Speed Gems Transmission Adapters

Speed Gems Transmission Adapters Speed Gems Transmission Adapters We are currently building adapters for many of the great but overlooked nostalgic motors of the ‘50’s and ‘60’s. YUCK.

Over the years, many rodders have switched their cars over to small block Chevy motors simply because there weren’t any decent transmissions available for the motor that was already in the car. Who could blame them? After all, why would you keep a 394 Olds if all you could run behind it was a Slim Jim? Or, a 401 Buick Nailhead with a Dynaflow? How about a ’53 331 Hemi with a Fluid Drive? Bendtsen’

s Transmission Adapters started as businesses often do, to fill a void or a need in a market place. We evolved from a full service transmission shop that grew to specialize in antique and obsolete transmissions. I started building engine to transmission adapters for two reasons. One is that it is getting extremely expensive to rebuild the old transmissions. Not only are some of the parts getting scarce (try buying a new sprag or roller clutch for a Dynaflow or Turboglide torque converter), but the knowledge level of the people available to rebuild these units competently is falling by the wayside. Transmissions had more internal changes back in the 50’s than they do today. Four speed Hydramatics to most people appear to be the same from the outside, but many of the internal parts (mostly hydraulic control) were not interchangeable from year to year, or from model to model. These transmissions had extremely touchy throttle pressure linkages that required them to be adjusted correctly or a failure would occur. Carburetor swaps usually made adjustments very difficult if not impossible. These adjustments are very similar to the detent cables used in 700R4 and other modern transmissions. They control all internal pressures inside the transmission. Throttle pressure must raise quickly when engine load increases. Out of adjustment one way (low pressure) and you will have burned clutches and bands. Out the other way (high pressure) and you can break shafts and splines. Vacuum modulators changed the way transmissions received their information about engine load. Linkage & cables became just “kickdown” devices. This is why people still don’t understand the difference or relationship as to why the 700R4 and similar transmissions require such precise adjustments, they are simply going back to the way things were 50 years ago! Electronics made external adjustments obsolete. There are no longer any mechanical adjustments. All pressure and shift timing is now taken care of by computer. Changes internally to today’s transmissions are usually well documented not only by the manufacturer, but also by technical subscription to a number of aftermarket companies. Not so in the past. When the old mechanics die, a lot of knowledge goes with them. I listen closely when I find an old transmission mechanic that still remembers fixes for old transmissions. The second reason that I’m designing and building adapters is that I would like to see more people run alternative engines in their cars rather than small block Chev motors. The V8 engines that many of us fondly remember from our youth are making a long overdue comeback in the way of the Resto-Rod. Personally, I loved 348’s and 409’s, but the Ford Flathead, the Buick Nail head, the Olds rocket, the Hemi’s, the straight 8’s, & many more popular multi-carb motors are all still very popular. Just check the number of websites on each of these different makes and you will find a huge following. Rodding started as a very creative hobby/sport. Working with what one could afford at the time, we all built our cars with a lot of imagination. This trend, of late, to plop a small block Chev motor into every rod built has made me feel that the hobby/sport has totally changed. Car shows are getting boring due to the rubber stamp/production line type of car building going on around the country today. Is anyone besides me tired of looking at what seems to be the same car over and over and over again? Every car in the world it seems has a Chev small block in it. I’m partial to seeing drive trains that are unusual. I like to see what the next guy has done to his car that no one else has ever done before. It doesn’t matter if it looks like it’s been cobbed together or if it even works, at least somebody tried something different. We here at Bendtsen’s Transmission Adapters plan to adapt the old motors of the ‘50’s and ‘60’s to modern transmissions, so you can use a motor with some personality/Attitude? I plan to lead a one-man revolution against the BORING and UNCREATIVE trend of planting small block Chevy motors into everything that moves. Enclosed you will find a small list of alternative nostalgic motors, along with a few new motors, that we now provide adapters for. Most of our adapters aren’t made by anyone else, anywhere. None of my adapters require any block or transmission case modifications! They are easy to bolt on at home. They are high quality, and expensive. Well worth the money.

A bellhousing does more than connect your engine and transmission.It helps bring the entire drivetrain together.That’s w...
09/04/2026

A bellhousing does more than connect your engine and transmission.
It helps bring the entire drivetrain together.

That’s why proper fitment and precision engineering matter. Speed Gems bellhousings are built for performance, reliability, and the demands of your build. Right here in the USA.

Build it right from the start.

We’re hitting the road!Here’s where you can catch the Rod Doors, Speed Gems, and Porter Mufflers crews at some upcoming ...
09/02/2026

We’re hitting the road!

Here’s where you can catch the Rod Doors, Speed Gems, and Porter Mufflers crews at some upcoming events!

Save the dates, bring your build, and come say hi! We’d love to see you there!

The right starter is about more than getting your engine to turn over—it needs to work properly with the rest of your se...
08/28/2026

The right starter is about more than getting your engine to turn over—it needs to work properly with the rest of your setup.

Mismatched components can lead to inconsistent starts, fitment issues, and premature wear. That’s why our starter solutions are selected and engineered for proper fitment and dependable performance.

Because reliability starts with the right combination. ⚙️

Shop at https://zurl.co/SpeedGems

Thinking about pairing a Ferrari/Maserati F136 engine with a Nissan CD009 transmission?Throttle Grotto walks through the...
08/24/2026

Thinking about pairing a Ferrari/Maserati F136 engine with a Nissan CD009 transmission?

Throttle Grotto walks through the complete installation of our Speed Gems adapter kit, including everything you’ll need to bring the two together.

Watch the full installation guide: https://zurl.co/ThrottleGrotto

Ready to start your own swap? Use code **THROTTLEGROTTO** for 10% off the kit!

We’re officially one month away from the Hot Rod Hangout! 🏁Join Speed Gems, Wilcap, Rod Doors, and Porter Mufflers for a...
08/19/2026

We’re officially one month away from the Hot Rod Hangout! 🏁

Join Speed Gems, Wilcap, Rod Doors, and Porter Mufflers for an afternoon of cars, food, beverages, and good company. Bring your ride, look around, and hang out with fellow enthusiasts!

📅 Friday, September 18
⏰ 11 AM–2 PM
📍 806 S. Division St., Waunakee, WI

Save the date and come hang out with us!

We’re headed to Cheaterama! 🏁Porter Mufflers will be there as a featured vendor, and we’re bringing our sister company, ...
08/18/2026

We’re headed to Cheaterama! 🏁

Porter Mufflers will be there as a featured vendor, and we’re bringing our sister company, Speed Gems, along for the ride. Come find our booth, check out what we’ve brought, and hang out with us!

📍 Cheaterama — 1111 Milwaukee ave. South Milwaukee Wisconsin
📅 Saturday, August 22

Come say hi! We’ll see you there! 👋

NEW RELEASE - NOW LIVE! The redesigned Speed Gems FO2501 connects a Ford 429/460 big block to a modern Ford automatic tr...
08/17/2026

NEW RELEASE - NOW LIVE!

The redesigned Speed Gems FO2501 connects a Ford 429/460 big block to a modern Ford automatic transmission, including the 6R80 and 4R70W.

✅ No grinding required
✅ Bolt-on installation
✅ Powermaster high-torque starter included
✅ CNC-machined in Waunakee, Wisconsin

Big block power meets modern overdrive.

Ordering is now live! Non-preorder kits will begin shipping 8/31/26.

https://zurl.co/transmissionadapters

Quality you can see. Performance you can trust.From precision machining to American craftsmanship, Speed Gems transmissi...
07/09/2026

Quality you can see. Performance you can trust.

From precision machining to American craftsmanship, Speed Gems transmission adapters are built to keep your project moving for years to come.

Missed us at Back to the 50’s? You can still save! ⚙️Our Back to the 50’s Sale is available for a few more days.🎉 Use co...
06/21/2026

Missed us at Back to the 50’s? You can still save! ⚙️

Our Back to the 50’s Sale is available for a few more days.

🎉 Use code BT50S for 10% OFF at .gems , .official , and .

⏰ Sale ends 6/24.

Cannot be combined with other sales or discounts.

Day 1 We’re set up and ready to go at the Back to the Fifties car show!Stop by Speed Gems at Booth 16-3 to talk transmis...
06/19/2026

Day 1

We’re set up and ready to go at the Back to the Fifties car show!

Stop by Speed Gems at Booth 16-3 to talk transmission adapter kits and your next engine swap project. We’d love to see you!

📍 Booth 16-3

Address

806H S Division Street
Waunakee, WI
53597

Opening Hours

Monday 8am - 4:30pm
Tuesday 8am - 4:30pm
Wednesday 8am - 4:30pm
Thursday 8am - 4:30pm
Friday 8am - 4:30pm

Telephone

(763) 767-4480

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