Silver Sport Transmissions A41 4-speed Overdrive Question

[Rustymuscle]

Hey guys! I'm Kevin Shaw, Editor-in-Chief of Mopar Connection Magazine (www.moparconnectionmagazine.com). We do a lot of work with Silver Sport Transmissions and they showed particular interest in adapting their "A41" 4-speed automatic overdrive transmission kit for our '70 Plymouth Fury III convertible project car.

But as is with all things, they're curious if anyone else in the C-body community would be interested in updating their C-body with the similar kit. The A41 begins with a 4L60E or 4L65E overdrive transmission that is fitted with a Chrysler bellhousing (SB or B/RB) and a modified tail cone. It can be adapted to be manually shifted or use a TCM.

They currently have kits for A, B and E-bodies and they wanted to to branch out into C-bodies, so I'm here to help gauge public interest. Obviously, this isn't for everyone (particularly those who are restoring their builds per factory) but for those looking to modify their Mopars.

I'll try to answer as many questions as I can, but I am NOT an employee of SST, just a friendly messenger.

 

[Mr onetwo]

I couldn't find a price on the exact B body kit , however Butler Performance has a Pontiac kit that appears to be the same for for $5149. Pretty expensive on the surface, but more research needs to be done on the pros and cons of this particular transmission.Silver Sports stuff is top notch.Just for me personally, I think I would go with a nicely built 727 and a Gear Vendors unit.Keep in mind my Fury is a 318 car and I hate driving on the interstate

 

[1970FuryConv]

$5000 is way outside my needs. I drive my C body cars 1000 to 2000 miles per year. There is no reason to spend all that money for an extra gear. I rebuilt the 727 that is behind my 440. It's been a reliable and excellent transmission.

 

[70bigblockdodge]

Overdrive is never a bad idea IMO. Hard sell to C body guys because most don't go over a 3.23 rear gear. With a large diameter 15" tire around 3k at 75-80 mph. The lock up is good but the .83 ratio is better in the small block pick ups and vans it was originally designed for. It would give a option as a kit. Almost everything is the same with exception of trans crossmember and driveshaft lengths.

 

[Rustymuscle]

The kit's price range varies on the performance level that you need. I built one for my 10-second '69 Charger that retailed for a little over $8K but that also had the TCM controller box and harness (admittedly, that was overkill for what I needed).

But yeah, they'll be around the $5K mark for everything you need to make the swap.

You're right about the C-bodies all coming with high ratio gearing. Few are rolling on anything above 3.55 in my experience.

Again, this would be for the guy building something really unique who could benefit from a .68 overdrive.

 

[HOT FURY]

Hey guys! I'm Kevin Shaw, Editor-in-Chief of Mopar Connection Magazine (www.moparconnectionmagazine.com). We do a lot of work with Silver Sport Transmissions and they showed particular interest in adapting their "A41" 4-speed automatic overdrive transmission kit for our '70 Plymouth Fury III convertible project car.

But as is with all things, they're curious if anyone else in the C-body community would be interested in updating their C-body with the similar kit. The A41 begins with a 4L60E or 4L65E overdrive transmission that is fitted with a Chrysler bellhousing (SB or B/RB) and a modified tail cone. It can be adapted to be manually shifted or use a TCM.

They currently have kits for A, B and E-bodies and they wanted to to branch out into C-bodies, so I'm here to help gauge public interest. Obviously, this isn't for everyone (particularly those who are restoring their builds per factory) but for those looking to modify their Mopars.

I'll try to answer as many questions as I can, but I am NOT an employee of SST, just a friendly messenger.

View attachment 560620

I would be interested in discussing this for my build. Would be fun to pair it behind the stroker I'm building for my 66 sport fury

 

[furious70]

Got an a500 behind my turbocharged 383. Maybe I need the big guy so I stop driving through the converter...
Are they giving it away if we hand our car over?

 

[Rustymuscle]

Guys, calm down. They're just wanting to gauge potential customer interest. They haven't even gotten approval to start developing parts yet.

 

[HOT FURY]

Unfortunately I reached out to them regarding this and received the following reply from their senior sales rep and tech mgr:

We don't have this one on the radar as we do not get many requests. I can sell you an auto or manual Overdrive and a good amount of components to hook up behind your engine but ultimately fitment would be up to you.

 

[fury fan]

I would be really interested in this kit, it's got a lot of benefits - but the cost isn't in my gameplan right now:

Benefits:
Bolt-on conversion BH vs some adapter plate stuff and modifying a trans housing. (like the A518 onto a bigblock).
The 4L60-70 can be built to be pretty stout, and for many of us would be durable with just a mild near-stock rebuild.

The 3.06 first gear ratio changes a 3.23 into the equivalent of a 4.03 axle ratio (vs a 727).
The OD ratio is .69 -- the .83 mentioned above likely refers to teh Gear Vendors, which is .83.
.69 turns the 3.23 into a 2.22 ratio in OD. Many people might squawk at that being too low, and while not ideal, Chrysler did have 2.45 ratios commonly in the 70s, and some even at 2.2 (my family owned such a car). So could be usable unless a non-stock cam.
So maybe a 3.55 re-gear is more appropriate => becomes 2.45.

IIRC the transmission controllers allow paddle-shifting, or at least you can have switches to manually-control OD and LU.
And of course the controller allows to electronically tune the trans to your desired personality.
And being based on the 4L6-series, the trans is smaller and easier to install.

But when I looked into all of this stuff several years ago, it all added up - there were some cost-saving routes (like a manual VB in a junkyard 4L60E ) but still wasn't cheap.

What it all boils down to - adding an OD trans, for most of us, is a $3-5000 prospect.
Whether it's a Passon OD, a Tremec 5-6 speed, this A-41, an A518 with adapters, or a Gear Vendors - all of them are a major spending decision.

I will propose, though, that improved gear ratios and shifting personality will add a HUGE performance benefit - but most guys will 'automatically' spend that money on engine work instead.

But dropping $5000 on a single upgrade isn't my style.
If Silver State would sell the bellhousings and modified tailshaft housing separate from the kit I might buy just for potential future use.
I can absorb that cost, then start looking for the right 4L70 to cross my path, and try to piece it together over time.

 

[furious70]

I would agree OD never pays for itself in mpg savings or such. If you're building a car from scratch it's not as bad as replacing a working unit. You have to weigh the upgraded ability of the car. Ridiculous flexibility in driving behavior with OD because of the low start gear and OD.
Way way more fun than a 727 and 3.23's as the typical compromise. Just gotta pay to play.

 

[70bigblockdodge]

The OD ratio is .69 -- the .83 mentioned above likely refers to teh Gear Vendors, which is .83.

Hmmm, my bad, I guess it is .69 or .70 depending on which page you click on. Not sure how I got .83 in my head. That will make it better. Would be nice if they would just sell the bellhousing and the flex plate.

 

[Mbaird]

Problem is that a 46rh will fit and cost much less even if you need an adapter for a bigblock. I just picked one up for $200. I will drop another $1000 on it for upgrades and performance rebuild but the total will be far less then 5k. 3.55s with the .69 OD brings you to a 2.55 final drive . That’s important out here in the west where you need to go 80+ or get run over ! Really annoying !

 

[3175375]

I believe that the 4L60 is a less than desirable transmission (I read junk). I believe that the 4L80 is the GM transmission to seek.
But why do this at all?

If someone was a traveling salesman, driving all over, this may have merit, if it was a 4L80.

Pass for myself and ceveat emptor for all considering…

 

[Mbaird]

I actually put around 15,000 miles on my 68 Barracuda in the last year and a half. And am forced to use the freeway due to congestion and poorly timed traffic lights on city/county roads. I have a set of 2.76s in it now and still teaching around 3k at freeway speeds ( and still getting passed !). Riding my dual sport is death defying on the interstate !

 

[fury fan]

The 4L80 is much bigger and stronger, but I've not read anythign about the 4L60-65-4L70 being junk.
If one used a '4L60', they would want to get the 4L70 version, which has more pinions in the planetaries, more clutch disc and other related improvements, and then see what upgrades make sense.
As for fit, the 518/46RH is a 727 with an OD added on, so it's much larger at the rear, often requiring tunnel mods (at least in the smaller cars).
The 4L60 is sized/shaped more like a typical trans, 4L80 is similar shape but that one is reportedly very bulky.
When getting into very-high-hp arenas (700+ hp?), it's pretty well documented that the 4L80 is more cost-effective to build than the 518. (most of us don't play in that arena, though)

It's like any other major car mod - different folks have different goals.

 

[3175375]

The 4L80 is much bigger and stronger, but I've not read anythign about the 4L60-65-4L70 being junk.
If one used a '4L60', they would want to get the 4L70 version, which has more pinions in the planetaries, more clutch disc and other related improvements, and then see what upgrades make sense.
As for fit, the 518/46RH is a 727 with an OD added on, so it's much larger at the rear, often requiring tunnel mods (at least in the smaller cars).
The 4L60 is sized/shaped more like a typical trans, 4L80 is similar shape but that one is reportedly very bulky.
When getting into very-high-hp arenas (700+ hp?), it's pretty well documented that the 4L80 is more cost-effective to build than the 518. (most of us don't play in that arena, though)

It's like any other major car mod - different folks have different goals.

I had a 95 turbo diesel 3/4 ton suburban and several GM guys that I worked with had told me to ensure that the truck came with the 4L80.

It would seem that with a bigblock Mopar or anything with 300+ horsepower, that one would seek a more heavy duty transmission - you don’t see a 440 coupled with a 904.

Similarly, I have a diesel pusher RV that has the Allison 3000 transmission. I would be terrified if it had anything less…

 

[fury fan]

Not to be argumentative, but just some counterpoints:

I would not expect a 4L60-70 to survive behind the 6.5 diesel - I'd be surprised if GM even offered that.
Diesels make torsionals that will shorten transmission life vs a 'regular' automatic.
Our beloved 727/518 had issues behind Cummins diesels - even when they were lower-powered 12V versions.

There's a big difference between what GM will supply to preserve a warranty/reputation vs what a hotrodder will beef up for personal use, and put significantly fewer miles on.
A 4L65-4L70 rating I saw was 375hp and 380 ft-lbs - and that would be based on 'net' engine ratings. So not out of league with with a stock-ish 383.
And they were used in Escalades, Sierra/Denali pickups with 6.0 liter engines - vehicles that weigh more than most any C-body and with higher towing capacity.

I doubt any of us would install a stock/junkyard 4L60 - we're gonna beef it up. (well, I would install a JY trans for initial installation/evaluation to see how it performed)
And surely we'd look for the version with the highest factory rating and factory improvements (the 4L70E).

FWIW - @furious70 has a beefed A500 behind his turbo'd 383, but IIRC it had lots of upgrades. (that could be considered equivalent to a 4L60 with a *strong* 440?)

I worked for a few years with the Allison 1000-4000 series of transmissions. They are definitely a rock-solid, well-engineered item. Oh, I could tell stories of their toughness...

 

[3175375]

Not to be argumentative, but just some counterpoints:

I would not expect a 4L60-70 to survive behind the 6.5 diesel - I'd be surprised if GM even offered that.
Diesels make torsionals that will shorten transmission life vs a 'regular' automatic.
Our beloved 727/518 had issues behind Cummins diesels - even when they were lower-powered 12V versions.

There's a big difference between what GM will supply to preserve a warranty/reputation vs what a hotrodder will beef up for personal use, and put significantly fewer miles on.
A 4L65-4L70 rating I saw was 375hp and 380 ft-lbs - and that would be based on 'net' engine ratings. So not out of league with with a stock-ish 383.
And they were used in Escalades, Sierra/Denali pickups with 6.0 liter engines - vehicles that weigh more than most any C-body and with higher towing capacity.

I doubt any of us would install a stock/junkyard 4L60 - we're gonna beef it up. (well, I would install a JY trans for initial installation/evaluation to see how it performed)
And surely we'd look for the version with the highest factory rating and factory improvements (the 4L70E).

FWIW - @furious70 has a beefed A500 behind his turbo'd 383, but IIRC it had lots of upgrades. (that could be considered equivalent to a 4L60 with a *strong* 440?)

I worked for a few years with the Allison 1000-4000 series of transmissions. They are definitely a rock-solid, well-engineered item. Oh, I could tell stories of their toughness...

I am not arguing that the 4L60 is not capable of being upgraded. I am just surprised that a company would start an expensive upgrade package with that transmission.

 

[fury fan]

I suspect it is due, at least in part, to the bolt-on converter housing on later versions and smaller size.