318/8 Speed Swap

[MopaR&D]

Keep in mind changing the shift scheduling of these newer electronic transmissions takes seconds and can be done on the fly. From what I remember driving my mom's 300C with the 3.6L and 8-speed, it won't go into 8th gear unless you're pretty much at freeway speeds although it is hard to tell what exact gear it's in without paying close attention. It also downshifts very quickly when any real load or throttle increase occurs. Not like a Torqueflite that's intended to get to top gear and stay there most of the time.

 

[DionR]

Tripped over a comment on a Challenger forum that some people get over-rev codes with a 3.90 rear gear and an A8 because it can't shift fast enough in the lower gears. Just an FYI, doesn't mean everyone that does that has an issue, but sounds like some do.

I haven't selected tires yet though I do like the "steelies" with dog dish caps. I was thinking of 275/60-15 or 295/50-15 if I stay with those rims. 275/60 is 28"D and the 295/50 is 26.6"D.

The Challenger 245/45R20 is about 28.7" tall so you would be shorter with either tire. So your 2.76 would be like running a 2.83 or 2.97 in a Challenger, depending on which tire.

BTW, the 845RE (A8) V6 Challengers got a 2.62 with the performance option being a 3.08. R/T's and Scat Packs Challengers got a 3.08 or 3.09 depending on if the axle was open or had a limited slip. Hellcat's only come with a 2.62 rear gear, no 3.0x option.

 

[roadrunninMark]

Sound German has a gear indicator display so you can see what gear you are in. Possibly, Dakota Digital dash may have that too? Not sure...

Dion..yes I think the 2.76 puts me right where I want to be, with your info backing it up. The V6 weighs in at 3886 lb, so I am still about 500 lbs lighter. Even though the trans is heavier, along with the driveshaft, I will be losing some weight with aluminum heads, intake, and radiator. I also will be using fiberglass bumpers on both ends. I changed the front drums to disc, maybe a few pounds of savings there. I am also thinking of going rear disc eventually. I will probably add a little weight though with the bigger wheels/tires, larger T bars and anti sway bars.... so maybe it all will be a wash.

V6 shows about 300hp 268TQ so I will be quite a bit higher on the power too. EDITED ** 1st gear is 4.71 for the V8 version too. **

 

[4.7Light]

My car has a 2.76 gear in it now, 8 3/4. You would have to find used for that gear. I need a sure grip still. From what I understand the C bodies had 2.76 sure grips. Also thinking since my car is probably 900 lbs or so lighter than a new challenger, the 2.76 might be just right. I could step up to a 2.94 too, if it "lugs" too much. I am estimating my engine putting out around 400hp, so I am in the window of a stock 5.7 hemi. I haven't selected tires yet though I do like the "steelies" with dog dish caps. I was thinking of 275/60-15 or 295/50-15 if I stay with those rims. 275/60 is 28"D and the 295/50 is 26.6"D.

I don't know how much it was raised but I told the shop I am using a shaker hood so the engine has to be in the stock location. They assured me it is. I think they took the conservative route and just cut a lot to be sure. I wasn't planning on this as I wanted to use the stock console but that isn't going to happen now. I am fitting in the new challenger console, which solves the shifter issue I was going to have.

I have a 2.94 right now thinking I may be able to stick with it little more RPM but that would still be better than current rpms with 727.

 

[DionR]

I have a 2.94 right now thinking I may be able to stick with it little more RPM but that would still be better than current rpms with 727.

Are you thinking about the 8HP70 swap again? Thought you walked away from that path.

 

[4.7Light]

Are you thinking about the 8HP70 swap again? Thought you walked away from that path.

Im on the fence still I think the TKX may be fine but I like the idea of the auto and driving it. I want to drive to KC or say OKC and thats 4 hours. Thinking this would maybe be slightly more enjoyable, we have owned 5 cars with the 8 speed my Ram and Grand Cherokee have it. Very reliable is the key here. I read the TKX can be an issue its smaller and the t56 is maybe out of my price range.

 

[roadrunninMark]

2.94 is a great gear too, a little more responsive than the 2.76.

 

['Cuda_ragtop]

Here is a calculator that I used for my build project.
Drag Times Gear Ratios Calculator, MPH, Top Speed 275/40R17, 3.23
This link has my wheel/tire combo with 3.23 rear gear and 8HP70 transmission.
It calculates Speed and RPM for each gear through my set red-line of 6000 RPM.
Plug in your own numbers to get the results for your setup.

May not be my final setup but looks like a good starting point.
This is with a 6.1 G3 Hemi in a 69 Barracuda Fastback. Might go with a little taller tire but this is what we have on the car now. Car is not road ready yet. Got the engine and transmission installed a couple weeks ago but still a lot more to do.

 

[DionR]

Here is a calculator that I used for my build project.
Drag Times Gear Ratios Calculator, MPH, Top Speed 275/40R17, 3.23
This link has my wheel/tire combo with 3.23 rear gear and 8HP70 transmission.
It calculates Speed and RPM for each gear through my set red-line of 6000 RPM.
Plug in your own numbers to get the results for your setup.

May not be my final setup but looks like a good starting point.
This is with a 6.1 G3 Hemi in a 69 Barracuda Fastback. Might go with a little taller tire but this is what we have on the car now. Car is not road ready yet. Got the engine and transmission installed a couple weeks ago but still a lot more to do.


View attachment 1716105458

I am dying to see that car on the road. Get'er done and road trip it over to this side of the state!

Curious to see how the combination works, too. Nice data.

 

[4.7Light]

Here is a calculator that I used for my build project.
Drag Times Gear Ratios Calculator, MPH, Top Speed 275/40R17, 3.23
This link has my wheel/tire combo with 3.23 rear gear and 8HP70 transmission.
It calculates Speed and RPM for each gear through my set red-line of 6000 RPM.
Plug in your own numbers to get the results for your setup.

May not be my final setup but looks like a good starting point.
This is with a 6.1 G3 Hemi in a 69 Barracuda Fastback. Might go with a little taller tire but this is what we have on the car now. Car is not road ready yet. Got the engine and transmission installed a couple weeks ago but still a lot more to do.


View attachment 1716105458

Yours will be one hell of a car nice work! Thanks for calculator this was the deciding factor. TPS sensor on my Holley 4160 and a tach wire , SGA controller and 8hp shifter. Harness I will see if I can nab with transmission. Looks like that may make this easier. Going in a LA 360 I think this will make this very happy combo in the gears cruising or jumping on it. Need to order adapter as well understand that's a complete kit for bolt up JVX.

 

[dbc105]

Did anyone get a copy of the sketch and Gerber files for Chevelleguy's controller? That stuff would sure be handy.

 

[TurboGLH]

Did anyone get a copy of the sketch and Gerber files for Chevelleguy's controller? That stuff would sure be handy.

No, I reached out and we talked a bit, but he stopped coming back to the forums.

I also spoke with Russell at s
Sound German about directly controlling the servos and his opinion is that you're losing a lot of the benefits of the TCU programing, which monitors clutch pack health and makes adjustments to engagement speed and pressure to help improve life.

 

[DNasty777]

The pentastar v6 has the same bellhousing pattern as the small blocks and gen 3 hemis, correct? I can get an 845re for a couple hundred bucks locally, I might be inclined to do some tinkering.

 

[DionR]

The pentastar v6 has the same bellhousing pattern as the small blocks and gen 3 hemis, correct? I can get an 845re for a couple hundred bucks locally, I might be inclined to do some tinkering.

@myduster360 did a Pentastar/5 speed swap into a Dart and they are not the same.

72 Dart Swinger 3.6L Pentastar +T5

I picked up this Swinger(318/auto) roller a few months ago down in Southern Mo. It was exactly what I was looking for. New 1/4 panels, floors and paint & ready to be reassembled the way I wanted. Plus at just $2500 I couldn't pass it up The interior is bare but I have most all the pieces as...

www.forabodiesonly.com

 

[DNasty777]

@myduster360 did a Pentastar/5 speed swap into a Dart and they are not the same.

http://[URL]https://www.forabodieso...ger-3-6l-pentastar-t5.361683/#post-1971409535

[/URL]

Dang, there goes that source of cheap trans.

 

[DionR]

Any progress on any of this?

I tripped over an outfit in Australia that is outfitting the 8HP's with a virtual clutch that locks up the TC and engages or disengages internal clutches progressively just like a real clutch. Looks pretty cool.

Also found out that the SGE kit allows for a Sport and Track mode shift schedule with the flip of a switch. That was new info to me.

Really makes me want to put an 8HP70 behind my 5.7 (or even better, a 6.4) and set it up for a drag and drive event. I could even see leaving the MDS in it and use an OEM PCM so that sport/track mode could disable it, but I could cruise the highway with it in use. Only real hang up is how to get cruise control to work through the PCM.

 

[Dantra]

Any progress on any of this?

I tripped over an outfit in Australia that is outfitting the 8HP's with a virtual clutch that locks up the TC and engages or disengages internal clutches progressively just like a real clutch. Looks pretty cool.

Also found out that the SGE kit allows for a Sport and Track mode shift schedule with the flip of a switch. That was new info to me.

Really makes me want to put an 8HP70 behind my 5.7 (or even better, a 6.4) and set it up for a drag and drive event. I could even see leaving the MDS in it and use an OEM PCM so that sport/track mode could disable it, but I could cruise the highway with it in use. Only real hang up is how to get cruise control to work through the PCM.

Believe me, they are worth it for so many reasons, especially behind a 5.7.. stays in the sweet spot longer, better fuel economy and something that I really see anyone talk about is braking. I noticed a huge change in deceleration with my A100. These things just downshift and slow down so well.. especially if you command it. If i tap the accelerator as I go to slow down, that commands it to drop a gear and I am able to come to a stop, quite a bit faster. sometimes it can be pretty drastic, so I only do it as needed. But besides that, the normal downshift is smooth and it downshifts several times as you come to a stop. It's pretty sweet.

I'm not putting one behind my 392 swap this year because it will blow my winter project timeline and budget outta the water. I'm just afraid that the floor cutting, tunnel building, replacing the (new) carpet, finding bucket seats (in Buckskin) and a console that needs to be modded will push me beyond the April timeline that I like to go by.. not to mention the budget!. I try to be done in April with stuff because I want to drive in May. I'll be patient this summer and keep an eye out for things I need for next winters project.. or maybe the year after that. No rush. I'm trying to enjoy my builds and not let them stress me out or turn into 5 year project that just sits.

 

[DionR]

I'm not putting one behind my 392 swap this year because it will blow my winter project timeline and budget outta the water. I'm just afraid that the floor cutting, tunnel building, replacing the (new) carpet, finding bucket seats (in Buckskin) and a console that needs to be modded will push me beyond the April timeline that I like to go by.. not to mention the budget!. I try to be done in April with stuff because I want to drive in May. I'll be patient this summer and keep an eye out for things I need for next winters project.. or maybe the year after that. No rush. I'm trying to enjoy my builds and not let them stress me out or turn into 5 year project that just sits.

I've adopted the same plan; limit mods during the winter to what I can get done before nice weather and keep it off jackstands during the summer. This winter was suppose to be the winter of the 5.7/T56 swap but I've changed directions and plan to put that combination in a '73 Duster that I recently acquired instead. And because of the new vehicle, I don't feel the need (nor have the space) to get it done during the winter.

My biggest struggle now is trying to decide if I should be doing an 8A instead of the 6M.

 

[4.7Light]

Well I guess I'm going first I ordered everything I read up all the wiring. Based off what I saw If I can wire the whole car I can do this. I have seen in the LARB 8HP70 Facebook page they are doing this successfully with LA engines no cranks sensor. So I have picked up my transmission and I am formulating a major project now.

 

[DionR]

Well I guess I'm going first I ordered everything I read up all the wiring. Based off what I saw If I can wire the whole car I can do this. I have seen in the LARB 8HP70 Facebook page they are doing this successfully with LA engines no cranks sensor. So I have picked up my transmission and I am formulating a major project now.

View attachment 1716213680

View attachment 1716213681

Cool! How soon do you plan to have it done?

 

[Dartswinger70]

Pretty sad a Chevy guy has an 8hp70 8 speed and mopar guys just argue about how it can't work mopar guys need to step it up

Uncle Tony's MI 318 is a Ford and Chevy guy doing all the R & D to get a 318 to put out 300 Horse. I agree about stepping up..

 

[4.7Light]

Cool! How soon do you plan to have it done?

Waiting for the parts before Oklahoma goes blazing outside lol!

 

[4.7Light]

Cool! How soon do you plan to have it done?

Parts ordered I should have pictures coming as I progress. Hopefully have controller and adapter next couple weeks.

 

[DNasty777]

I'll also be doing an 8HP70 swap, picking mine up from the junkyard tomorrow. It's going on the back of a 360 magnum, and I'll be getting a flexplate from JVX racing. Still deciding how I'm going to control it but I'm leaning towards the Turbo Lamik controller.

 

[DionR]

I'll also be doing an 8HP70 swap, picking mine up from the junkyard tomorrow. It's going on the back of a 360 magnum, and I'll be getting a flexplate from JVX racing. Still deciding how I'm going to control it but I'm leaning towards the Turbo Lamik controller.

Are you going to do the clutch emulator setup on it?