904 to 727 swap compatability

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Shingar

Shingar

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I'm getting ready to replace my 904 trans with a 727 in preparation of upgrading my 273 to a 360....and my rear from 7.25 to 8.75 suregrip.

Spoke with a few vendors and another A-Body member. One vendor says the trans will swap over to the 727 without any modification to mounting. I know I will be looking at resizing my driveshaft,

The other vendor and A-Body member saya I will have to modify the trans mounting to accomodate the 727 as the 904 mounting is different. :banghead:

Again, I ask for your wisdom. I'm learning as I go....and can't seem to find an answer to this one.

I'd like to get that 727 ordered as the 360 should be ready in a matter of weeks.

Thanks in advance for your help.
 
Slip up under there and work it out. It will fit.

I recommend just building the 904. They are real easy. You can throw a rock and hit a build thread on them.
 
I was concerned that the 904 would not handle the extra TQ and HP that the new 360 I'm putting in will put out. Approx 400HP/400TQ. Am I wrong on that?
 
Shingar said:
I was concerned that the 904 would not handle the extra TQ and HP that the new 360 I'm putting in will put out. Approx 400HP/400TQ. Am I wrong on that?
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Definetly. Nothing special needed to do that. Look into it.
 
thesiren74 said:
I went through 2 904s and said forget it rebuilt the 727 no problems!
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Yes. This is what I've been hearing..... That's why I'm looking at swapping out to the 727 while I have the engine and rear replaced. Was curious if I'd need to modify my tunnel or mounts to replace the 904 with the 727? I know the driveshaft will require modification.
 
My buddy has 3 360 a bodies that run mid 10's in 3000 lb cars. A 70's 904 will hold up forever with good parts. The727 mith has been around for a long time. MY 904's have only broke once and it was because I didnt check th second gear band adjustment. All of the 904's that My friend has use a trans brake. No breaks in 3 years!
 

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Shingar said:
Yes. This is what I've been hearing..... That's why I'm looking at swapping out to the 727 while I have the engine and rear replaced. Was curious if I'd need to modify my tunnel or mounts to replace the 904 with the 727? I know the driveshaft will require modification.
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Go ask 70aarcuda, fishy68 and trailbeast what they think.

Oh, and My 360 is 400LB/TQ; with a 42RH behind it. Do the swap, you don't NEED to is all I'm saying.

The real killer is the TV valve; both transmission have them. It all comes down to having good line pressure and shift overlap.

Get a good, preferably 9.5" converter either way!!!
 
I ve swapped 727 for 904's before. It will fit, even the trans linkages are in the same spot for both transes. Just have to shorten the driveshaft.

Get under your car and start changing it, you will get it...
 
You don't need a 727 for strength. I run one because "that's what I got" "cheep." One thing.........if you have and are going to use the console shifter, make sure the new TF has the bolt holes underneath for the lower bracket.

Mount is the same.
 
Ok. Have the 904 in my Dart with a 400+ HP. No issues. If I remember correctly I did have some price issues with good flex plate and TQ converter. 904 > 727. Look in summit or jegs and price compare that aspect. My opinion build the 904 and Dave the trouble with mounts, driveshaft etc. if the racers build it and use them...what you are planning will be just fine. Plan to spend 900-1200 to have one built for you off a good core, less if you buy good parts and do it yourself. Btw, you ever pick up a 904 and then pick up a 727?
 
My racecar has 680 hp 904 handles it no problem. My AAR has 727 BUT if was just a 340 CUDA it would have a 904
 
thesiren74 said:
How much were those good parts? The 727 is tough the way it is.
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Only one special part...front drum 24 spring kit to keep the front clutches from dragging at higher rpm...for a stocker...not needed... cost 100 bucks...

stock clutches ...bands.....couple of upgraded parts like rear servo that cost 15 dollars...which i would replace in a 727 also... band strut...upgraded...but i replace those in 727 too...

build whatever makes you happy....
 
Shingar said:
I'm getting ready to replace my 904 trans with a 727 in preparation of upgrading my 273 to a 360....and my rear from 7.25 to 8.75 suregrip.

Spoke with a few vendors and another A-Body member. One vendor says the trans will swap over to the 727 without any modification to mounting. I know I will be looking at resizing my driveshaft,

The other vendor and A-Body member saya I will have to modify the trans mounting to accomodate the 727 as the 904 mounting is different. :banghead:

Again, I ask for your wisdom. I'm learning as I go....and can't seem to find an answer to this one.

I'd like to get that 727 ordered as the 360 should be ready in a matter of weeks.

Thanks in advance for your help.
Click to expand...

bellhousing are part of the trans....you need a small block 727....will need to cut driveshaft.....will need new torque converter......will needed either a weighted torque converter for a 360 or b&m 360 to 727 weighted flexplate....
 
Thanks for all the input.

I'm guessing I don't need to worry about crossmember? Same for 727 and 904?
 
I have a cross member if you need it. its just sitting in the garage. I will try to take pictures, maybe you can compare?
 
added bonus w/904 ...35lbs lighter and less hp loss due to lighter rotating mass
 
Thanks for all the input. I found a 727 core. Will be rebuilding it and putting a transgo shift kit in it.

I really appreciate all the knowledge and wisdom. Don't know what I'd do without this forum! Not many A-Body MOPAR experts in Oklahoma.

Thanks again!
 
One more added bonus for the 904, the low ratio first gear is extra cheap.

408 with indy 360-1 heads 700hp, trans brake, and yes a 904. Runs 9.90 at 135mph in good air. Shitty air 10.06 132mph.
 
A 904 built properly can handle 400/400 no problem. We run a '66 Cuda, 10.90sec. @ 119. I do mean PROPERLY! Stock parts work initially but will fail and when it does it won't be pretty. IMO, use the 904 with heavy duty parts.
 
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