| Author | Message | ||
| Jack Conrad (Jackconrad)
Rating: N/A |
I am collecting the components to install a Jake Brake on our 8V71/740 auto. transmission. I downloaded all the available information from the Jacobs Engine Brake website. The Operarors Manual addresses automatic transmissions as follows: "A pressure sensing switch will de-activate the Jacobs Engine Brake when the engine speed falls below approximately 1000 RPM, or when the transmission shifts from lock-up to converter operation (usually abour 10-25 MPH, depending on the transmission type)." Looking in my Allison HT 700 series manual, I found a lock-up test port. The manual states that lock-up occurs when the rear govenor pressure is within 10 PSI of the main pressure. Main pressure is 90 PSI at idle and increases to 140-175 in all forward ranges. My questions are: Can I install a Normal Open pressure switch in the lock-up test port to de-activate the Jake Brake (and prevent stalling the engine) when slowing? What pressure should this switch "trip" at? (From Hydraulic schmatic it appears that there is pressure available at test port only when converter is in lock-up mode) I plan to install a throttle position sensing switch on the air throttle actuator to allow Jake to operate only when throttle is at idle position. This will allow continued use of the existing fast idle. Thanks in advance, Jack | ||
| jimmci9 #2 Rating: N/A |
from the jake installations ive seen, most use the buffer-screw style no/nc switch...if the engine is at idle, pressure will be down in the transmission...and the jakes should/will only work with the throttle closed... | ||
| Brian (Bigbusguy)
Rating: N/A |
I would try the test port , If you had factory A/C and not using it you may already have some pressure switchs you can take off that may work . On my 4905 it had some type of low psi air switch hooked to the air throttle to turn them off at idle. Now if I can just find a set of jakes to put back on  Brian 4905 Klamath Falls Oregon | ||
| Geobus (4108gmc)
Rating: N/A |
For what its worth, I just had a set installed on my 8v71 but with a v730. I think it is easier to install them on a V740. I really don't know the details but you might want to talk to Jim in service at Inland Diesel, Milwaukee, WI (262-781-7100). He will remember my coach since they don't get too many and it was only 2 months ago. They did't use the buffer switch setup, but added a micro switch to the air throttle. It sounds like what you are trying to do. They can help and did a great job. To save a little money I did the work of threading the wire needed to operate the Jakes. I think I pulled 6 conductors and they used 3. Have a great day. |