HT754CRD Lockup override question -- SOLVED

[Brian Diehl]

I've created a page on my website (http://home.earthlink.net/~diehls0792/) that shows and describes how I setup my lockup override.  The direct link to the page is http://home.earthlink.net/~diehls0792/HT754TorqueConverterLockup.html

Jack, does this give you enough to get started on your bus?

[Buffalo SpaceShip]

Holy cow, looks like I joined MAK after this thread. I'm sooo glad you posted an update and I saw it. Brian, you're a bootstrap-engineering busnut pioneer. Wow. And you've made your coach sooo much safer, too. Bravo!

Living in CO, I really want to do this to my V730. Your "blazing the trail" has given me the confidence to give it a shot.

Thanks immensely to you and the fellow busnuts (and industry folks) that has given success to this project,
(a different) Brian

[JackConrad]

Yes it does.  Thanks Brian.  I found a NC pressure switch tha opens at 50 PSI. According to my Allison manual, lock up pressure should be with 15 PSI of line pressure which is around 175 PSI. I will install the switch and confirm its operation with a test light before wiring it into my jake brake circuit. The NC 4 PSI switch I installed in the air throttle line works great. It opens the contacts just before the govenor comes off idle.  Jack

[ChuckMC8]

My powerplant donor, 1980 American-Lafrance Fire pumper truck has this installed from the factory. It is a HT740D.The purpose is to lock up the converter when the pump is running. It has a switch beside the gear shifter to enable the lockup. My trans guy told me that there are 2 solenoids, one is NO and the other is NC. He said (IIRC) that only one is needed to make the lockup and the other was a saftey circuit that was mandated after mech failure caused a firefighter to be injured.
I can send more photos or part #'s if anyone is interested-

[TomC]

On the V730, if you have an air throttle with air throttle sensor, you can just put a dump solenoid in line to make the transmission think it is in the no throttle position, then it will stay locked up down to idle.  Good Luck, TomC

[mdainsd]

Brian;

Glad you found the port you needed. Nice pic's. 1/4" and #6 are the same size.

Don

The #4, #6 etc come from the military AN standards for hydraulic tubing and fittings. In the standard they are called out as "dash" numbers, i.e, -4 and -6. The number equates to the number or 1/16ths of an inch in the ID of the tubing/fitting. So a -4 (or number 4 as some call it) is 4 X 1/16" or 1/4" in ID. A -6 is 3/8" in ID. This goes way up in sizes but the largest you usually see it the -16 stuff which is 1" in ID. Hope this helps.

[Buffalo SpaceShip]

On the V730, if you have an air throttle with air throttle sensor, you can just put a dump solenoid in line to make the transmission think it is in the no throttle position, then it will stay locked up down to idle.  Good Luck, TomC

Thanks, Tom. I do have an air throttle on the 4108, but have no idea about the throttle sensor. The V730 wasn't stock with the coach, so I'll have to see what was done to the tranny at install.

I'll pull out the old service manual and see if I can determine if it has one.

If it does... and I put in a dump solenoid, when driving, I:
1) start climbing or descending in 2nd range, un-locked,
2) pull it into first range
3) dump the air throttle... and it'll lock right up??

Sounds too good to be true, but I hope you're right. The airline for the throttle runs right under the driver, so it could be an easy install! I could probably test it out with a ball valve, eh?

Thanks so much for the info!
Brian B.

[ChuckMC8]

Wow! I had to look back to find this thread. I started to make a new topic, but since this is so interconnected and there is a photo of my setup already on this thread, I'll add it on here. On initial freeway test, I beleive that my converter isn't locking up in 4th gear. (HT740D)according to my tachometer, my engine is turning 2300 rpm @ 65 MPH. Old engine would run nearly 80mph at 2300.
  If you will look back in this thread and check out my trans has two solenoids that were installed (I suppose at the factory) to lock up the converter when the truck was pumping water. (was in a firetruck)
  Anyone know if I have to power the solenoids to make the lockup work? And if so, do I have to manualy control the lockup all the time?
  What happens if I wire the solenoids and flip on the switch at 2000 rpm in 4th gear? IS something Baaaaadddd gonna happen?

it's always something. So, I guess if it wasnt this, it would be something else. Otherwise, new eng/trans does fine. Thanks for the help on the other questions (air throttle, etc).

  thanks in advance

[Stan]

Brian:  In the grand scheme of things, an  Allison manual is not very expensive. I can't imagine trying to modify something as complicated as an Allison (and the damage I might do) without the book and all the flow diagrams.  My 740 manual went with the bus with the 740 transmission so I can't offer any help other than to suggest that you get a manual.  I think you would save a lot of time and effort if you have the info to work with. You are well aware that a lot of info provided on BBS is not correct, and although well meaning,  can steer you in the wrong direction.

[TomC]

Brian- some of the HT's were programmed to shift first into converter then into lockup at every gear.  So instead of 1C-2C-2L-3L-4L you had 1C-2C-2L-3C-3L-4C-4L- (5C-5L if you have a HT754CR).  It was done to keep the engine revved up-especially for trucks, and maybe on your firetruck for a bit more performance.  But now, none of the world transmissions offer that since the newer Diesels with electronic fuel injection have a much fatter torque curve.  As far as locking up the converter, I don't think it would matter when you do it.  The worse that could happen is that you forget to unlock it when coming to a stop and stall the engine.  By using my method of dumping the throttle sensor, you wouldn't have that problem of stalling, since the converter would release when it gets to idle.  Good Luck, TomC

[JackConrad]

On the V730, if you have an air throttle with air throttle sensor, you can just put a dump solenoid in line to make the transmission think it is in the no throttle position, then it will stay locked up down to idle. Good Luck, TomC

Tom,
   By "air throttle sensor", are you referring to the air operated modulator on the transmission?  Will this method also work on a 740 transmission equipped with an air throttle and air operated modulator valve?   Jack

[TomC]

Jack- I'm guessing that it should since the V730 is just a HT740 without 1st gear.  So it should perform the same.  Good Luck, TomC