318/8 Speed Swap

-
wish4hemi said:
1. A junkyard driveshaft is one option. Another option is an adapter flange yoke, Sonnax part number T35-ALFY-08. This gets you to a standard 1350 U-joint. From there, it's as easy as making a slip-joint driveshaft similar to how one would replace a ball & trunion joint (Early Valiant Barracuda Club - ball and trunion U-joint conversion)

2. The 8HP70 torque converter does not have an integrated ring gear. instead, there is an intermediate flexplate that goes between the crankshaft hub and the torque converter. By my measurements, the fix looks simple enough; just get a standard stick-shift flywheel for an LA motor, drill 6 holes in it, and bolt it to the 8HP70 torque converter. Picture attached of the torque converter. The 6 outer holes are threaded and would allow for a flywheel to be bolted to it.

3. Not sure on this one as my plan had this 8HP70 destined for a 3,740 lbs B-body.

4. You are correct. The tight gear ratios of the 8-speed would mean that you'll always be in the right gear at the right time. And you're able to jump on the laptop at any time to fine-tune shift points, firmness, etc.

View attachment 1715427965
Click to expand...

on 2. the Hemi uses a flexplate, and then this intermediate thing. Would the better option not be an LA flexplate with a ring gear? even if we had to machine a hub spacer.

Do you know the Spacing of the bolt pattern on the intermediate plate? I've found SB LA mopar to both the GM old school 3 bolt, and gm 4L pattern. Be rater lucky if one of them was the same.
LS-style 4L60E have a 11.066"
early GM are 11.5 and 10.75

Quick Time RM-947 Quick Time 130 Tooth Small Block MOPAR Flexplate

Thanks for the back and forth!!!
 
Last edited:
Johnny Mac said:
on 2. the Hemi uses a flexplate, and then this intermediate thing. Would the better option not be an LA flexplate with a ring gear? even if we had to machine a hub spacer.
Click to expand...

A flexplate would work too, although it isn't quite thick enough to make up the entire space between the crankshaft hub and the torque converter mounting plate. The hub spacer could solve that. Either way could work.

I'll have to look at my notes on the bolt pattern. I don't think it matched up with anything as I was hoping to use an adapter flexplate from Mopar small block to GM automatic transmission. But I don't think it was going to line up exactly.
 
I find it funny too that Chevy guys are using this transmission while Mopar guys are arguing about it.......and Mopar guys are using GM 200s, 700s, 400s, 350s, 4l60s and 4l80s BEFORE Mopar modern transmissions.
 
wish4hemi said:
A flexplate would work too, although it isn't quite thick enough to make up the entire space between the crankshaft hub and the torque converter mounting plate. The hub spacer could solve that. Either way could work.

I'll have to look at my notes on the bolt pattern. I don't think it matched up with anything as I was hoping to use an adapter flexplate from Mopar small block to GM automatic transmission. But I don't think it was going to line up exactly.
Click to expand...

I can machine up something like this in any length. I think we're getting closer!

upload_2019-11-24_16-11-54.png
 
RustyRatRod said:
I find it funny too that Chevy guys are using this transmission while Mopar guys are arguing about it.......and Mopar guys are using GM 200s, 700s, 400s, 350s, 4l60s and 4l80s BEFORE Mopar modern transmissions.
Click to expand...
I'm not arguing at all. I want to do it!! The Chevelle guy is a little more computer savvy then I, and made his own controller.
He used a complete bellhousing adapter. In our Case, a late model hemi or LA will bolt right to it. so we don't need a bellhousing adapter, but need to figure out the middle workings.

you wouldn't throw a 700 horse engine in front of a stock 318 converter, or one with the wrong balance. I think we're having a good brainstorm session!
 
Johnny Mac said:
I'm not arguing at all. I want to do it!! The Chevelle guy is a little more computer savvy then I, and made his own controller.
He used a complete bellhousing adapter. In our Case, a late model hemi or LA will bolt right to it. so we don't need a bellhousing adapter, but need to figure out the middle workings.

you wouldn't throw a 700 horse engine in front of a stock 318 converter, or one with the wrong balance. I think we're having a good brainstorm session!
Click to expand...

If you google 67 Chevelle with that transmission, you'll come up with the forum the guy's a member of where he detailed that swap.
 
Johnny Mac said:
This one? Yeah not a ton of info other than he did it.
Click to expand...

More on the driveshaft conversion. The Driveshaft Shop adapter has been mentioned on this forum before. Not sure if they have something that will mate to an 8HP70, but it gives you an idea of what the setup would look like. 392 in a 70 Duster
 
----o00o--'(_)'--o00o----
Watching...
Have a freshly built Reverse Valve Body Full Manual 727 bolted to our 6.1 Hemi but a 8HP70 is the new plan... Changing gears literally, Pun Intended. Break out the sawzall...
 
Last edited:
I'm in also on the powertour car. Spoke with sound German on the phone. Very professional and confident.
 
I'm already too far into my 727 setup at this point, but this is a great swap. I'd love to see some actual details from the Chevy guy about his controller.
 
Whoaaa, missed this thread!

SOOOOO SUBSCRIBED NOW!!!!!!
 
That thing is at least as big as a T56 magnum, I did that swap, going to be doing a lot to your torsion bar crossmember and tunnel for sure.

Would be cool to see this work.
 
8HP70 seems to be more attainable ($1000-$1500 price difference) opposed to the 8HP90 (call something a hellcat and price doubles)

most takeouts appear to be from 5.7 cars and trucks. obviously 2wd needed.
The Grail IMO, appears to be from a 6.4 car. It has a different torque converter than a 5.7 car. I can only assume higher stall than a 5.7 car. 6.4 makes more HP, has "bigger cam" etc.
RL261595AA / 68261595AA is the 6.4 challenger/ charger converter.
RL261258AA appears to be a 5.7 charger/challenger.

he 8speed has different gearing characteristics than say and old 727. It doesn't need a 4000 stall converter and 4.10 gears to get a 4000 lb car off the line.

I'm Hoping that the literal 1,000 lb difference doesn't hurt/affect the ability of an engine to idle in gear, w/o trying to grab. This would be the ultimate setback, but "chevelle guy" made no indication he swapped converters in his couple of videos.

Custom flexplate/flywheel is the biggest hurdle IMO to mating a SB, but its doable. I plan to document what i run into. flywheel is probably easiest way to do it, unless its TOO think, but I'd rather not hang 40 lbs of rotating mass onto my crankshaft. Custom flexplate with a spacer if needed is probably the route i'll go.

its perfect for a 5.7, or 6.4 swap. all OE stuff.
 
goldduster318 said:
That thing is at least as big as a T56 magnum, I did that swap, going to be doing a lot to your torsion bar crossmember and tunnel for sure.

Would be cool to see this work.
Click to expand...
Yes, the T-56 is a hoss, and in an A, the surgery is pretty intensive. My powertour car is a B-body...so i won't have all that data for an a...but can take measurements for those that will want to try it.
 
I,m interested been thinking about this for a while . think my 426 small block has the grun t to pull this off @2000rpm it's making 360 tq 4400 rpm it's making 560 tq , this 8 speed is just what it needs . prices you are talking about are way reasonable
 
Nat said:
I,m interested been thinking about this for a while . think my 426 small block has the grun t to pull this off @2000rpm it's making 360 tq 4400 rpm it's making 560 tq , this 8 speed is just what it needs . prices you are talking about are way reasonable
Click to expand...
Is that your peak torque? (560)
 
All of y'all worried about the stall needed for the 318 forget that this trans is used behind the 3.6 Pentastar V6 also. About the same torque as a 318.
 
'76 Feather Duster said:
All of y'all worried about the stall needed for the 318 forget that this trans is used behind the 3.6 Pentastar V6 also. About the same torque as a 318.
Click to expand...
That would have validity if the transmission, torque converter, and specs were the same from the v6 to the v8. And they are not. Completely different trans model. Also the torque converter in the 6.4 to the 5.7 also changes part numbers and size.
 
Johnny Mac said:
That would have validity if the transmission, torque converter, and specs were the same from the v6 to the v8. And they are not. Completely different trans model. Also the torque converter in the 6.4 to the 5.7 also changes part numbers and size.
Click to expand...

So use the V6 converter with the 318 and others with more powerful engines.
 
Found this. He makes it sound 'simple'. Maybe it is LOL

Zf 8hp70 mated to sbc

"
I honestly don't think you find a better trans for driving, its the same trans bmw (google 8p45r) uses in their race car only they run without a converter. that's my next project btw.
with the sbc at The Texas Mile i was shifting at 7k without lifting with 4.11 gears and it went over 150mph. it shifts in 150 ms, with a controller you can shift anyway you want as each shift is a clutch to clutch shift so you release one clutch and engage another. I first hit the engage clutch full pressure, wait 50 ms, then release the other clutch. it would bark the hoosier r4's all the way into 5th. honestly i'm afraid to try it with the ls, it makes 750rwhp. the one thing I don't like about it is the torque converter, no one offers anything for this trans. that's why I'm going to try direct drive and launch off of the beefiest clutch in the trans. it actually has a clutch pack designed for this, it's the same clutch that the bmw race car uses to launch."

..............and then he adds.........

after researching the crap out of it I just decided i had to have one. he only 'technical' part i'd say is getting a controller connected, i'm a software guy so i didn't mind taking the time to figure it out.
 
Johnny Mac said:
Is that your peak torque? (560)
Click to expand...
Yes it is 560 @4400 rpm . i hit the gas at 50mph without my cheater slicks and almost lost the car it started spinning so bad , never again with those BFG tires has lots of torque starting low I'll try to find the dyno sheet , 469 at 3000 rpm
 
Last edited:
You must log in or register to reply here.
-

Back
Top