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7/23/16 9:53am - Original Message: 'Swapping a TH350 with a 700R4 - issues?'
bepah1
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Brentwood, CA - USA

Vette(s):
1979 Corvette project car

Joined: 4/15/2016
Posts: 21
I have pretty much decided to replace my 1979 engine with a crate LS3. Leaving the stock transmission in place seems wasteful with all of the power I'll have. What are the major issues with this replacements, other than getting a good torque converter?
 
Many thanks,
 
JC
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8/5/16 9:26am - Reply: 'Re: Swapping a TH350 with a 700R4 - issues?'
nosal1 Gold Member
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 238

Good Morning,You might consider going with a 200 R 4 trans instead of a 700 R 4 as you will have to do a bunch of work getting the 700 to bolt in place of where the Turbo 350 sits. The 200 R 4 is the same length as the 350 trans and will not require and cutting of drive shaft as you would have to do with the 700 R 4.I have researched this for my '80 Vette and have concluded that the 200 R 4 is the way to go and has a high gear ratio for 4th (.67-1) lower RPM at higher speeds.

Good luck in either way you go and have a Great Day today and everyday..       Sal C                                nosal1


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8/13/16 6:21am - Reply: 'Re: Swapping a TH350 with a 700R4 - issues?'
nosal1 Gold Member
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 238
Trans 1st Gear 2nd Gear 3rd Gear 4th Gear Reverse
Powerglide 1.76/1.82 1.00 --- --- 1.76/1.82
TH350 2.52 1.52 1.00 --- 1.94
TH400 2.48 1.48 1.00 --- 2.07
TH200-4R 2.74 1.57 1.00 0.67 2.06
TH700-R4 3.06 1.62 1.00 0.70 2.29
4L80E 2.43 1.49 1.00 0.75 2.07
 
 

THM200-4R[edit]

For the 1981 model year, the 200-4R (sometimes called 200R4) was introduced. The components which were prone to failure in the THM200 were improved, and this transmission was used with high-power applications primarily the Buick Grand National. The 200-4R was configured with several different torque converters and gear ratios depending on the vehicle application.

Unlike the 700R4, most 200-4Rs have a multicase bellhousing for use with Chevrolet, Buick/Olds/Pontiac (BOP), and Cadillac engines. However, 200-4Rs share mounting locations with the TH-400. Since the external dimensions are similar to the TH-350 (overall length, drive shaft yoke spline count/diameter and general size), 200-4Rs are often swapped in place of TH-350s in older vehicles to provide an overdrive gear.

Early models had PRND321 on the cluster, while later models had PRN(D)D21, with the left D identified as the overdrive gear by a square or oval ring.

The THM200-4R can be found in the following vehicles:

The THM200-4R was phased out after 1990; its final usage was in the GM B-body vehicles.



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