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Thread: 4 Speed to 5 Speed Swap. Who's done it.

  1. #1

    4 Speed to 5 Speed Swap. Who's done it.


    Now that I've gotten "input" on Auto to Manual Swap, Has anyone done a 4-speed Manual to 5 Speed Getrag Swap.

    I've found a local 4 speed car complete with motor blowing smoke and another guy who gave up the idea of his Auto to 5-speed swap. (Rebuilt Getrag ready to go From Grand Prix).

    I've searched the archives here and on some other forums. As not to confuse anyone, give me your Input. the scenario now will be:

    Car will be weekend (mabye not even that) Driver

    The V8 Dyno'd @ 323.11 HP at Rear Wheels. (86 Z-28). I'm estimating 330-340HP at the flywheel give or take. (for "Fiero purposes")

    1. Of course the 5-speed is the "prefered trans" but give me you opinions on keeping the 4-speed and doing a complete swap from the other GT.

    I'll be doing:

    - Removal of the Th-125C from the 1985
    - V8 Conversion for the 1985
    - 86 complete 4-speed (v6 car) for the Manual Donor which is complete.

    On one hand, The complete car will make for an easier Manual swap (But them I'm using the 4-speed). On the other, The 5-speed (I'm guessing) will require a bit more "Part Finding" etc. I'm guessing that linkage, etc will need to be reworked, shifter etc. Give me your thoughts:

    V8 4-speed swap (and of course I'll beef up the 4-speed) or V8 Getrag swap. I'm not "too concerned" with the extra gear of the Getrag or "highway" cruising. But I also don't want to be destroying the 4-speed. From what I've read, the 4-speed seems to be hanging in there with the V8 Archie Swap and some of these hopped up 3800SC's.

    Fire away


    Previous Builds: AF - 308 Replica w/ V8 & GM F-body Testarossa Replica
    Current Toys: 308 V8 Project #2, 91 V-12 Jaguar XJ-S Coupe. 1983 Hurst\Olds, 1979 Trans/AM - 468CID Bracket Car.

  2. #2

    Re: 4 Speed to 5 Speed Swap. Who's done it.

    I Just noticed Rodney Dickmans site. With the swap info, Good info. Lots of questions answered. Anyones personal opinions would still be helpful.

    Previous Builds: AF - 308 Replica w/ V8 & GM F-body Testarossa Replica
    Current Toys: 308 V8 Project #2, 91 V-12 Jaguar XJ-S Coupe. 1983 Hurst\Olds, 1979 Trans/AM - 468CID Bracket Car.

  3. #3
    Senior Member cowans's Avatar
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    Re: 4 Speed to 5 Speed Swap. Who's done it.

    Here's my .02! I started with a 85GT 4spd mated to my SBC. Always looking for 5th! I have a heavy foot and highways are always 70-80mph (125km). I couldn't stand it any longer, so I dropped in a 5spd Isuzu. I'm now on my 2nd Isuzu (2nd gear launches don't last). 1st gear in all Fieros trannys are a waste for a V8! All that to say is the Isuzu, when treated nicely, shifts smoothly and 5th gear won't make you stop for gas every 1/2 hour. Be prepared, gas stations are your best friend with a V8, you will visit them often enough! My 1st preference would be a Getrag, but they're 'gold' up here. I could trash 5 Isuzus before paying for a Getrag! The only negative I hera about a Getrag is 1st gear is pretty short. There seems to be some new instances of Getrag failures recently on Pennocks. You say your working with 325+ hp, put the Getrag in with some 'new' cables, GM Syncromesh oil, and do some research on the 'SPEC' stage 2 or 3 clutch, you'll be happy you did.
    Sandy

  4. #4

    Re: 4 Speed to 5 Speed Swap. Who's done it.


    Thanks,

    It's a shame, I considered leaving the auto (so the wife could drive) but I can't seem to find any info (or they just do'nt make any) - on shift kits / upgrades parts for the Th125C. I've got quite a few toys and I'm looking at a Viper Now so I'm not "dead set" on stick.

    Have you heard of any AUto performace items? I should post that in seperate topic.

    Previous Builds: AF - 308 Replica w/ V8 & GM F-body Testarossa Replica
    Current Toys: 308 V8 Project #2, 91 V-12 Jaguar XJ-S Coupe. 1983 Hurst\Olds, 1979 Trans/AM - 468CID Bracket Car.

  5. #5
    Senior Member cowans's Avatar
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    Re: 4 Speed to 5 Speed Swap. Who's done it.

    Don't waste your time with a TH125, it won't stand up to a V8! I'm not an auto person but I believe the 460TE or 480TE trannys are pretty good.(not sure if my number/letters are correct). Check Pennocks for auto trannies, Im sure there are 20 pages on it. Heh, there are some that are setup to shift through 'paddles' with the newer trannies!
    Sandy

  6. #6
    Moderator FunnyWheels's Avatar
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    Re: 4 Speed to 5 Speed Swap. Who's done it.

    I did the TH125 Automatic to Getrag 5 Speed in my car.* It was pretty involved.* I had to locate the following:

    Clutch pedal assembly

    new master cylinder

    new clutch lines

    new vibration proof flex lines on each end of the steel lines

    new short slave cylinder for a Getrag
    (some people will tell you to use the long one from an Isuzu but I figured GM didn't so why row the boat up stream)

    new release bearing

    new clutch

    new pressure plate

    new shift cables

    used 5 speed shifter assembly

    the Getrag shifter brackets from Rodney Dickman short shift kit

    new clutch pin rebuilding kit from Rodney Dickman

    short shifter shaft from Rodney Dickman

    and a used 5-speed Getrag

    I rebuilt the transmission with new axle bearings and seals.*

    But mine is only attached to a 3800.* It has been strong enough for other V8 users so I went with it.

    Give it a try.

    Dave


    Note short Slave.
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