a518/a727 torque converter interchange

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derrangedgadgeteer

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Simple question, do they interchange? Lockup for lockup. It's apparently rather close to impossible to find stall converters for the 518 under $400, but Mopar sells just the one I need for the 727 for a reasonable sum of $230.

If the 518's really just a 727 with an overdrive gear, I wouldn't expect the converter to be different. But I've not found information one way or the other. :banghead:
 
a regular 727 converter will not fit a 518 which uses a lock up conveter...the splines are difference...

727...24 splines
518...23 splines..


but are you saying your 727 is a lockup?
 
70aarcuda said:
a regular 727 converter will not fit a 518 which uses a lock up conveter...the splines are difference...

727...24 splines
518...23 splines..


but are you saying your 727 is a lockup?
Click to expand...

There were a large number of 727's made after 1976 that were indeed lockup, and mopar performance sells a lockup converter with a 2300 stall for the 727.

Now then the question I'll have to answer, is the lockup 727 23 spline like the 518 or 24 spline like the non-lockup 727...

I'm going to go do some more looking, are you positive the 518 has a 23 spline input shaft?
 
okay, found info. Allpar Says:

A-727 transmissions from their inception until 1966 have 19 splines on the input shaft. Non-lockup 727 transmissions from 1967 onward have 24 splines. Lockup 727 transmissions that debuted in 1978 had 23 splines.
Click to expand...

So, I think I'll give an overdrive with a lockup 727 converter a try.
 
oldkimmer said:
...........I do know that the non lock ups interchange..............kim...........
Click to expand...
Can you chissel that in stone? The reason I'm asking is because I can't get an answer from companies that sell converters. They want to charge more for the A-518 verter, of course.
 
Im basing this off a th-350 gm trans so may be way different on an auto mopa. but a lockup converter WILL fit a non-lockup trans but it does not work right. Generally wont catch gears and eventually ruin the transmission.
 
If they don't have an answer it sounds like they don't know and aren't the people to deal with? I have not personally tried to install a 727 converter in a 518 but I know the input shaft, stator splines and front pump lugs are the same. What else can be different? Call John Cope at Cope Racing Trans. He's a straight shooter and will know if there's any difference and not try to sell you something you don't need. 219-374-0100 is his number. John is also a member here on the board.
 
Lockup and non-lockup Mopar converters WILL NOT interchange. The input shaft is different. One will not fit on the other.

As posted above, if your 518 has a 23 spline input shaft it is a lockup transmission, if it has 24 splines it is a non-lockup transmission (there 518 was available both ways, all 500's were lockup).

Cope, PTC, or SMR Transmissions should be able to set you up with what you need.
 
.............727 lock ups were manual........no solonoids.....518s lock ups had solonoids... there is non lock up 518s.......kim........
 
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