Thinking about putting a later model automatic with OD behind my 1966 318 poly

[BartK]

My 1966 D 100 currently has a 318 poly with a 4 speed with a granny low and a 391 rear end. The speed limits on the freeways around where I live are 75 and most people run 80. With the current set up I have, it is hard to get 70 out of the old girl. I am sure someone has done the switch I am talking about, so I was hoping to get off easy and have someone tell me what I need to pull this off.

I am told, Yes you can. The early 518 non electric is good or the electric that you can wire a switch for the od. The poly block only has one bell housing bolt that won't line up. Most just leave it without. No big deal. You will have to make some cross member mods. I only installed one in a car that required floor mods, I assume that a truck will be easier. Being it's a truck the 518 is the same as a non od 727.

So guys, this is the first issue I am seeing. The 518 trans is the trans I was discussing with my transmission guy. The problem is that he claims the 518 would only work with the 6 bolt flywheel arrangement of the 318 engine, I have the 8 bolt version. Also, the 518 option requires driver input to switch on and off the overdrive feature. Failure to turn it off when not needed could potentially burn-up the transmission, according to my guy. Any comments on these issues?

I am open to any and all information and guidance!

[PwrWgnDrvr]

Change the rear axle ratio. Much easier!

[dodgeboykim]

I know people that have used the 89/90 727 based version overdrive transmissions behind 440 in a 52 Dodge Hot Rod pickup and 360 in a Lil Red. Worked for them.

[Txas2step]

viewtopic.php?f=34&t=25321&start=40
scroll down a few posts

[Hobcobble]

Change the rear axle ratio. Much easier!

I'll second that. Look for a 2.94 or 3.23 chunk.

John

[Jim100]

I too vote to at least try a gear swap. Open third members like mentioned by John are not very expensive and could be swapped in in a couple of hours.
Couple hundred bucks or less and some time.
jim

[marklein]

You should be able to get an 8 bolt flexplate for your engine. The non lockup version of the 518 is a one year only unit. Somewhere in 1990 they used it, rare to see one these days. The later 91-95 unit is a lockup version of the same unit. Od can be controlled with a simple switch, or you can buy a governer switch setup to control it. You'll need to cut out your crossmember and find one for the trans, shorten the driveshaft, find a transmission and converter, build cooler lines and get a trans cooler. I won't tell you not to do it, but for the cost involved and the gain, I would put gears in it. I have a 518 in my Fargo, but it was built that way and at 70, runs about 2400 rpm or so with 3.91 gears and 295-50 15's.

[wally426ci]

My 1966 D 100 currently has a 318 poly with a 4 speed with a granny low

Hey Bart, let me know if you pull the NP435 as I would be interested in it for my truck. Best of luck with any decision you move forward with. Thanks

[BartK]

Wally, I will keep you in mind if I decide to do the swap!

[my5thmopar]

I know people that have used the 89/90 727 based version overdrive transmissions behind 440 in a 52 Dodge Hot Rod pickup and 360 in a Lil Red. Worked for them.

Did you mean to type 440. I’ve never seen or heard about that unless maybe some sorts of special adapter. If I ever do another SB project I’ll do the OD upgrade with a 518-R42-R46 or similar. A lot of info on other sites about this.

[dodgeboykim]

I know people that have used the 89/90 727 based version overdrive transmissions behind 440 in a 52 Dodge Hot Rod pickup and 360 in a Lil Red. Worked for them.

Did you mean to type 440. I’ve never seen or heard about that unless maybe some sorts of special adapter. If I ever do another SB project I’ll do the OD upgrade with a 518-R42-R46 or similar. A lot of info on other sites about this.

My buddies 52 has an adapter to bolt the SB Trans to the 440. You can also use the Ultrabell( Think that's the name) to convert.

[dodgeboykim]

I know people that have used the 89/90 727 based version overdrive transmissions behind 440 in a 52 Dodge Hot Rod pickup and 360 in a Lil Red. Worked for them.

Did you mean to type 440. I’ve never seen or heard about that unless maybe some sorts of special adapter. If I ever do another SB project I’ll do the OD upgrade with a 518-R42-R46 or similar. A lot of info on other sites about this.

My buddies 52 has an adapter to bolt the SB Trans to the 440. You can also use the Ultrabell( Think that's the name) to convert.

https://www.google.com/url?sa=t&rct=j&q ... esypZmL7Vf

[BartK]

I know the 66 318 poly is a small block, but it is also a wide block. So for transmission purposes is the 318 poly considered a small block or a big block???

[PwrWgnDrvr]

I know the 66 318 poly is a small block, but it is also a wide block. So for transmission purposes is the 318 poly considered a small block or a big block???

"wideblock" is absolutely wrong! The poly and LA blocks are exactly the same! The only thing "wider" on a poly is the intake manifold due to a different angle on the intake valve side of the heads.
The proof of this is the fact that the 66 and earlier trucks with the poly 318 use the EXACT SAME BELL as the 67-68 trucks with the LA 318!
The 318 is a small block is a small block..period!

[Hobcobble]

I know the 66 318 poly is a small block, but it is also a wide block. So for transmission purposes is the 318 poly considered a small block or a big block???

It is a small block.

John

[Wildergarten]

It [318 Poly] is a small block.

Is the bell-housing bolt pattern the same as the LA series block?

[earlymopar]

It's not 100% identical as there is one bolt for the LA bell housing that is not used when mated to an A-series block (doesn't align with a tapped hole on the A series block).

- EM

[Wildergarten]

It's not 100% identical as there is one bolt for the LA bell housing that is not used when mated to an A-series block (doesn't align with a tapped hole on the A series block).

I take it people just leave it out? I'd bet there's no meat in the flange there to make drilling and tapping of much structural benefit.

[PwrWgnDrvr]

It's not 100% identical as there is one bolt for the LA bell housing that is not used when mated to an A-series block (doesn't align with a tapped hole on the A series block).
- EM

What do u mean by an "LA bell housing"?
Are u saying that there are 2 different hydro bells, one for 66 and earlier and a different one for 67/68?

[earlymopar]

Unless I misunderstood, the question was in reference to differences between the A and LA bell housing bolt patterns. There is one bolt hole on an LA bolt pattern that is off from the A series. The result is that when the LA application bell housing is used on an A series engine, one bolt is left out given it does not align with a tapped hole in the block. I'm running an LA series bell housing on my 64 Utiline / Poly and ran into this issue when mating-up the TK0-600. I don't know what a "hydro" bell housing is.

Thanks,

- EM