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Legendary 4R100 Heavy Duty Transmission

4R100 7.3L Heavy Duty Transmission
Your Cost:
From $3,399.00 to $4,599.00
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REQUIRED INFO: There is a Core Charge on this item. If you send a core in first, your fee will be waived. If you send your core later, you will be charged a refundable $1200 core charge. Choose One:*

Product Description

Valued Customer:

While 2020 was a challenging year for us all, 2021 has its own challenges.  Specifically raw materials to rebuild the Legendary and Hercules Transmissions.

While many of the parts for these transmission parts are produced in house, several of the parts are outsourced.  Over the past 6 months, we have been in contact with our suppliers daily because of the backlog of orders for these outsourced parts.  Most of the shortages are due to the 2020 experience.  The shortages are not just a Dieselsite challenge, but an industry challenge.  All of the manufacturers are jockeying for position to receive raw materials as they become available.  The most frustrating thing that we are experiencing and so are our customers is the lack of information as to when this will get back on track.  

All customers are being kept in the production que, but at this time we are not able to give anyone any firm delivery dates. There will be no penalties for order cancellation.  We apologize for all the delays you are experiencing. 

Thank you for your understanding and support during this difficult time.  We are working diligently to keep in the forefront of getting any material we can to continue production.



Engineered to Last

  • Heavy Duty 4R100 for the 7.3L Powerstroke
  • Designed for demanding  conditions
  • Improved Performance at Affordable Pricing
  • Eliminates sloppy shifting
  • Transmissions usually in stock and ready to ship - short lead times if not in stock
  • Short Lead Times on custom builds
  • Each Unit 100% Dyno Tested – NO DOAs
  • Built in the USA

1999-2003 Ford 4R100 F250 - F550 and Excursion 7.3L Heavy Duty Diesel Transmissions:

Please note: If you have a PTO transmission, you must put a PTO transmission back in.  PTO Cores must be sent ahead for rebuild. 

E4OD, 4R100 Gas, and all Van (E350-E450) Transmissions built upon request. Call for information and pricing.
Several years in the making.
After purchasing Factory Tech Transmissions in April of 2012, we spent the last couple years setting up the lathes and mills to cut special parts, installing blast cabinets, paint booths, and our state of the art $250,000 dynamometer powered by BlueReach Automation. We can duplicate actual driving and load conditions in a truck, including all upshifts and downshifts.


  • Designed for towing performance.
  • Increased power transfer to the rear wheels
  • Improved shift feel
  • More durable than OEM.
  • Clutch material designed to handle extended and elevated temperatures without burning.

Standard Specifications in every transmission:

  • Direct and Forward clutches built with 120% of OEM clutch surface area.
  • Coast Clutch upgraded with 200% of OEM clutch surface area, custom spiral snap ring, and fully cut snap ring groove to hold up to exhaust brakes.
  • Overdrive built with 133% of OEM clutch surface area to hold up to towing in OD.
  • Intermediate clutches built with 133% of OEM clutch surface area.
  • Pump modified for increased line pressure
  • Spiral snap ring over center support.
  • 45 element intermediate sprag

  • Case to center support sealed to prevent internal leakage
  • All steel planetary gears.

  • Every single clutch pack is measured and set to exact clearances- every unit within .003"
  • Torrington bearings throughout.
  • INDUSTRY EXCLUSIVE! High Energy 850°frictions in all gears  - no 4R100 has ever had this. A DieselSite exclusive!
  • Full thickness steels for maximum heat transfer from clutches
  • Every remanufactured part is run through our de-burring machine.

  • New Output Speed Sensor
  • New Transmission Speed Sensor
  • New Transmission Range Sensor
  • New thermal bypass valve
  • Custom In-house built valve body for shorter shift duration - firmer shifts and longer clutch life.
  • We have a transmission hydraulic circuit pressure test machine to insure no internal leakage occurs.

  • Every Unit fully tested in our own Transmission Dynamometer - No DOA units leave here!

  • There are many more modifications we do to improve performance and reliability

  Shipping cost is based on your location. If you need liftgate service, you will need to specify this and be aware that there is a 100.00 additional charge for this service - each time the lift gate is needed. If you need a lift gate for delivery and pick-up, the additional shipping cost will be 200.00. We will handle all the shipping arrangements getting the transmission to you in a shipping container and arrange the pick-up of your core when you are ready. So, this shipping cost is all inclusive (other than liftgate if needed) to cover shipping to you and the shipping to get the core back to us.

Core Charge. The transmission is shipped to you in a molded shipping container. We must get this case back with your transmission core. If you send back your core without the case, you will only get $1000.00 of your core fee returned. The case has a $200.00 core fee on it. If you ordered a TC and do not send your tc core back with your transmission, there will be another $150.00 deducted.

Custom Tuning Notes: Ask your tuner to leave the line pressures set at stock levels. Increasing line pressures electronically will only cause very harsh shifts.

Options for custom builds include:

  • MagHytec Deep Transmission Pan
  • 300M Advanced Alloy Billet Input Shaft
  • 300M Advanced Alloy Billet Intermediate Shaft
  • 300M Advanced Alloy Billet Output Shaft
  • Single Sided Intermediate Clutch Pack- Designed for high rpms/ high hp drag racing applications. This is a must for Ford Lightning owners!

E4OD, 4R100 Gas, and all Van (E350-E450) Transmissions built upon request. Call for information and pricing.