
Last post by: hnthomps on 01-30-2019 08:45 PM
ltlfrari
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Report this Post01-23-2019 10:11 AM Click Here to See the Profile for ltlfrariClick Here to visit ltlfrari's HomePageSend a Private Message to ltlfrariEdit/Delete MessageReply w/QuoteDirect Link to This Post
I always likes the gearing of the 5 speed issuzu trans on my old 4 cyl 85, especially on the freeway.
My current v6 85 has a 4 speed box in it and it's reving at 3000 on the freeway so it occurs to me that I could put a a 5 speed box in there and be much happier.
Wondering if anyone has done this and if so, what would I need to change.
I assume the trans mounts, the shifter and new shift cables but would I need a new clutch and how about axles, would they need to change?

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MulletproofMonk
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Report this Post01-23-2019 11:34 AM Click Here to See the Profile for MulletproofMonkClick Here to visit MulletproofMonk's HomePageSend a Private Message to MulletproofMonkEdit/Delete MessageReply w/QuoteDirect Link to This Post
I bought an 86 with the 2.8L and Isuzu. It was okay. It felt like the Isuzu didn't transfer the power from the V6, but I don't remember what first gear was like. My beef with the getrag is it feels like you are in and out of first gear quik. It almost feels like a granny gear on a truck. I always preferred the gears on the 4 speed, aside from not having a cruising gear as you said.

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Daryl M
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Report this Post01-23-2019 12:47 PM Click Here to See the Profile for Daryl MSend a Private Message to Daryl MEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just out of curiosity, hot tall are your rear tires?
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fierofool
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Report this Post01-23-2019 02:03 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I've had 2 85GT's that I put Isuzu transmissions into. First gear is a little short, but once you're into 3rd, you can just about run all day in it. It holds up well behind the 2.8, even with a moderate amount of abuse. I never dumped the clutch or tried to burn rubber in any gear. The first one got about 125000 miles on the Isuzu before I sold it.

The second one is with it's second owner, still on the road, but I've lost contact with him and have no idea how many miles it has.

To do the changeover, all you need is the shifter, cables, and throwout bearing and rewire your backup lights to operate from the transmission switch instead of from the shifter switch.
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fieroguru
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Report this Post01-23-2019 02:18 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
The first transmission swap I did was to put an isuzu in and 86 SE with 2.8.
I don't think I changed the shifter, just pulled the reverse lockout parts off it.
Swapped over the isuzu cables, transmission mounts, throwout bearing (I don't think I ever messed with fixing the reverse lights).

I was young, so lots of WOT upshifts and other antics... eventually pushed 5th gear out the end cap doing 135+ mph...

I did the same swap a couple more times as I preferred the ratios of the isuzu to the 4 speeds, even with the short 1st gear. Even ran the isuzu behind a 282 whp SBC until I upgrade to the getrag.
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olejoedad
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Report this Post01-23-2019 04:33 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
All Fiero manual transmissions use the same axles, side for side.
The clutches and throw out bearings are not all the same for all transmissions.
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fierofool
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Report this Post01-23-2019 04:59 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I've heard of people having clearance problems when installing an Isuzu into the Fiero, but I don't remember the specific year or what clutch kits they used. I do know that on both my 85's, I left the LUK clutch and pressure plates in them, without issue. LUK is the only clutch kit I've ever used in any of my cars.
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Raydar
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Report this Post01-23-2019 08:14 PM Click Here to See the Profile for RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
You might be able to get away with the same clutch and pressure plate, but you will need the Isuzu throwout bearing.

I had an Isuzu, bolted to a built 3.4, after I blew up my Getrag.
The same spec clutch worked fine for both, with the exception of the throwout bearing. (Not really helpful for a 4 speed, but FWIW...)

If you do this swap, just be careful not to shock-load the trans. No clutch drops, speed shifting, etc.
I know an old autocrosser who bolted an Isuzu to a 4.9. 2nd gear was the first to die. Several times.
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pmbrunelle
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Report this Post01-23-2019 08:53 PM Click Here to See the Profile for pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had an Isuzu for 8 years and about 50 k miles with a 2.8 without issue.
If I had to guess, I probably launched the car about 25 times a year from 5000 RPM.

I don't completely sidestep the clutch though; I do hold it at the friction point.

I still have those driveaxles for my new project (using a Muncie)... not sure if they'll snap due to a prior hard life.

[This message has been edited by pmbrunelle (edited 01-23-2019).]

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ltlfrari
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Report this Post01-24-2019 09:37 AM Click Here to See the Profile for ltlfrariClick Here to visit ltlfrari's HomePageSend a Private Message to ltlfrariEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well know the suzzy trans will stand the power, I had one behind my DOHC and it was fine although I never just dumped the clutch but it withstood plenty of 'spirited' starts!
As said, 1st gear is a bit short. OK, a lot short, with a BIG jump to second but you gotta love that low gearing in 5th on the freeway.
Wheels are stock 15 inch so no great big lump of sticky rubber to tie things up.

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Report this Post01-26-2019 11:44 AM Click Here to See the Profile for fierosoundClick Here to visit fierosound's HomePageSend a Private Message to fierosoundEdit/Delete MessageReply w/QuoteDirect Link to This Post
I still think the Getrag is a better match because 1st gear isn't so short.
You also have the FWD cars with Getrags as a source.
//www.fiero.nl/forum/Forum9/HTML/000038.html

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Report this Post01-26-2019 05:01 PM Click Here to See the Profile for pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierosound:
I still think the Getrag is a better match because 1st gear isn't so short.


Strange you say that, because the Getrag has an overall shorter 1st than the Isuzu.

Getrag:
3.61 final x 3.50 1st = 12.64 overall reduction

Isuzu:
3.35 final x 3.73 1st = 12.50 overall reduction

It's probably the jump to 2nd that has tricked you.

[This message has been edited by pmbrunelle (edited 01-26-2019).]

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fierosound
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Report this Post01-26-2019 06:21 PM Click Here to See the Profile for fierosoundClick Here to visit fierosound's HomePageSend a Private Message to fierosoundEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by pmbrunelle:

Strange you say that, because the Getrag has an overall shorter 1st than the Isuzu.


So then the people with Isuzu's have it wrong...
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Raydar
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Report this Post01-27-2019 07:22 PM Click Here to See the Profile for RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierosound:

So then the people with Isuzu's have it wrong...


It just appears that way. Although things are not always as they appear.

(I had an Isuzu in my 3.4 car, for a while - after I fragged a tired Getrag with it. First gear was okay, but I found the jump between 1st and 2nd to be... rather annoying? OTOH, third gear seemed to pull forever.)
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Report this Post01-30-2019 01:35 PM Click Here to See the Profile for ReallybigSend a Private Message to ReallybigEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am running an isuzu with a 4.9. Second trans, but it took 6 years to kill the first, which had 120k mikes on it. Yup, second gear stripped. Pulled her apart to have a look... those tiny gears are so cute! Never really dumped the clutch but would launch hard. So 6 years isn't too bad with 275 ft/lbs. First gear is s bit light but second is a stretch for using to get moving from a dead stop, but do-able. I live outta town with a drive into the city at 65mph. Makes the 5th gear worth while
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hnthomps
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Report this Post01-30-2019 08:45 PM Click Here to See the Profile for hnthompsSend a Private Message to hnthompsEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had an Isuzu with a 3800 SC engine in an 88 Fiero and drove it about 1000 miles before selling it to a friend. No problems at all with the combo but I deliberately drove it rather tamely and did not do high rpm clutch dumps.

Nelson
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