A518 O.D. Tranny Rebuild Question

Posted By: Tom Fox

A518 O.D. Tranny Rebuild Question - 10/26/12 08:59 PM

Guy's, I Have A Overdrive 518 Transmission Here That I Am Going To Rebuild To Replace My 833 With. I Have Never Built A 518, But Plenty Of 727's, Are They Pretty Much The Same Until I Get To The Overdrive Portion? Thanks, Tom.

Posted By: JohnRR

Re: A518 O.D. Tranny Rebuild Question - 10/26/12 10:11 PM

Yes the front of the trans is a 727 , the main difference is the rear drum support is also the apply piston support that allpies OD , the govenor is in the OD section behind the OD assembly.

You need a special tool to open up the OD section , best to take the OD section to a trans rebuilder and ask them to go thru it for you , rebuild the OD section to DIESEL specs if you have a high Torque/HP engine ...

Posted By: challengermike

Re: A518 O.D. Tranny Rebuild Question - 10/26/12 10:39 PM

Just make sure you take the od section as stated above to a trans shop to disassemble. There's a spring in there that is huge And would do you some big time damage if you pulled the snap ring out. At my shop we nickname it a chevette coil spring. Plus you would need a press and 2 special tools to properly assemble and disassemble it.

Posted By: 383man

Re: A518 O.D. Tranny Rebuild Question - 10/26/12 11:28 PM

There is also a shim that goes on the OD piston between the tranny and the OD unit. There are tools to make measurements to get the right thickness but most of the time (or most techs I know) just use the same one over. We had special tools at the dealer to measure it but just dont forget it if you use the same one over unless the shop you have do the OD unit gives you the thickness shim it should be. It looks like about a 4" washer with a 3-5/8" hole. Ron

Posted By: Dakota_Don

Re: A518 O.D. Tranny Rebuild Question - 10/26/12 11:50 PM

pretty much the same as the 727.. the OD unit is pretty simple as well.. you will need a press and and special tools to work on the OD unit or just take the OD unit to a trans shop but its simple, id replace the planetary s with one from a 618, 5 pinion, id add extra clutches as well id also add a trans go kit.. the directions will show u how to set up the OD unit clearances..

replace the pressure/gov.. trans ducer and the out put speed sensor as well..

Posted By: Tom Fox

Re: A518 O.D. Tranny Rebuild Question - 10/27/12 12:38 AM

Quote:

Yes the front of the trans is a 727 , the main difference is the rear drum support is also the apply piston support that allpies OD , the govenor is in the OD section behind the OD assembly.

You need a special tool to open up the OD section , best to take the OD section to a trans rebuilder and ask them to go thru it for you , rebuild the OD section to DIESEL specs if you have a high Torque/HP engine ...

Thats Good News. Yea I Had Already Heard About The Spring In The O.D. And Was Planning On Letting A Friend At Tranny Shop Do That Part. Anyone Have A Link Describing All Of The Improvement Mods To Help Trans Last Behind A H.P. Engine ? Thanks To All. Tom

Posted By: Dakota_Don

Re: A518 O.D. Tranny Rebuild Question - 10/28/12 06:41 PM

call a and a trans...... he can fill u in on the mods.. and parts.. if u have a press u can do the od spring....

Posted By: gtx6970

Re: A518 O.D. Tranny Rebuild Question - 10/28/12 06:51 PM

Quote:

call a and a trans...... he can fill u in on the mods.. and parts.. if u have a press u can do the od spring....

True a press is required, but so are the 2 special tools required to assemble the OD unit.

Posted By: feets

Re: A518 O.D. Tranny Rebuild Question - 10/30/12 03:34 PM

I have a cheap 20 ton press at home. Using it and a few pieces of steel made short work of that 800 lb OD spring.

Other than snap ring pliers I didn't need any special tools to go through my 518.

Posted By: JohnRR

Re: A518 O.D. Tranny Rebuild Question - 10/30/12 10:22 PM

The other tool aside from the press arbor that lets one get the snap ring pliers in and out is a splined shaft to keep the planetary in alingment so the output of trans will easily slide in , you can improvise that, I guess

Posted By: 383man

Re: A518 O.D. Tranny Rebuild Question - 11/01/12 08:31 PM

Quote:

The other tool aside from the press arbor that lets one get the snap ring pliers in and out is a splined shaft to keep the planetary in alingment so the output of trans will easily slide in , you can improvise that, I guess

John is so right as I forgot about that but you need the splined shaft to put down in the O/D unit to line up the splines. Believe me I have not seem anyone get it back on without using the tool. If you have a shop do it for you ask them to leave the splined alignment shaft in the O/D unit until you go to install it and that you will bring it back. Because I have seen some get the splines aligned but moving it around or even dropping or banging it around can throw the alignment of the splines off. I always left the tool in it until I was ready to bolt the O/D unit back on as you can pull it right out if its done right. Ron

Posted By: feets

Re: A518 O.D. Tranny Rebuild Question - 11/01/12 09:55 PM

I used the shaft to build the OD section first. After the pack was assembled I slid the shaft in and out then put the assembly to the side.
When the transmission was assembled I had no problems sliding the OD tail shaft into place.

Maybe I got lucky?

Posted By: 383man

Re: A518 O.D. Tranny Rebuild Question - 11/02/12 04:28 AM

Quote:

I used the shaft to build the OD section first. After the pack was assembled I slid the shaft in and out then put the assembly to the side.
When the transmission was assembled I had no problems sliding the OD tail shaft into place.

Maybe I got lucky?

No you just did it right. It seemed at the shop if it was on my bench and someone moved it and banged into anything it would throw them off and make it very hard to go on. You are right as long as no one moves it or anything it will work. But I always leave it in until I pick it up to put in on so I know its still lined up.

Ron