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Old 12-28-2004, 04:05 AM
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TH-350 to 2004r or 700r4

I have been doing searchs on the board here for a hour or two reading about the 700r4's and 2004r's.

i have a 1982 pontiac grand prix with a TH350, but once i change the rear gears out i will be in the 2800+ RPM depending on what gears i decide to go with so a O/D would be nice. i just bought a new crossmember and had to pay $250 by the time it got here so if i need to replace it i will forget about the swap and just pick out some differnt rear gears.

The trans will come from a junk yard car or the paper and would run as is. so aprox how much HP and torq can a stock 2004r and 700r4 handle?

what are the mods neeeded to swap?

2004r
-shifter
-shorten driveshaft (unless TH350 has the short tail shaft? but if its differnt i could probaly get the driveshaft off the car i get the trans from because they came in the same type of car i believe)

700r4
-shifter
-shorten driveshaft


Thank you for your time

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Old 12-28-2004, 05:03 AM
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The proper throttle cable and set up is a must. You will fry this transmission in no time at all without it.
2004R / TH350 short are a bolt in conversion.
If you go with a 700R4 the drive shaft will have to be shortened about 3".
Yokes are the same.
Cooler line connections are a bit different.
You will need the filler tube / stick for the new one.
The shift quadrant should be changed to accomodate the extra range.
The convertor cover will be needed too.


rossa ruck

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Old 12-28-2004, 07:30 AM
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The nice thing about the 200R4 is it is the same length as the manual trans and the TH350, plus they all share the same yoke.

I switched from a 200 to a 200R4 from a Monte Carlo SS. It came with a 3.73 speedometer gear. One thing you will find is that just about every speedo gear in used 200R4s seem to be frozen to the case. So if you have to change gears do it BEFORE you install it.

Mine is behind a warmed over 406 with a 3.42 rear gear. I get very good mileage and I can live with the speedometer being a little off.

I really agree with Stu's comment about the TV cable adjustment, but you'll have that with either the 200 or 700.
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Old 12-30-2004, 02:45 AM
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Thank you for the replys

so is there any crossmember modding or anything else to get ethier one of these trannys to fit in?

anything else i should know before i start hunting for a one of these transmissions?
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Old 12-30-2004, 05:42 AM
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The bolt hole where the trans mount goes through on the crossmember WILL be in the wrong place, you can simply measure the differences and cut the mount off from the crossmember and weld on a new piece with the hole in the correct place.

Measure twice, cut and weld once.
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Old 12-30-2004, 06:56 AM
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About ten years ago I swapped the trans and diff from a 87 Monte SS into a 80 Monte that had a turbocharged V6 and TH 350.
The swap is very straight forward, as others have said the driveshaft is reusable without modification, I had to fabricate a bracket for the TV cable to attach it to the throttle.
For the trans mount I used the original crossmember from the 87 Monte, the mount on the trans is further back than the 350 so the crossmember has to move back also, there were already holes in the drivers side of the frame that lined up correctly. On the passenger side the crossmember ends up in an open area of the frame. (your 82 should be the same) I had a friend with a Monte SS and I used it for measurements then fabbed a bracket for the crossmember to sit on and bolted it to the frame.
I used a lockup converter. (aftermarket) For its operation I found a company called Rossi Transmissions out of Calif. that sold a kit to make the lockup function work without an ECM.
I later swapped out the turbo 6 for a stout 355 smallblock and the trans was still going strong a couple of years later when I sold the car. I had the trans rebuilt and beefed up before its initial install.
Just recently I found a web site that gave the torque capacities of GMs transmissions. I thought I saved a link to it but at the moment I am not sure where it is. If I remember correctly it had stated that the THM 200R-4 was capable of 450 lb ft of torque with some modification.
I think that covers the swap, I loved the combination 3.73 gears for going and OD with lockup for cruising.
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Old 12-30-2004, 11:14 AM
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Quote:
Originally posted by 1ownerT
I used a lockup converter. [color=yellow]The 2004R and 700R4 BOTH only came from the factory with lockup converters[/color] For its operation I found a company called Rossi Transmissions out of Calif. that sold a kit to make the lockup function work without an ECM.
[color=yellow]The ECM is [/color][color=red]NOT[/color][color=yellow] necessary for functioning lockup for EITHER of these transmissions.
In fact the ECM's used in the infancy stages in the early '80's actually did very little until some sort of fuel injection was added to the equation.[/color]
I think that covers the swap, I loved the combination 3.73 gears for going and OD with lockup for cruising.
[color=yellow]I have the TH-700R4 and 3.73 gears for the exact same reason.[/color]

Last edited by M&M CUSTOM; 12-30-2004 at 11:18 AM.
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Old 12-30-2004, 11:19 PM
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M&M, Thanks for your edit, but I am well aware that these transmissions only came with lockup converters. There are options from converter manufactures to use NON-lockup converts, that is why I mentioned I used a lockup.
The lockup converter needs an electrical current to engage the lockup, via the TCC solenoid and the ECM. The 87 Monte that my trans came from had several sensors that were monitored, as was the carburetor, granted it was very primitive by todays standards.
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Old 12-31-2004, 12:37 AM
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All the trans experts I asked at a trade show recently told me if your going to use an od trans hard, use the 200r4. one of them told me the 200r4 had a better over drive.
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Old 12-31-2004, 01:05 AM
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attached is a picture of my new crossmember i just got. would it be ok to just get a steel plate put a hole in it, bolt it to the stock tranny mount on the crossmember then drill another hole in the bracket where the tranny can bolt up to it? or does the mount need to be in the other direction?

just spent $250 on the crossmember by the time it got here and to cut it and weld a new bracket on wich i also dont know how to weld worth **** yet plus the fact if the tranny doesnt work and needs to be swaped back to the TH350.

thanks for everyone that replyed, good info!
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