904 Transmission for 79 360 motor

Posted By: CudaDave7071

904 Transmission for 79 360 motor - 03/19/12 06:47 PM

I've got a 79 360 engine with a 904 transmission. The 904 trans was from an A-Body 318.

Question: are there differences between torque converters for a 904 for the 318 and 360 motors?

I've got some motor vibration issues (longer story) but this answer might help me out.

Thanks!

Posted By: mod5v

Re: 904 Transmission for 79 360 motor - 03/19/12 07:03 PM

Yes 360 has balance weights on it. easy fix would be a B&M flexplate for the 360.

Posted By: roe

Re: 904 Transmission for 79 360 motor - 03/19/12 07:09 PM

Yes there is a difference. I had to do this when I put my LA 360 in my satellite with a 904. In order to run your 904 with the 318's nuetral balance converter behind your 360 you need to pick up a weighted flexplate from B&M or an equivalent. The one I picked up had 727 & 904 pattern on it so don't be scared away from one that's has both if you come across it.

The second option is to use your nuetral balanced flexplate and a weighted converter with the 904.

I chose the aftermarket flexplate and i'm glad I did. It's much stronger than a stock flexplate and I never had to remove the trans or torque converter from the car during the swap, and I didn't lose a drop of fluid either.

Posted By: Paul_Fancsali

Re: 904 Transmission for 79 360 motor - 03/19/12 08:33 PM

Only problem is a stock 904 does not live long behind a built 360 even a modest built one.

Posted By: 75DART440

Re: 904 Transmission for 79 360 motor - 03/20/12 12:16 AM

Yet another option: Grab a used 904/360 converter, even if it's NFG. Flexplate will only bolt on one way. Using the flexplate laid in place on the donor converter, mark location of weights. Measure carefully. Knock weights off of donor converter. Place your converter face down on a bucket, line up your marked flexplate, and using your measurements you now know where the weights need to be. Weld 'em on!

Kinda meatball surgery, but I had a friend with a 360/904 70 Dart that was done this way, and it went 75,000 miles without a problem. Too many donuts, burn outs, and brake torquing finally killed the 904. We did a second converter for a junkyard trans so he could sell the car. Next owner ran it a year and totalled it.

Posted By: MoparforLife

Re: 904 Transmission for 79 360 motor - 03/20/12 01:20 AM

Quote:

Yet another option: Grab a used 904/360 converter, even if it's NFG. Flexplate will only bolt on one way. Using the flexplate laid in place on the donor converter, mark location of weights. Measure carefully. Knock weights off of donor converter. Place your converter face down on a bucket, line up your marked flexplate, and using your measurements you now know where the weights need to be. Weld 'em on! Kinda meatball surgery, but I had a friend with a 360/904 70 Dart that was done this way, and it went 75,000 miles without a problem. Too many donuts, burn outs, and brake torquing finally killed the 904. We did a second converter for a junkyard trans so he could sell the car. Next owner ran it a year and totalled it.

Don't that weld up thing to many converters. Not a major surgery thing and is a money saving thing. Ran 11's at the strip for years with a converter I did this way.

Posted By: Evil Spirit

Re: 904 Transmission for 79 360 motor - 03/20/12 04:43 AM

Quote:

Only problem is a stock 904 does not live long behind a built 360 even a modest built one.

A 904 With stock internals will last a long time with a proper valve body installed as long as it was healthy to start with. I've built 904's out of my leftover "junk" - 6 cyl 3 disc forward and direct drums, aluminum planetary sets, etc. and had them last behind 350-400hp engines as long as a good shift kit was used, which you would probably also do to a 727. The same things that kill a 904 will kill a 727 - improper kickdown linkage or adjustment being the worst culprit. And for every cracked 904 converter hub that I've changed I've probably changed 2 broken 727 rear bands.

Posted By: 70AARcuda

Re: 904 Transmission for 79 360 motor - 03/20/12 05:11 AM

Quote:

Only problem is a stock 904 does not live long behind a built 360 even a modest built one.

if you are having problems with a 904 lasting behind a modest build 360...you need to find someone else to build your trans....

Posted By: 5thAve

Re: 904 Transmission for 79 360 motor - 03/20/12 06:57 AM

I've had my share of 904s die behind 360s. I quit gambling and went 727.

Posted By: goldmember

Re: 904 Transmission for 79 360 motor - 03/20/12 07:24 AM

Quote:

Quote:

Only problem is a stock 904 does not live long behind a built 360 even a modest built one.

if you are having problems with a 904 lasting behind a modest build 360...you need to find someone else to build your trans....

Right on! I get a

out of the put a 727 in it suggestions for most street and street strip guys.

Posted By: JohnRR

Re: 904 Transmission for 79 360 motor - 03/20/12 01:08 PM

Quote:

Quote:

Only problem is a stock 904 does not live long behind a built 360 even a modest built one.

if you are having problems with a 904 lasting behind a modest build 360...you need to find someone else to build your trans....

You are ASSuMEing some of these people are having their 904's gone thru ...

Posted By: RapidRobert

Re: 904 Transmission for 79 360 motor - 03/20/12 04:00 PM

Quote:

if you are having problems with a 904 lasting behind a modest build 360...you need to find someone else to build your trans.

We've beat em to death w stock rebuild parts & still no probs. less reciprocating/rotating weight less overall weight

Posted By: Paul_Fancsali

Re: 904 Transmission for 79 360 motor - 03/20/12 08:48 PM

A good set of tires and fairly heathy engine and can you say KABOOM! two different 904s by two different trans shops none cheap and thats what. I will stick with my current 727 combo that has 900 passes and cost the same amount to build with aftermarket parts

Posted By: 70AARcuda

Re: 904 Transmission for 79 360 motor - 03/20/12 11:13 PM

Quote:

A good set of tires and fairly heathy engine and can you say KABOOM! two different 904s by two different trans shops none cheap and thats what. I will stick with my current 727 combo that has 900 passes and cost the same amount to build with aftermarket parts

well..hear ya go again...LOL

I got 3 904s with transbrakes installed..one is going 7 seasons on it..another has 5 ..and the newest one has 1 season..and they are very high tech trans..I rebuilt them..LOL...probably got 300 bucks worth of parts in them outside the transbrake.

one car has got 10.69 (7 seasons)...the slowest is 11.18 (1 season) .out west in Vegas,,,tire size range from 14 x 32 to 10 x 29 slicks.

need to find someone who knows what they are doing..

Posted By: Locomotion

Re: 904 Transmission for 79 360 motor - 03/20/12 11:49 PM

I burned up 3 stock 727's behing a basically stock 340 when I first started driving. A shift kit made a world of difference and a good valve body was be better.

I've run a 904 behind my 360 Dart Sport. JW Transmissions builds them with nothing I'd consider trick -

* Manual reverse valve body
* 4.2 kickdown lever
* I believe the "red" clutches, not sure about bands.
* Amsoil Supershift trans fluid
* Trans cooler and deep pan
* Converter flashes over 5,000

I'm pretty sure the rest are OEM parts except with some oiling/bearing tweaks.

I weigh 3,540 lbs +, have run 11.22 @ 116 with 1.47 60' times. On several occasions after several years of running, my trans builder said to keep doing whatever I'm doing as far as running it, adjustments, fluids, servicing, etc. The only time I remember that a 904 went "BOOM" on me was when a rear u-joint let go at the 1/8 mile mark. The result ended up with a bent converter and chunks taken out of the block. But it wasn't the transmission's fault. I got a steel billet rear end yoke and solid Spicer 7260 joints that are still in after many years.

Get the proper B&M flexplate which will solve the converter balance problem and it's a heck of a lot more durable than the OEM plate.

Posted By: GO_Fish

Re: 904 Transmission for 79 360 motor - 03/21/12 12:11 AM

My 904 with a B&M flex plate, 9.5" Dynamics converter and Cheetah full auto valve body (remainder stock internals) is just fine behind my mild 360. 13.59 at 98.72mph, trans is happy.

Posted By: rustbuckett68

Re: 904 Transmission for 79 360 motor - 03/21/12 02:26 AM

I ran a rebuilt 76 998 behind my stock (with a TQ carb and intake)76 360 in my 74 Cuda with no problems. Second gear rubber every time, my GM tranny tech buddy could not compehend how hard it shifted. Car ran an 14.97 with a 2 BBL cam. Had to answer a lot of questions. Then the car ran away from home!

Posted By: slantzilla

Re: 904 Transmission for 79 360 motor - 03/21/12 02:33 AM

Funny thing is that in the 'Race' section they will tell you a 727 is junk and you need a Powerglide.

One thing a good 904 will never do that a 727 will is explode the front drum.

Posted By: Evil Spirit

Re: 904 Transmission for 79 360 motor - 03/21/12 03:03 AM

Quote:

Funny thing is that in the 'Race' section they will tell you a 727 is junk and you need a Powerglide.

One thing a good 904 will never do that a 727 will is explode the front drum.

I stand beside my 904's, because I'll never sit on top of a 727...