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3-spd tranny queston


mako's Avatar
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01-27-03, 05:59 AM   #1  
3-spd tranny queston

1986 Cutlass Supreme, TH200 tranny on a 307Y, car has 110K miles but this isn't the original engine (rebuilt for sure) or tranny (not sure of rebuild status).

The VIN on this car shows a 4sp tranny but it only has a 3 spd (judging by the number of shifts up to 65 mph and by the 11-bolt tranny sump pan/ square with shaved corner shape). So it's not the original. I have no clue how long it's been in there (bought car about a year ago).

Anyhow, I HATE the way this thing shifts. It works flawlessly, for a 3 spd. It shifts way before the engine gets wound up enough to develop what little horsepower it will muster, unless I'm gunning it.


For example, when I make a turn from my driveway, it's in second gear often before I even get the car straightened out on the highway. It shifts very smoothly and the tranny fluid is plenty full and bright red and clean.

Is there any "shift kit" that can be installed (by a novice or pro mechanic) that will get this vehicle to wind up higher on the RPM's during normal acceleration? Will I need to install a cheap TACH to monitor RPM's to make sure I don't redline it during more heavy acceleration (like interstate merging?)

Any help will be appreciated!


Mako

 
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01-27-03, 07:19 AM   #2  
Joe_F
First things first.

The Vin # will not tell you the tranny equipment. Only the RPO code sticker in the trunk (the one that says "DO NOT REMOVE...SERVICE PARTS IDENTIFICATION LABEL").

Tell me if you have MV9 or MW9 on that sticker.

MV9 is a three speed THM200
MW9 is is a 4 speed automatic, overdrive THM2004R.

You can look at your shift quandrant on the dash. Does it say PRND321 or PRND(with circle)D(without circle)21 or PRND21?

Let us know. Leave it stock. It is a gazorch to put in a 4 speed overdrive (it can be done though).

 
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01-27-03, 09:44 AM   #3  
The shifter column reads PRND21 .

I can't get to the car right now to read the sticker in the trunk- will post later.


The only reason I thought the VIN gave the tranny info is b/c I thought that's what CARFAX told me I had when I put the VIN into the system.

Agreed, I'm not interested in swapping the tranny to another type (even though I hate a 3 spd with a passion). I was just wondering if there were any reasonable modifications that can be made to adjust the RPM shift point to let the engine rev a little higher- I remember my brother putting a "shift-kit" in his old Fairlane and it pretty dramatically changed the way his acted, and he really liked it. (I know that a '66 C-4 tranny is a different animal by far than a GM THM tranny).

 
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01-27-03, 10:49 AM   #4  
Joe_F
You have a three speed THM200 based on your shift quadrant markings.

No, putting a shift kit in this will do little to it. It is a very weak and lackluster transmission. Most 307's of this vintage had the THM2004R instead. Suprising to see that in a 1986 model like that.

(It WAS an option to get a 4 speed ).

 
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01-27-03, 10:55 AM   #5  
I'm more and more seriously considering an engine/tranny swap. This engine runs smooth but the carb is just in bad shape (when the engine was replaced they obviously didn't replace the carb). I've had it checked out- the choke is fine but the rest of the carb is in bad shape, needs rebuild (I can't remember the actual problem but they know their carbs).

The car's build is in good shape, just some mechanical problems. I'm looking around for a good price on a 350/350 or 350/400 combination (on a rebuild or low-mileage engine/tranny).

I wish I was still in the upstate of SC- I knew a guy that had a 60-something 327 mated to a THM400 that was the bomb! He took it out of an old Camaro, rebuilt it and slightly modded it, added the tranny and meant to put it back into the Camaro but never did. He offered to sell it to my brother for $1000 (incl tranny). Sure wish I could find a deal like that......

 
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01-27-03, 12:36 PM   #6  
Joe_F
You're going to run into problems bypassing such things .

Get a pre 1981 one without a computer and this swap is 10 times easier and will look and run better. Stick with the stock motor in a 307.

You would fare better finding someone that can rebuild the carburetor and go through it soup to nuts. I challenge that my 307 runs better than any Chevy V8 out there. The 307 runs so smooth and is a great little engine. Just short in the power department.


 
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01-27-03, 04:52 PM   #7  
Joe,
Doesn't the '86 TH200 have a vacuum shift modulator? If so, that could very well be causing his problem. Could be either wiped, bad vacuum hose or some idiot tried to adjust it. Easy and cheap repair.

 
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01-27-03, 04:58 PM   #8  
Joe_F
Dan, to my recollection, it is cable operated, no modulator.

This is a very poorly screwed together tranny and VERY undersized for just about any V8 engine it's paired with. They puke out frequently. The 1979 and 1980 Pontiac dealer factory bulletin sets I have mention a lot of problems with the early ones.

 
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