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Registered
1996 Sedan Deville 123.5K, 1997 Deville 91.5K
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35 Posts
Discussion Starter #1
Hello, gang! I bought a 1996 Sedan Deville about 3 1/2 weeks ago with 115K miles on the clock and I have been ecstatic about it! 52 years old and this is the first vehicle I ever bought in my life solely for the 'cool factor'. I'm looking forward to learning about my new rig on this forum.

I'm hoping I dodged a bullet on the dreaded HG failure I've become enlightened about. The first Cadillac I looked at and test drove was a 1999 Deville, the owners told me they had experienced an HG failure at approximately 106K miles. The significance of that statement didn't dawn on me until I started reading multiple posts on this forum.

Fortunately, it looks like my 96 model is statistically much less likely to have that problem, although a precise explanation seems elusive.....all I can do is make sure the coolant doesn't go bad and otherwise properly service my vehicle.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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70,751 Posts
Welcome to the Funny Farm !!!

Depending on time of day, pour a coffee, CocaCola or scotch and water and read all you can in here, Seville/Deville, Engines; Northstar, Tech Tips and any other forum of interest. Always look through the stickies in any forum of interest - timeless info. Study this - written by a GM Northstar Powertrain engineer - it applies mainly to the pre-1998 Northstar. https://www.cadillacforums.com/cadillac-tech.html.

You will see many differing opinions and advice in any worldwide forum. Shop carefully.

Don't sweat the head gasket (cylinder block head bolt hole thread failure) - drive it like you stole it and keep it clean. 1997-1998-1999 were the worst years, maybe due to block casting metallurgy changes. Look at the failure rate poll in Engines; Northstar.
 

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Super Moderator
2003 Deville Base
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5,340 Posts
:welcome: Welcome to the forums. You are sure to get lots of opinions and help here. As posted, read the stickies, and read your owner's manual at least twice. Be prepared with a thick skin--when you ask questions you'll get plenty of blunt, factual answers.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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20,124 Posts
:welcome: Welcome to the forums. You are sure to get lots of opinions and help here. As posted, read the stickies, and read your owner's manual at least twice. Be prepared with a thick skin--when you ask questions you'll get plenty of blunt, factual answers.
==============================================
read your owner's manual at least twice.
-------------------------:yeah: -----
and if you don't have the OM - go here for a free download -
https://justgivemethedamnmanual.com/cadillac/1996-cadillac-deville-owners-manual/
 

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Registered
Go ahead, blame me. Everybody does 🙄
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9,920 Posts
Congrats on the Caddy purchase, Ameierot :)
 

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Registered
1996 Sedan Deville 123.5K, 1997 Deville 91.5K
Joined
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35 Posts
Discussion Starter #7
Thanks for the warm welcome, guys! I'm looking forward pulling fault codes which I strongly suspect are related to the torque converter clutch and taking a look at why my electric antenna does not work. I'm sure there is plenty of advice available herein on both topics.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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70,751 Posts
If you don't quickly stumble across a solution in one of the forums related to the car/model and Northstar engine, Google something like "cadillac forums 1996 deville radio antenna" and/or "cadillac forums 1996 deville torque converter clutch".

For TCC, P 1860 means the actuator solenoid has failed - A $45 part buried $2500 deep in the transmission. P 0741 is failing shaft seals in the torque converter or transmission input shafts - those seals insure clutch activation oil pressure to the TC. To repair that requires total converter and transmission removal/parts/converter replacement. $4600.

You can drive the car forever with either code UNLESS it's subject to emissions testing.
 

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Registered
1996 Sedan Deville 123.5K, 1997 Deville 91.5K
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35 Posts
Discussion Starter #9
Thanks for the advice, Submariner! It is indeed the P(C)0741 code but it was listed as 'History' and hasn't reappeared since I cleared it. I presume it happens intermittently and will appear more frequently as the internal leak paths in the transmission get worse. No emissions testing in Iowa so I'm not inclined to worry about it until I kick back and retire in a couple years :). I need to be careful because I'm afraid I might be turning into a born again car-nut/gearhead like my three brothers!
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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70,751 Posts
The P 0741 code is funny (like: weird, not ha-ha) in the way it sometimes sets infrequently. IF it is due to the failing seals then, yes - it will appear more frequently as time goes by. No transmission or vehicle damage, though.

4th gear is the OD in these cars - 0.68:1. TCC removes the last 300 or so rpm of converter slip at steady road load speeds over ~41 mph. Here's your speed/rpm table with TCC engaged.

Your base Deville is a VIN Y car - 3.11:1 final drive. Speed limited to 112 mph, so the table stops there. (Y is the 8th character of the VIN)
 

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Registered
1996 Sedan Deville 123.5K, 1997 Deville 91.5K
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35 Posts
Discussion Starter #11
Very interesting, the eighth digit is indeed 'Y'. I have a three hour round trip tonight. Great opportunity to find a nice flat stretch of interstate on the riverbottom and see if my t/c clutch is engaged.
 

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Registered
1996 Sedan Deville 123.5K, 1997 Deville 91.5K
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35 Posts
Discussion Starter #12
I took the old girl out yesterday afternoon on a flat stretch smooth highway with about a 6 mph tailwind (according to my mobile phone). Set the cruise at 55 mph and when everything settled out the tachometer was reading 1550 rpm. Looks like the engine rpm is slightly greater than it should be if the t/c were locked up. Do those t/c lockup clutches employ friction elements that might be allowing for 1-2% slippage even though the clutch is engaged?
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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70,751 Posts
It's a viscous clutch, never TOTAL lockup. 1550 is close enough.

That speed/rpm table was done by mhamilton some years ago with input from over a dozen CF members with similar cars and the 4T80E transmission.

Here's the companion graph, so you can see that 1513/1550 is in the ballpark.
 

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Registered
1996 Sedan Deville 123.5K, 1997 Deville 91.5K
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35 Posts
Discussion Starter #14
I got my power antenna fixed! Thanks to you guys on the forum! Also identified the leaking area on my engine but that’s less exciting...
 
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