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One Tough Tranny: A Mid-Level Ford Transmission Rebuild

The Ford 4R100 automatic transmission was introduced in 1999 and was mated to the 7.3L Power Stroke diesel engine. The 4R100 is a computer controlled 4-speed automatic with a 1,000 lb-ft capacity from the factory. The last year of production was 2003. This means that most of the Ford F-250 and F-350 trucks that run this automatic transmission have seen a lot of miles. While some grumble about their durability, the truth is, the 4R100 has performed well, and thousands are still on the road today.

Once your automatic transmission is at the shop, it will be disassembled, cleaned, and the parts will be inspected. Often, trouble with the transmission can point to other issues. Age is not the only reason for transmission failure: One example is overheating due to a bad transmission cooler. Close inspection is required to ensure that all transmission parts are either replaced or repaired as needed and that all required repairs are made to the system as a whole.
Once your automatic transmission is at the shop, it will be disassembled, cleaned, and the parts will be inspected. Often, trouble with the transmission can point to other issues. Age is not the only reason for transmission failure: One example is overheating due to a bad transmission cooler. Close inspection is required to ensure that all transmission parts are either replaced or repaired as needed and that all required repairs are made to the system as a whole.

However, like any high-mile automatic transmission, your 4R100 is sure to have some wear that should be addressed before you pump more power through it. Though it’s a good transmission, the 4R100 can be made be better.

To learn about the upgrades available for the 4R100, we contacted Remac Transmission: They explained that there are generally three options, a stage-1, stage-2 or stage-3 rebuild. While stage-1 is a little better than stock, it is only recommended for light-duty use. The truck we’ll be installing this upgraded 4R100 into, however, is a workhorse. It used to haul parts and tools for a local diesel shop and as a daily driver would tow trailers of all sizes. For this type of usage, Remac recommended a stage-2 rebuild for better durability and drivability. The stage-2 is best for normal to heavy-duty use. The stage-3 rebuild, Remac explained, is really for extreme duty, race applications, and might be too harsh for daily use. In addition, a stage-3 rebuild is more likely to overheat when idling for extended periods than the milder, stage-2 build. (This type of long term idling is usually found on work trucks that are virtually never turned off.)

Follow along, and we’ll show you the highlights of what it takes to make a superior 4R100 transmission that will meet your needs and perform great for work and play. DW

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We install our new 4R100 and take it for a test drive.

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1. Here you see the actual heart of the Ford 4R100 transmission. This is the actual transmission; the aluminum case simply holds the parts that make up this assembly and allow it to mate to the engine and driveline and contain the valve body mounting flange and fluid passages.
1. Here you see the actual heart of the Ford 4R100 transmission. This is the actual transmission; the aluminum case simply holds the parts that make up this assembly and allow it to mate to the engine and driveline and contain the valve body mounting flange and fluid passages.

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2A/2B. The transmission pump is a Gerotor style unit. These positive displacement pumps work best with tight clearances; in image B, you can see that this pump housing is warped. Remac always checks these pumps and machines them to a .002 tolerance for maximum efficiency and long life.
2A/2B. The transmission pump is a Gerotor style unit. These positive displacement pumps work best with tight clearances; in image B, you can see that this pump housing is warped. Remac always checks these pumps and machines them to a .002 tolerance for maximum efficiency and long life.
3. The inspection process revealed that the clutch fiction plates were worn and showed signs of heat damage. These wear parts will be replaced with new and better components, as is standard, regardless of condition.
3. The inspection process revealed that the clutch fiction plates were worn and showed signs of heat damage. These wear parts will be replaced with new and better components, as is standard, regardless of condition.
4. Here you can see three different overdrive ring-gears for the 4R100 transmission. All of them show signs of wear, and only one is even worth considering for reuse.
4. Here you can see three different overdrive ring-gears for the 4R100 transmission. All of them show signs of wear, and only one is even worth considering for reuse.
5. The overdrive ring-gear for our 4R100 transmission only had 15 percent of the teeth left on it. It’s surprising that it didn’t fail with this much wear. Of course, it will be replaced with a new unit.
5. The overdrive ring-gear for our 4R100 transmission only had 15 percent of the teeth left on it. It’s surprising that it didn’t fail with this much wear. Of course, it will be replaced with a new unit.
6. This is the forward clutch drum, and it is used in all 4 forward gears. There are two styles; one has less spline engagement (top). Remac checks the spline for wear and replaces the clutch drum as needed. They also upgrade the unit to the full spline style (bottom) if yours is a half-spline style for more durability and longevity.
6. This is the forward clutch drum, and it is used in all 4 forward gears. There are two styles; one has less spline engagement (top). Remac checks the spline for wear and replaces the clutch drum as needed. They also upgrade the unit to the full spline style (bottom) if yours is a half-spline style for more durability and longevity.
7. With everything cleaned and checked, it’s time to begin the rebuild of our 4R100.
7. With everything cleaned and checked, it’s time to begin the rebuild of our 4R100.
8. Remac offers three levels of rebuild, stage-1, stage-2 and stage-3. The stage-1 is a basic stock rebuild and uses a 5-clutch pack (right). Stage-2 and stage-3 rebuilds get an 8-clutch pack (left). Regardless of build level, Remac uses only new parts in the clutch pack with improved clutch materials and better steel friction plates.
8. Remac offers three levels of rebuild, stage-1, stage-2 and stage-3. The stage-1 is a basic stock rebuild and uses a 5-clutch pack (right). Stage-2 and stage-3 rebuilds get an 8-clutch pack (left). Regardless of build level, Remac uses only new parts in the clutch pack with improved clutch materials and better steel friction plates.
9. Leo Glasenbrenner, owner of Remac Transmission, and technician Brian Ariano are seen here beginning the rebuild of our 4R100. It takes two to get the output shaft and some components into the case. Other than this, a single technician can do the rebuild. Once the output shaft is installed, the tail housing is put on, followed by the focus shifts to the front of the transmission.
9. Leo Glasenbrenner, owner of Remac Transmission, and technician Brian Ariano are seen here beginning the rebuild of our 4R100. It takes two to get the output shaft and some components into the case. Other than this, a single technician can do the rebuild. Once the output shaft is installed, the tail housing is put on, followed by the focus shifts to the front of the transmission.
10. At Remac, welding the low drum in the 4R100 for reinforcement is standard for all diesel applications, as well as for gasser race rigs running the 4R100. Every third spline is tig welded for superior strength.
10. At Remac, welding the low drum in the 4R100 for reinforcement is standard for all diesel applications, as well as for gasser race rigs running the 4R100. Every third spline is tig welded for superior strength.
11. When the pump is installed, the transmission assembly is essentially complete. The only thing left to put on is the valve body and other components that ride on the bottom of the case are under the pan.
11. When the pump is installed, the transmission assembly is essentially complete. The only thing left to put on is the valve body and other components that ride on the bottom of the case are under the pan.
12. Glasenbrenner explains that Remac does make modifications to the valve body, but only on state-2 and stage-3 rebuilds. Seen here, a modification is being made on the line pressure modulator circuit.
12. Glasenbrenner explains that Remac does make modifications to the valve body, but only on state-2 and stage-3 rebuilds. Seen here, a modification is being made on the line pressure modulator circuit.
13. An improved line valve was installed. This upgrade provides firmer shifts compared to the stock line valve. The result is firmer upshifts between 1-2 and 2-3. Firmer shifts mean less heat and longer trans life. When racing, it can also mean lower ETs.
13. An improved line valve was installed. This upgrade provides firmer shifts compared to the stock line valve. The result is firmer upshifts between 1-2 and 2-3. Firmer shifts mean less heat and longer trans life. When racing, it can also mean lower ETs.
14. Stage-2 and stage-3 rebuilds also get a modification done to the shift plate. This upgrade will result in better shift characteristics over stock. This means better shifts when towing a load and more responsiveness from the transmission when you need it most.
14. Stage-2 and stage-3 rebuilds also get a modification done to the shift plate. This upgrade will result in better shift characteristics over stock. This means better shifts when towing a load and more responsiveness from the transmission when you need it most.
15. Remac uses only Ford OEM solenoid packs on their Ford Trans rebuilds. They have proven reliable over the long haul.
15. Remac uses only Ford OEM solenoid packs on their Ford Trans rebuilds. They have proven reliable over the long haul.
16. Once the valve body is installed, the transmission is ready to have the pan bolted on, and then it’s ready to ship. Remac ships with the stock sheet metal pan, unless otherwise requested.
16. Once the valve body is installed, the transmission is ready to have the pan bolted on, and then it’s ready to ship. Remac ships with the stock sheet metal pan, unless otherwise requested.
17. Here is our better than new Ford 4R100 transmission. Remac ships its transmission with a torque converter. The torque converter is prefilled with EOM spec transmission fluid.
17. Here is our better than new Ford 4R100 transmission. Remac ships its transmission with a torque converter. The torque converter is prefilled with EOM spec transmission fluid.
Source:

Remac Transmissions . 909-592-1006 . Remactrans.com

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