[Amc-list] Re; 998 Lock up Torque Converter etc.

["John Elle" <johnelle@xxxxxxxxx>]

Keleigh
Snip
I finally got a trans for my Eagle. It's another Eagle 998, but
" unlike my current trans, it has a lockup converter. I'll probably like
" this, if it helps the mileage and noise on trips, but it means my
" current converter won't fit, and it didn't come with one. Should I
just
" get a rebuilt stock one, or since I may have to pay a core charge
should
" I step up and get an aftermarket one? I figured since it locks up, a
" higher stall one with more torque for towing and stuff would be nice.
" Does anyone make an RV type converter w lockup for the AMC 998? BTW,
" it's got an injected 4.0 in it, FWIW.
Snip
I put my 904 lock up transmission together in 1999. I had it rebuilt by
a qualified re-builder as I do not fell that I am one of those. It is a
1980 Lock up torque converter 904. 
Whether you run a lock up or not is up to you. I personally think that
it is a good idea for me and for what I have read for your Eagle
applications I think it is a good idea for you too! 
There were two lock up torque converters stock available in 1999. An OEM
equivalent low and high stall torque converter. I do not know the
recommended applications as to why there were two converters available
but I chose the low RPM lock up unit. The reason was that I was building
a street car and I wanted as little slip as possible for the purpose of
fuel economy. It locks up just off of idle. I really don?t like it. More
later. 
I also have a completely stock 1980 AMX with the higher stall torque
converter in it. I like the standing start performance better with it
than I do the one that  I chose for my Spirit. 
In addition I have the lock up speed changed in my Spirit by putting a
spring in the valve the controls the lock up that is weaker than stock.
The lock up occurs at 55 mph rather than the 37 or so miles per hour my
AMX does. This gives me an equivalent of a poor mans 4 speed automatic
as the rpms come down at high way speeds by (or should anyway) about 500
rpm. The AMX does about a 500 rpm shift when the transmission lock up
takes place and you can see it on the tachometer. 
My Spirit on the other hand with the ?tight? torque converter is pretty
much as tight as it is going to get by 30 mph and when the lock up takes
place at 55 you can barely see any rpm change what so ever. 
Which brings up the reason I do not like the low rpm or tight torque
converter I chose. When I switched from a carburetor to fuel injection I
lost measurable power between idle and 2000 rpm. With the torque
converter as tight as it is, (a low stall oem equivalent) I can not get
the engine up to the point where it develops power from a dead stop. It
there for is a decided slug until it gets up to 2000 rpm. As the lock up
function by the transmission only takes place in 3rd gear and is
dependant on accelerator pressure as determined by the kick down rod or
cable as the case may be the lack of grunt due to the tight converter is
felt in the lower gears. 
A drag strip comparison between my 1980 AMX and my 1980 fuel injected
Spirit makes my Spirit a half a second slower than the AMX, and a full
second slower than it was with a carburetor. 
However with the fuel injection if we were running ½ mile drags I could
pass a 16 second car with my Spirit some where beyond the ¼ mile point.
Where the AMX is a bit poopy and getting poopier at 80 the Spirit is
just catching it?s breath and beginning to run well. 
Both cars have the 2.56:1 rear axle. 
Thus I am in the market for a 2000 rpm stall torque converter which was
available after market for the AMC 904. I have not checked recently. 
As your Eagle is some what of a working car I would recommend the high
stall OEM equivalent torque converter and putting a weaker spring in
valve the controls the lock up function. 
If you have an old timy transmission guy to talk to he would remember
the kits that were available in the 70?s and 80?s to change the lock up
point of the torque converter to a higher road speed to avoid the
irritating hunting tendency transmissions of those years had. That would
be your best bet at the present time. 
If you want to eliminate the lock up, put a BB in the valve under the
spring to shut of fluid through it. But that is not what I would do. 
I have not read through the rest of the AMX files postings so maybe you
already have your answer, but this is my 2 cents for what it is worth. 
John. 
 
 
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