alpine44
Member
- 397
- 17
- 18
- Location
- Asheville, NC - Elkton, MD
Last weekend I put a 700R4 with NP241C in my M1009 with 4.10 gears in a 14 bolt FF axle and 315/75R16 BFGoodrich T/A KO2 (34.5" diameter) tires. This is the truck in my avatar.
I built this tranny about 2 years ago during a long, cold Montana winter but did not have the time or energy to make the switch sooner. Now I wish I had bolted this drivetrain in the truck the day after finishing it. The M1009 drives so much nicer with the 700R4.
After a couple short test runs in the last few days, I went on a 150 mile roundtrip today with about 40% interstate, 40% rolling hill highways, and 20% steep and tight mountain roads.
The M1009 with the bigger tires and 4.10 axle ratio did always well in the mountains with the TH400 but everything faster was painful. Now it actually feels like a truck on the highway/interstate and not like a chainsaw with wheels. The combination of transmission gearing, axle ratio, and tire size is perfect.
The truck is both lively while accelerating from a stop or out of a hairpin turn and much, much quieter at the top end. I did not go much faster than 70 mph today due to traffic. Cruising on a highway feels now very similar to burbling down a forest service road. The engine is slightly below max torque and moves the truck effortlessly. Reminds me of a downeast lobster boat at economy cruise.
I wired the TCC up for engagement via a push-button and disengagement via the brake light. This setup makes the 700R4 feel like a 5 speed transmission. With the TCC locked the automatic downshift into 3 (still locked) takes care of regular grades. If it gets steeper a quick tap on the brake will get the torque converter going, which will take care of even the steepest grades here in Western North Carolina. In really tight turns it downshifts into 2 and accelerates out of the turn smoothly and swiftly (for its power to weight ratio). Downshift into 2 with the TCC locked needs to be avoided as it is very harsh without the converter fluid acting as a cushion. The double downshift acceleration from 4 is impressive in the unlocked mode though.
I am certain that a similar result can be achieved with a 4L80 and some controller programming.
I opted for the 700R4 since I got the core and the T case for next to nothing and because this combo does neither require any exotic/expensive parts nor any modifications to the driveshafts. We will see how long it lasts.
I still have the original drive train as a backup and the neighbor who helped me with the installation on his lift offered me another 700R4/NP241 for less than scrap value. He is a professional auto mechanic and was somewhat impressed when I drove off his property, pushed by the first automatic transmission I ever rebuilt in my life.
When I first looked at the disassembled valve body I was doubting my sanity of choosing a DIY rebuild but the guts of the 700R4 turned out to be fairly straight forward. Many thanks go out to Earl at Bozeman Transmission for his advice on what to change and how to set up the friction packs, him lending me the needed tools over weekends, and for double checking some of the critical tolerances.
PS: Before going on the longer trip I changed the fluid lines to the radiator so that the fluid returns to the transmission from the (cooler) bottom of the heat exchanger. This seems saner in the current 80 F weather than the original routing where hot (185 F) oil returns from the top of the radiator to the transmission. Next step is a temperature gauge and then possibly an auxiliary cooler with thermostat valve at the transmission if needed. I did the test drive today with a transmission pressure gauge hooked up to catch any anomalies early.
I built this tranny about 2 years ago during a long, cold Montana winter but did not have the time or energy to make the switch sooner. Now I wish I had bolted this drivetrain in the truck the day after finishing it. The M1009 drives so much nicer with the 700R4.
After a couple short test runs in the last few days, I went on a 150 mile roundtrip today with about 40% interstate, 40% rolling hill highways, and 20% steep and tight mountain roads.
The M1009 with the bigger tires and 4.10 axle ratio did always well in the mountains with the TH400 but everything faster was painful. Now it actually feels like a truck on the highway/interstate and not like a chainsaw with wheels. The combination of transmission gearing, axle ratio, and tire size is perfect.
The truck is both lively while accelerating from a stop or out of a hairpin turn and much, much quieter at the top end. I did not go much faster than 70 mph today due to traffic. Cruising on a highway feels now very similar to burbling down a forest service road. The engine is slightly below max torque and moves the truck effortlessly. Reminds me of a downeast lobster boat at economy cruise.
I wired the TCC up for engagement via a push-button and disengagement via the brake light. This setup makes the 700R4 feel like a 5 speed transmission. With the TCC locked the automatic downshift into 3 (still locked) takes care of regular grades. If it gets steeper a quick tap on the brake will get the torque converter going, which will take care of even the steepest grades here in Western North Carolina. In really tight turns it downshifts into 2 and accelerates out of the turn smoothly and swiftly (for its power to weight ratio). Downshift into 2 with the TCC locked needs to be avoided as it is very harsh without the converter fluid acting as a cushion. The double downshift acceleration from 4 is impressive in the unlocked mode though.
I am certain that a similar result can be achieved with a 4L80 and some controller programming.
I opted for the 700R4 since I got the core and the T case for next to nothing and because this combo does neither require any exotic/expensive parts nor any modifications to the driveshafts. We will see how long it lasts.
I still have the original drive train as a backup and the neighbor who helped me with the installation on his lift offered me another 700R4/NP241 for less than scrap value. He is a professional auto mechanic and was somewhat impressed when I drove off his property, pushed by the first automatic transmission I ever rebuilt in my life.
When I first looked at the disassembled valve body I was doubting my sanity of choosing a DIY rebuild but the guts of the 700R4 turned out to be fairly straight forward. Many thanks go out to Earl at Bozeman Transmission for his advice on what to change and how to set up the friction packs, him lending me the needed tools over weekends, and for double checking some of the critical tolerances.
PS: Before going on the longer trip I changed the fluid lines to the radiator so that the fluid returns to the transmission from the (cooler) bottom of the heat exchanger. This seems saner in the current 80 F weather than the original routing where hot (185 F) oil returns from the top of the radiator to the transmission. Next step is a temperature gauge and then possibly an auxiliary cooler with thermostat valve at the transmission if needed. I did the test drive today with a transmission pressure gauge hooked up to catch any anomalies early.
Last edited: