I'm getting mixed facts about my Jakes

[Nick Badame Refrig/ACC]

Spoke with Keith Crawford today, he is telling me that I don't need to do anything with my HT740 trans..

He said that the 740 locks up the tourq converter when you let go of the throttle..??..?? Is this true?

If not, that would explain why, I'm not feeling the Jakes as well as I should. I'm leaning towards what Brian Deihl has

enlightened me on with the external electric over hydraulic solenoid..

Anymore facts on this??

Thanks in advance
Nick-

[Brian Diehl]

Nick, The reports I have heard from various people indicate the HT series of transmissions all behave similarly, but each a little bit differently depending upon how the valve bodies were calibrated and the model of valve body.  The best bet for you is to actually go experiment with your tranny on a steep hill and find out when it goes into lockup.  It is very easy to tell when you are in lockup because when you press on the accelerator you get no increase in rpms if the road speed does not go up.  Same on taking your foot of the accelerator.  If your rpms drop without the road speed dropping then you're not in lockup.  Many people have a hard time telling when lockup occurs because it happens during the shift into 2nd (on the 740, shift into 3rd on the 754).  Other people have the lockup occur just before the shift to 2nd and therefore feel a distinct additional shift.  You should be able to figure out how your tranny is setup by playing with these facts while driving.

[Nick Badame Refrig/ACC]

Hi Brian,

When taking off from a stop, I feel 4 additional shifts in the trans. "feels like a 5 speed" but, I'm sure it's the lock-up.

And when at cruising speeds, when I let go of the peddle, the rpm's drop off.

Nick-

[DrivingMissLazy]

My 740 would drop out of lockup at about 15 mph. You could definitely tell as you immediately lost the action of the Jakes. I was in some mountains out west where I would have liked to have been able to keep it in lockup at a lower speed, but I never found anything east of the Mississippi where I would have needed it.
As I recall it was Brian that came up with the modification to keep it locked up and I think that would be an excellent mod to have.
Richard

[luvrbus]

Nick,if you want the hookup like Brian talks about you can get one off a fire truck at a wrecking yard as most had them,but regardless your Jake is going to release at the rpm where the man has it set where it is at 900 rpm or 600 rpm.mine is set at 700 rpm and you can down shift to keep the rpms up and the Jake engaged longer.

[TomC]

Nick- if your rpms are falling off when you take your foot off the accelerator at anything above about 30mph, then your lockup clutch is malfunctioning some how.  Under normal circumstances, you should get lock up in the top end of 2nd gear.  If you turn 2100 at 75 mph, then lockup should occur around 31mph and stayed locked up in 2,3,4.  If your lockup clutch is not staying locked up like it should, your Jake brakes will do very little for you.  Good Luck, TomC

[rip]

I'm with Richard.If there is a modification to keep the Jakes on longer,I would like to know who to contact.I was in the MTS. in Ca. and nearly lost my brakes.I was in second gear with my 748 tranny and the Jakes would go out at 1300 rpm's about 15 to 20 mph.When I finally found a place to pull over my front brakes your smoking and the temp was about 405 degrees.I had to keep the tranny in reverse until I could block up the front tires.Needless to say if someone can help with this problem I would like to know.           
       Don

[luvrbus]

Don, you just need to adjust your buffer switch the Jakes shouldn,t release  at 1300rpm it should be from 700 to 600 rpm

[DrivingMissLazy]

You should all remember that there are two different dropouts. One is tranny  and the other is Jake.

The Jake buffer switch should be adjusted so that it opens up the Jake circuit at about 25 rpm above low idle. In other words if your engine is set at 550 rpm (mine was) then the buffer switch should be adjusted to open at 575 rpm. This disables the Jakes at very low rpm. As Tom indicated in an earlier post, this is more important in the four strokes than in the 2 strokes since the Jakes will continue operating on the four strokes right down to idle speed.

On the DD's, the oil pressure drops so low, generally, that in the 7-800 rpm range the Jakes will drop out due to there not being enough oil pressure to hold the exhaust valves open in the Jake system.

When descending very steep grades, with the gear selector in first gear, the 740 will not lock up until you get to about 10-15 mph in first gear. At that point, the Jakes will start working and will continue working as long as you do not slow down enough to drop out of lock up.

The other problem I experienced was that if the speed increased to about 25 mph then the tranny would shift to 2nd gear and of course that was not desirable because you lost a lot of the higher rpm Jake action. So I would have to use brakes to slow down until the the tranny would shift back down to 1st gear.

Just my experience. It may not be the same for everybody.
Richard

[Nick Badame Refrig/ACC]

Nick,if you want the hookup like Brian talks about you can get one off a fire truck at a wrecking yard as most had them,but regardless your Jake is going to release at the rpm where the man has it set where it is at 900 rpm or 600 rpm.mine is set at 700 rpm and you can down shift to keep the rpms up and the Jake engaged longer.

Hi Luvrbus,

Brian is sending me his..  Nice Guy! Huh..

Nick-

[Nick Badame Refrig/ACC]

Brian, Tom, Richard,

Brian said, Other people have the lockup occur just before the shift to 2nd and therefore feel a distinct additional shift.

Is this the distint bang into 2nd gear I have when not heavy on the throttle?

Thanks
Nick-

[luvrbus]

Nick, i sure Brian told you to disengage the over ride before you stop because it will tear the flexplate if you forget

[Nick Badame Refrig/ACC]

Would it help to tye the selonoid into the buffer switch?

This way it would release when the jakes do.

??
Nick-

[rip]

I know little about jakes.I will be headed to the Twin Cities by Maple Groves for a few weeks if any one knows of a good shop.I have a 85 Prevost with an 8v92.
Thanks
Don

[belfert]

I know little about jakes.I will be headed to the Twin Cities by Maple Groves for a few weeks if any one knows of a good shop.I have a 85 Prevost with an 8v92.

Best bus repair shop in the Twin Cities is C&J Bus Repair in Bloomigton at 952-881-0034.