Moparts Tech Archive

Automatic Trans.

Lock-up or non-lock up Trannies

Okay I know someone has asked this before but how do you identify a 727 trans (or 904)as to whether its a lock up on non lock up converter?
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John Russo
Moparts Member
Posts: 1837
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 04-09-2002 08:58 PM

With the trans out, and converter off the input shaft, a lock-up will have a smooth area on the end of the input shaft (no splines) for about 3/4", then the splines begin. Also, there will be a thru hole in the end of the input shaft lengthwise. The non-lock-up will have splines to the end of the input shaft and no thru hole. If the trans is in the car, pull the pan, and the valvebody. If it has a "S" shaped hollow tube on the top of the valvebody, it is a lock-up. John
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MPerry
Moparts Member
Posts: 2757
From: Leominster,MA. USA
Registered: May 2000
posted 04-09-2002 09:00 PM

The input shaft will not have splines at the very end of a lock up type transmission. ~Mike~
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Wheeler
Moparts Member
Posts: 511
From: Alberta, Canada
Registered: Oct 2001
posted 04-09-2002 10:10 PM

John and Mike are right on the money! In addition to what John & Mike said -
727 and 904 lock up trannys were introduced in the late 1970s - I think 1978 was the year.

Most Chrysler RWD passenger cars from 1978-1989 had lock up trannys. 1978-1983(approx) police cars were the exceptions, and there are also others I may not be aware of.

The lock up 727 tranny was available in passenger cars from 1978 to about 1982/83. After 1982/83, the 904/999 was the only available automatic in the RWD cars.

You could also get the lock up trannys in 1978-1987 Dodge Trucks, usually in the slant six and light duty 318 powered trucks. Trucks with heavier GVW's usually didn't get lock up trannys.
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5thAve
Moparts Member
Posts: 2807
From:
Registered: Jun 2000
posted 04-09-2002 10:56 PM

Here's an extra kick on this too... fleet package Diplomat/GranFury/Caravelles could be had with a 727 upto 89. I don't know what pacge you had to get for them to come with that option, but the driveshaft I'm running now, and my 727 linkages came out of an 88 Diplomat taxi. The kicker is that it was a 2bbl 318, not even a 4bbl!?!?!?!? I've heard of a few others running them, the one I raided looked all stock. Assuming these were lock up units, but don't know for sure.
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Wheeler
Moparts Member
Posts: 511
From: Alberta, Canada
Registered: Oct 2001
posted 04-10-2002 12:19 PM

69DartGT - I'm thinking the cop cars, higher GVW trucks/vans and fleet specials didn't get lock up trannys due to strength/reliability considerations. Lock up trannys are typically not as strong or durable as non lock up trannys. Cop cars, fleet specials and higher GVW trucks get driven hard, so Chrysler put the stronger non-lockup trannys in them.
My 1985 D150 is a heavy duty 1/2 ton, and it doesn't have the lock up tranny - I'm thinking ultra light duty 1/2 tons (Miser packages, etc) with the slant 6 and 318 have it?

5th Ave - what the???? I always thought the 727 wasn't available in M-bodies after 82/83. I remember reading something about it in the 1979-93 Chrysler cop car book. I gotta read my books again...
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curious
Moparts Member
Posts: 666
From: bronson (south west) michigan
Registered: Jul 2001

ok first thing is IMO it had some thing to do with reliability. not in the tranny but in the clutches in the torque converter it self. they prolly did not have the load capacity to pull heavy loads or high hp w/o slipping. there are "high performance" lock up converters out there. some handling nearly 1000hp+. those are gonna run around $750-$1000 for a 5 disc clutch pack high performance torque converter. long ago grand national guys found big time increases by controlling the lock up in the torque converter. this is usually accomplished by a electric switch, full throttle switch, rpm module, ect ect. but then they also soon found out that the stock lock up clutches couldnt handle full-throttle abuse. then perfromance converters came onto the market. i belive precision converters claims upto 7/10ths and 50hp @ the rear wheels due to the less slippage usually associated with a high stall converter.
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5thAve
Moparts Member
Posts: 2807
From:
Registered: Jun 2000
posted 04-11-2002 01:26 PM

That's what I thought too Wheeler, that they went out about the same time the optional engines did. A couple times people told me or I read that someone had a Diplomat with a 727.. At first I thought they just got the trannies mixed up, but then wondered why the service manuals cover them if they weren't available. Then someone told me that they were still an option in the fleet cars.
It's gotten me wondering how many cars I've seen have actually had them- the transmission is something I rarely think about when going through yards.
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How can I tell if a 904/999 is a lockup?

craig440cuda
Moparts Member
Posts: 336
From: hopkinsville ,Ky
Registered: Mar 2002
posted 07-03-2002 11:49 AM

How can I tell if a 904/999 is a lockup?I have one that came out of an 85 5th Avenue,would that be the desirable low gear trans?,And what tells me if its a lockup.the trans is on the ground,so I can see everything
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John Russo
Moparts Member
Posts: 1892
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-03-2002 11:55 AM

The '85 5th Ave should be lock-up as I own one! Take the converter off the input shaft. If the end of the input shaft is smooth, (no splines) for the first 3/4", then splines begin, it is a lock-up. The lock-up input shaft has 26 splines, and the standard has 27 splines (904's only). It will have the 2.74 low, 5 clutch front drum, 3.2 lever. If you have any other questions, let me know. John
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craig440cuda
Moparts Member
Posts: 336
From: hopkinsville ,Ky
Registered: Mar 2002
posted 07-03-2002 12:05 PM

Thanks for the quick reply.It is hollow(drilled?)it does have that smallsection of smooth before the splines.I guess it is a lockup.Where do I find a non-lockup???Can you swap input shafts to make it work???I need the low 1st gear,but I need non lockup.
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John Russo
Moparts Member
Posts: 1892
From: Portsmouth, VA, USA
Registered: Nov 1999
posted 07-03-2002 12:21 PM

You can do several different things. You can take the gear set out of this trans and put it in a non-lock-up trans. Or, you would have to get a non-lock-up pump, forward drum with input shaft (non-lock-up), a non-lock-up valvevbody. You have to be careful when swapping parts (except the gear set), as in '78+ there were changes in sealing ring diameters on the forward drum and pump reaction shaft support that will only allow those '78+ parts to be swapped or '77 down parts. Also, if you want the wide 5 clutch drum, you need to make sure you get a pump with a bevelled back, non-lock-up, and a forward drum with an 1-1/8" clutch hub to engage that extra clutch disc. The 4 clutch units had a 1" hub. So, swapping gears is easy, but the other parts have to be carefully matched so they will work together. John
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