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HomeShop by DepartmentPerformanceTransmissionsTransmissionSuncoast 46RH Cat 1 450 HP Transmission 1989-1993 4WD (WITHOUT CONVERTER)

Suncoast 46RH Cat 1 450 HP Transmission 1989-1993 4WD (WITHOUT CONVERTER)

Thoroughbred Sku #: SUNSC-46RHCAT1-8993-4WD-LC-CRE

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Many stock replacement parts such as turbos, injectors, injection pumps, and high pressure oil pumps have a core charge that is associated with the new replacement part. You must return the old part to receive a refund on the core charge.

In some cases, the core is not reusable, such as in the event of a cracked case, at which point the core deposit would not be credited as the core component is not reusable.
Cores that have been disassembled and/or have missing and/or damaged major components will not receive full core credit.
Returned cores must be on a "like-for-like" basis, meaning that the returned core has the exact same fitment as the remanufactured component that was purchased. If the core is not "like-for-like," your core may not be eligible for return/credit.
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If you plan on returning your core you have two options.

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OPTION 1: You can accept the core charge, which means you will be charged for the part AND the core at time of purchase. You still have the option to send it back, and if you do, the core will be refunded back on the card used, presuming the core meets core criteria and the core is returned within 30 days from the time your order is received. If you return your core after 30 days you may refer to the Core Charge Timeline below as to how you will be refunded.

Core Charge Timeline

If the core is returned after 30 days, 90% of the core will be refunded.
If the core is returned after 60 days, 70% of the core will be refunded.
If the core is returned after 90 days, 50% of the core will be refunded.
After 6 months cores will be accepted at Thoroughbred’s discretion.

OPTION 2: You can defer the core charge. If you defer, you will not be charged for the core at the time of purchase. You will have 21 days from the time your order is received to send the core back. If the core is not received within the 21 days, your credit card will be charged for the core amount on your order. If you return your core after 21 days, you may refer to the Core Charge Timeline below as to how you will be refunded. When Core deferral (Pay Core Charge Later) is limited to payment by credit card only. ***When using PayPal or Affirm as your method of payment “Core Deferral (Pay Core Charge Later)” is not available. The core must be paid at time of purchase. ***

Core Charge Timeline

If the core is returned after 21 days, 90% of the core will be refunded.
If the core is returned after 60 days, 70% of the core will be refunded.
If the core is returned after 90 days, 50% of the core will be refunded.
After 6 months cores will be accepted at Thoroughbred’s discretion.

Core Return Procedure

Please keep all original packaging of your new item to be used for the core return.
Drain all fluids: oil, fuel, etc. out of the core before it is returned.
Place any plastic plugs or caps received on the new item back onto the core.
To insure UPS, Fed Ex, or USPS will not reject the package due to fuel or oil leakage, please wrap the core in a plastic garbage bag.
Place core inside the box.
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Please provide a tracking number to [email protected]. Without a confirmed tracking number we cannot guarantee your core refund
If you have questions please call our core department 859-737-4966 ext. 5

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Product Details

Product Name: Suncoast 46RH CAT 1 450 HP TRANSMISSION 1989-1993 4WD (WITHOUT CONVERTER)
Manufacturer: Suncoast
Manufacturer Part #: SC-46RHCAT1-8993-4WD-LC
Thoroughbred Diesel Part #: SUNSC-46RHCAT1-8993-4WD-LC
Fitment Notes: 1989-1993 Dodge Diesel

For over two decades SunCoast has continually led the the industry in both innovation and performance. Dating back to the days of Redneck nationals and Team Green before outlaw racing was even thought of SunCoast transmissions were breaking records and winning world championships. The phrase "copied but never caught" could never be truer than now.

Each one of our Dodge Torqueflite transmissions receive what we call our base packages. This base package can be built and improved upon with a plethora of options and upgrades to suit your individual needs. These units are not "cookie cutter" units but rather something individually catered to your specific needs. Each one of our calibrations to the valve body, pump, seperator plate, and even the clutch stack-ups are meant with your intended usage in mind. These units include have many upgrades from the factory not just for performance but restoring hydraulic integrity to some very crucial circuts, Here are some listen below:

The Billet Band Package

The Torqueflight transmission utilizes a band to shift the transmission into 2nd gear, then this band is release when shifting into 3rd gear. This band is wraps around the direct drum (right behind the transmission pump)this drum house the direct clutches (3rd gear). When thinking about the amount of torque these trucks can make coupled with the torque multiplication of the converter and it soon becomes apparent why this area could be problematic. The band itself from the factory is a very flexible band, these band will stretch and require constant adjustment. When even modest attempts of increased apply pressure occur these band break due to the flimsy construction. You will some aftermarket attempt to use a very rigid material to keep these from flexing or breaking. SunCoast took a different approach and just redesigned the band all together. Each one of our units recieves a new SunCoast custom billet band machined in house. This new SunCoast billet band is also lined with a Carbon Fiber friction material offering the best friction coefficent available.

Our next focus is with the hydraulic integrity of this band acuation. The best band in the world is useless without proper clamping force when apply and a quick release off the drum when needed. This is where our SunCoast billet 2nd gear servo comes into play. The factory uses a cast servo, the servo offers two simple o'rings to help control cross-leaking within the bore. This bore over time will wear, as it wears cross leaking occurs causing lazy shifts, slips going into 2nd gear, and of course in some events bind-ups and dragging of the band going into 3rd. SunCoast corrects this by installing a custom cnc'd billet intermediate servo. This servo is made with 4 sealing rings both teflon and rubber, That is double what the factory uses. This servo is also larger in apply area, over 20% larger than the factory. This larger apply surface area allows for not only a dramatic increase in apply pressure giving you an enormous amount of clamping load, but this also allows for a faster shift time. As almost everyone in our industry lust over the additional clamping force and much quicker apply time, we often overlook the release of the band. The release of the band can be just as import if not more. When they drag on release it can cause bind-up issues, scoring of the band material, and of course premature wear. SunCoast also modifies the length of this servo to achieve much crisper shifting.

Now that we have increased the clamping force we must address the two other problematic issues with the band strut and the band anchor. Just as an engine builder would change to a stronger chrome moly push rod when changing the camshaft to ensure no deflection occurs the same can be said for the band strut and band anchor. With now having a more apply pressure on the band we must correct or issue with the factory band strut as well. SunCoast replace the factory band strut with a much stronger billet band strut to keep any deflection at bay. The band anchor is also replaced with a billet one as well.

Throwing out the garbage

The factory, through all of the engineering they have done somehow thought it would be a good idea to put a plastic accumalator piston in this unit. We are still left scratching our head everytime we see a broken one. These very inexpensive plastic pistons will in fact break over time. This is not a matter of if but when this will happen. When you couple this with the fact that this piston also has issues with cross leaking within the bore, It only make sense that it belongs in the trash. Here at SunCoast we manufacture our own new piston that has additional sealing rings to fix this issue. This accumalator piston is also designed with annular grooves to keep side loading from transpiring.

Deflecting the blame

Deflection can occur in many ways, in engineering deflection is the degree to which a structural element is displaced under a load. When we start talking about loads under hydraulic apply priciples and deflection is always around us.

In both the direct and forward drum we see deflection and side loading contribute to repeated failures daily. At SunCoast we have addressed the issue with the direct drum by making several improvements. The factory cast piston has several key issues we felt we needed to address. On every one of our Competition transmissions we simply replace the factory direct drum with a full billet one. While this is very costly we felt it neccassary despite the cost. This upgrade is not needed for mildly modded vehicles and we can resolve the key issues by simply replacing the factory piston. Here they key issues with this piston and how we address it:

Crossleaking - The factory piston over time will wear in the inner diameter allowing it to wear and even cause side-loading. this uneven wear and side-loading can further aid the deflection occurring with the higher line pressure from say a shift kit. This is alleviated by simply changing the material that is much more resistant to wear.
Deflecting - in attempts to achieve greater clamping force most builders will modify the seperator plate and valve body to achieve both more volume and line pressure. The only issue is the factory "cast" piston was not designed for this. The modest attempts by the builder is now causing deflection and uneven apply. We correct this issue using a custom SunCoast cnc'd direct piston that will not deflect under the most extreme loads.
Clamping - when SunCoast sat down to design our new billet direct piston we knew we wanted to address the apply surface area, so we did just that. The new SunCoast billet direct piston has a larger than factory apply area. This along with the fact it is billet allows us to achieve the greatest undeflected apply pressures in the industry.
Stack-up - SunCoast has specifically designed these apply pistons in both the forward and direct drums to a custom design allowing our own propriertary custom clutch and steel stack-ups. We manufacture each billet piston for both the direct and forward piston with exact tolerences in mind.
Release - The SunCoast custom redesigned billet direct piston also comes with our own custom spring count with a set of custom return springs. This was an important issue we wanted to address in the direct clutch, after all the release is just as valuable as the apply.

Each one of our builds receives new custom billet direct and forward apply pistons. We are proud say that both the forward and direct pistons are designed, engineered, tested, and manufactured here in the U.S.A. by American workers.

The Valve Body

In many way the valve body is the brain of the transmission. This one simple piece can simply be the life or death of a transmission. Each one of our SunCoast custom built transmission's receive one of our custom calibrated valve bodies. SunCoast has specifically calibrates each valve body for that customers specific needs. We also offer a variety of additional upgrades to these as well. We offer full manual setup's in both forward and reverse shift patterns. These can also be built with custom transbrake's as well.

Suncoast Transmission Features:

SunCoast custom billet second gear band lined with Carbon Fiber
SunCoast billet band strut
SunCoast billet band anchor
SunCoast custom billet direct piston
SunCoast custom billet forward piston
SunCoast billet 4 ring accumulator piston
SunCoast Billet upgraded governor solenoid
SuncCoast custom Billet intermediate band servo
Multiple input shaft options (some require custom torque converter)
6 Raybestos custom frictions and 6 Kolene steels in direct clutch
4 Raybestos custom frictions and 3 Kolene steels in forward clutch
10 Raybestos custom frictions and 9 Kolene steels in Overdrive Direct clutch
6 Raybestos custom frictons and 6 Kolene steels with custom apply plate
SunCoast custom calibrated valve body
New bushings
New torrington thrust bearings
New thrust washers
All new upgraded electronics
SunCoast custom calibrated pump
For more information on Suncoast call us at 1-859-737-4966.

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