Car is an '81 Cadillac deVille diesel. The transmission won't shift into
overdrive and the torque converter won't lock up. This started very
recently; before that it worked fine. Any ideas what exactly is causing
this, what it'll take to fix it, and how likely it is to leave one
stranded (local, mostly non-highway driving)?
Would a 700R4 be a drop-in replacement for the 200R4? Bell housing,
driveshaft, shift linkage, etc.? If I'm looking at major work on the
200R4, this would seem like a good option.
Thanks for any replies.
IIRC, the 200R4 has the BOP bolt pattern (Buick-Olds-Pontiac) whereas
the 700R4 has a Chevy bolt pattern.
I also seem to recall that the 200R4 is the stronger of the two in
factory form, although both can be custom built to handle any reasonable
amount of power you want to throw at them.
4th and lockup not working is a result of the 4th gear
clutch pack or band getting toasted because the lockup
wasn't working, in the first place ( to keep things cool) .
It's only controlled by a solenoid, which is fairly easy
to change, but probably wont make any difference now.
I've worked with cars that use both transmissons. They,
both, bolt right up to the same bell housing. Out of the
box, the 700 is the stronger. You can build both to handle
a lot of HP. The obvious differences are the 200 is
narrower in the pan area, so changing might induce problems
with the exhaust routing. The big difference is in the
gearing. If you had a 200 you wouldn't like a 700..
Anyone have any ideas on this? I'm trying to learn enough to decide
whether it makes more sense to fix the 200R4, or swap it for a 700R4.
On Sat, 8 Mar 2008, email@example.com wrote:
Besides mine and yours, I've seen 2 replies. Have there been others? I
was kind of hoping BobJ would expand on his answer a bit because it
sounded circular to me, but maybe I didn't understand him correctly.
In the meantime I've gotten hold of a factory manual for the car, and
according to the 200R4 diagnosis section, it doesn't look like there's a
single cause that'll take out both 4th and lockup, which was my initial
assumption. They both stopped working at the same time; if there was a
time when 4th worked and lockup didn't, it was very brief.
Well, I'm here... How could you tell your lockup wasn't
working beforehand. It's entirely independent from the 4th
gear circuit and generally, engagement is very subtle. The
lockup is there to prevent the TC from slipping and causing
excessive heat, especially when in 3rd and 4th. 4th is
worse because it is OD and the strains on the TC are
immense. The oil temp can climb over 260 degrees in a very
short time and cook your 4th gear clutches, which is
probably what happened.
In a car with an trans Control unit, there should have
been a code once the TC lockup solenoid malfunctioned. The
lockup can be applied in 3rd or 4th. Once the temp got into
the destruct range, the trans should have gone into 'Limp"
mode, with lights flashing, etc..
A lot of things could have caused the problem. When was the
last time the trans fluid was serviced...
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