I have a 700R4 which needs to be rebuilt. I have been told that the tv
cable on that particular transmission should probably be installed by a
pro. I have also been told that the cost of rebuilding the 700R4
(including paying someone to properly install the tv cable) and
purchasing a rebuilt TH400 (which I can install) is about the same.
If that's right, are there any advantages of one over the other? Which
would you guys prefer? Is the tv cable all that tricky?
I am not knocking a THM400 as it was a good tranny in its day but that
day is long gone. The THM 400 (also called a 3L80) itself was replaced
with a the 4L80 in 92 which is basically a THM 400 with a OD, a
locking converter and a electronically controlled valve body. The
700R4 is a good trany when brought up to current spec and with a lttle
work can easily handle a big block too.. Plus about a 700R4, on
locking converter in 3 and 4th, no need for a computer for it to work,
a wider gear ratio range from 3.06 first to .70 OD (a ratio spread of
4.37 to loweest to highest gear), and a deeper reverse too (2.29 vs
2.07). It is also a bit shorter than a THM400 too. Minuses of a THM
400, limited gear ratio rage of a 2.48 first to 1.0 drive (a ratio
spread of 2.48) and no locking converter. In a 4x4 you can have your
cake and eat it to with a 700R4 because you can run deep axle ratios
for seriuos power and still cruise nicely in OD. An extreme example of
this is that you can run 5.13's with a 700R4 and have a lower cruise
RPM than with a THM400 and 3.73's. This means the with 3.73 and a THM
400 you first gear start up is 3.73 x 2.48 which equals 9.25 to one.
Add a 2 to 1 converter stal that give you a maximum ratio factor of
about 18 to 1 (300ft lbs in to tranny about puts 5400 ft lbs on axle
shaft before drive train losses. With a 700R4 and 5.13's you have 5.13
x 3.06 equal 15.69. Add a 2 to 1 converter stall and you have about 31
to 1 startup ratio or 300 ft lbs in equals over 9000 ft lbs on axle
shafts. High possible axle torque and lower cruise RPM than a THM400,
this is why I say its day is passed.
TY SnoMan, How about the difficulty of the tv cable? I have found
several solutions online that promise easy install but the effort seems
to be in "dialing it in". I'm a little nervous because one thing I read
says the tv cable is vital for the survival of the 700R4.
The cable is not hard to adjust with a little trail and error and
common sense. GM has been using TV cable since 69 when THM350 came out
and it is not big deal to setup nor are you going to wreck your tranny
dialing it in.
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