Torque converter question

Posted by: fenster

Torque converter question - 10/15/20 10:14 PM

This week I've been working on a transmission swap. My car is a 2005 Crown Vic, and the transmission was removed from a 2005 Grand Marquis. The tag on the original transmission indicates a 10/2004 production and the tag on the replacement transmission indicates 04/2004 production.

My dilemma - The replacement has a larger torque converter. Assuming that both converters are in good condition, is it important that I use the larger or smaller?
Posted by: TheShadow

Re: Torque converter question - 10/16/20 12:12 PM

Considering what you found fluid-wise in the original tranny, I would stick with the 'new' TC that came with the replacement. The difference between the two will probably never be felt, or needed, by 95% of the people who drive these cars.

You'll never get all of the debris out of the old TC, and that's likely what did damage to the internals of the old tranny's internals.
Posted by: BigMerc96

Re: Torque converter question - 10/16/20 01:15 PM

^^What he said. If it has a larger torque converter than what you had, then your car must be a P71. If that is the case, then you'll find the Grand Marquis transmission is actually shorter. You'll either need to use the steel GMQ driveshaft, or get a spacer for the pinion flange to use the aluminum driveshaft. You can use the aluminum driveshaft without a spacer but it doesn't leave very much spline contact at the transmission end so its not ideal. P71s and Town Cars (because they have a 3" longer wheelbase) use the longer output shaft so that they can use a shorter/lighter driveshaft while the rest used the shorter version. A lot of trucks also used both versions depending on wheelbase.
Posted by: fenster

Re: Torque converter question - 10/16/20 08:19 PM

Good info, thanks to both of you. My car is actually an LX and the donor car a Grand Marquis, so I'm not sure why mine would have the smaller converter. Regardless, the fluid in both transmissions is clean enough that I don't have a fear of using either converter. I'll take some measurements on everything tomorrow and see what I have.


Originally Posted By BigMerc96
^^What he said. If it has a larger torque converter than what you had, then your car must be a P71. If that is the case, then you'll find the Grand Marquis transmission is actually shorter. You'll either need to use the steel GMQ driveshaft, or get a spacer for the pinion flange to use the aluminum driveshaft. You can use the aluminum driveshaft without a spacer but it doesn't leave very much spline contact at the transmission end so its not ideal. P71s and Town Cars (because they have a 3" longer wheelbase) use the longer output shaft so that they can use a shorter/lighter driveshaft while the rest used the shorter version. A lot of trucks also used both versions depending on wheelbase.
Posted by: RF_Overlord

Re: Torque converter question - 10/16/20 08:28 PM

Originally Posted By fenster
My car is actually an LX so I'm not sure why mine would have the smaller converter.
Maybe your car is a police impersonator... biggrin
Posted by: fenster

Re: Torque converter question - 10/16/20 09:26 PM

Originally Posted By RF_Overlord
Originally Posted By fenster
My car is actually an LX so I'm not sure why mine would have the smaller converter.
Maybe your car is a police impersonator... biggrin


Just doing some reading, here's what I see:
- P74, so LX.
- Dual exhaust
- 3.27 axle code (Z5)
- Smaller (11.25" I guess) torque converter

This would seem to indicate the HPP model, though if I'm reading correctly HPP wasn't offered as a package in 2005, only as an LX Sport. This car doesn't have the rest of the LX Sport stuff like the floor shifter/console.

I'll upload some pics after I figure out how it works on this site.
Posted by: fenster

Re: Torque converter question - 10/17/20 01:18 PM

Both transmissions measured the same, so no issues so far. I just finished the dance of lining up the bellhousing and converter and got a few bolts in to lock everything in place. I'll get back at it after a lunch break.