Okay, Last summer I asked about the ability to "force" lockup of the torque converter while in 1st or 2nd. The reason was while climbing mountains when the transmission was in 1st or 2nd the torque converter unlocks and when that happens the engine temperature rapidly climbs. I had several hills I had to climb in 1st gear not because I didn't have enough power in 2nd, but because the temp guage was climbing too fast from all the extra transmission heat. Several on the board and locally recommended hooking up the main pump pressure port to the torque converter lockup port externally by way of a hydraulic solenoid valve. I thought great, no problem and even got the diagram of the underneath side of the ht754 so I could make sure I knew what the main and torque converter lockup ports were. Everything is flowing smoothly at this point. Now on to the problem... As you guessed it doesn't work.
So, what I did was hookup the solenoid to the dash by way of an electric switch (standard stuff) and mounted the solenoid to the tranny and connected the solenoid to the main and lockup ports using 1/4" copper. Well, after setting it up and making sure the solenoid worked (by sound) I took it for a drive and nothing happens when I turn on the switch. This evening I set about troubleshooting this and have completed the following steps in trying to troubleshoot the problem:
1) Made sure Solenoid works (by sound) (it sounded like it did, so moved on to next step)
2) Tore apart solenoid and cleaned out every passage and tested on shop air (no problems found)
3) Remounted on bus and left output port (lockup side) of solenoid undone. Started motor and tested (works GREAT!)
4) Reconnected lockup side and tested again... Still nothing.
So what I'd like to know is if anyone has actually done this "mod" and if so what tranny did you do it on?
One last piece of information... The ports on the tranny are 1/8 npt and the solenoid and lines are all 1/4" ports and according the the diagram I got from C&J Bus (JD Dickenson) the ports I connected to are correct.
Any ideas?
-- PS. I should also add that the transmission was overhauled by a competent local builder (not DD) less than 10,000 miles ago
Brian;
Put a pressure guage in the main pressure port and verify that you have pressure there if not look for another port.
Don
Thanks for the idea Don. I guess I just assumed I had plenty of pressure since the running test I made caused an impressive display of tranny fluid to shoot out at high velocity. However, doesn't hurt to test the true pressure. I'll see if I can find a pressure gauge to test with. I seem to remember that the main output pressure runs in the 180-190 lbs when in forward. Does this number sound right?
Brian- couple of things. I've heard that only an electronic transmission can get lockup in 1st gear. I assume you had pulled the shift lever to first when you were climbing and didn't have lockup. Another way can work, but only if you have an air throttle with an air operated throttle sensor to the transmission. You can get lock up if you put a solenoid with a dump valve so when you activate it, it dumps the air to the throttle sensor and the transmission thinks you're in no fuel position, where the transmission will lock up when in 1st position.
I have a V730 with an air throttle sensor, and when I get into 2nd torque converter, just slow a bit and pull it to 1st with my foot on the floor. When I'm just about up against the governor, I pull up on the throttle about an inch and you can feel the torque converter bump into engagement. Then just go up the hill at the 34mph without the tranny overheating. You are right that if you can keep in torque converter lockup mode, the trans won't heat everything up. Good Luck, TomC
Brian,
There has to be a valve inside the transmission that allows the pressure in the lock-up chamber to release when the transmission comes out of lock-up mode. If this valve is open (transmission in non lock-up mode), wouldn't this let the pressure you are adding simply flow through the lock-up chamber? Jack
Hi Jack,
I had assumed the same thing initially, but was told the port opening to release lockup was smaller than what could be put back in by this external means and therefore would keep the torque converter in lockup. This may not be true given my experience so far, but I'm hoping I can overcome this problem to simplify my life a little. If I can't get this to work then I'm moving on to radiator misters. Of course, I REALLY want this to work since it will help me significantly on the downgrades. -- We tend to stray off the beaten path and some of those 6% grades with 20 mph curves are a beast when the tranny drops lockup!
Well, if you want to know about misters, there sure is lots of information here about them. LOL
BTW I really missed the first gear lockup going down some of the passes in California. Even the Jake would not work.
Richard
Quote from: Brian Diehl on June 13, 2006, 06:38:58 AM
Hi Jack,
I had assumed the same thing initially, but was told the port opening to release lockup was smaller than what could be put back in by this external means and therefore would keep the torque converter in lockup. This may not be true given my experience so far, but I'm hoping I can overcome this problem to simplify my life a little. If I can't get this to work then I'm moving on to radiator misters. Of course, I REALLY want this to work since it will help me significantly on the downgrades. -- We tend to stray off the beaten path and some of those 6% grades with 20 mph curves are a beast when the tranny drops lockup!
Whether or not you have an electronic transmission, when you pull the gear selector down to 1st gear you should get lock up at least on deceleration so that the transmission would be locked up as low as about 15 mph. On my V730 it does that, and since it is the same transmission family, should also work with the HT754CR (it is either a CR-Close Ratio, or a DR-Deep Ratio. Since you have the 754, that was only availabe as the CR. The DR was a straight HT750). Good Luck, TomC
I don't get lockup while having the gear selector in 1st with no throttle. If I had that half my problems would be resolved.
Anyone buy the HT740-HT750 mechanics manual? If so, was it good enough I should buy it to try and help figure out this problem?
Tom my 740 would stay locked up till I got down to about 15 mph. However that was really too fast for some of the curves and the grades.
Richard
Richard- I admit, that for speeds under 15mph, a 10 speed transmission will give you the most control. But what percentage of the time are we down at that speed in an off road or severe road condition? I'll still stick with an Allison.
All I know is that when the gear shift lever is pulled down to first you should get lock up on no accelerator pedal position. If not, you'll have to consult Allison. Good Luck, TomC
I just tested the pressure and I have 160psi in neutral at cold startup on the "main" port.
I'm going to post some pictures of my setup so you can see how I have it configured.
Sorry the pictures are a little fuzzy. I couldn't get my camera to focus in the semi-darkness under the bus.
Brian,
First, please don't take this as being cynical, but are you sure you are connected to the lock-up port? Also, I see you used 1/4" copper tubing and fittings, but what is the diameter of the orfice in the solenoid. Perhaps the orifice is to small and not allowing enough fluid to override the vale in the transmission. You might try opening the line from the solenoid, start the engine, and engergize the solenoid. See how much fluid come out. Hope this helps, Jack
Thanks for the reply Jack. I have confirmed a very high volume of oil at very high pressure comes out the solenoid when energized with the engine started and the tranny in neutral. However, I am not 100% convinced I'm connected to the lockup port on the tranny. Though, from my initial post you can see that I think I'm on the right port. The solenoid uses 1/4" passages.
Does anyone have access to a manual that would show the lockup port?
brian;
Now what you need to do is along with the valve you have, install a versa valve or simler valve. You will plum from the electric valve to the versa valve in, from the out to the lockup port from the ex port back to the trans pan. If you don't the lock up clutch wont release. Use #6 hose as #4 wont flow enought oil in either driction. You can also hook your electrial up to your jake brakes so lockup will stay ingaged intill your jakes turn off.
Hope this helps
Don
Hi Don,
I'm a little confused by your post. Right now I don't know if I'm even on the lockup port for the output from the "main" port. Do you think the port I'm connected to is right? If I am on the right port, any ideas on why I'm not getting lockup?
Next, what is a "versa valve"? Next, what/where is the "ex port"?
I'm using the 1/4" copper pipe on the current install. How does that compare to #6 (or #4)?
Do you have some sort of diagram that would help me visualize the installation you are suggesting?
Brian;
The versa valve is a shuttle valve that will move one way or the other depending on if you want pressure or to exhaust the pressure.
I was looking for my diagram but could not find it. Several moves and I still have some things in storage, things do get lost over the years. I will try to find some part numbers and a diagram for you. Might take me a few day's to come up with it though.
Not shure on how to draw a picture on the computer and I don't have a scanner. I'll come up with something for you.
Don
---- SOLVED ----
I am VERY happy to report that I've got the torque converter lockup override WORKING!!!!! Yes, I am very excited about it. The funny thing is the lockup port I found by trial and error is not listed in any of the manual pages I have.
The lockup override works very nicely. As soon as I'm moving fast enough to be solidy in 1st gear I can turn on the override and the lockup happens immediately in 1st. Then the normal shift to 2nd happens without me having to disengage the lockup. The shift from 2nd to 3rd, 3rd to 4th, and 4th to 5th happen normally as well. Of course, lockup happens regularly at the end of 2nd gear so the shifts in 3rd and 4th are no different. I will probably use this override even when I'm not in the mountains as it makes the acceleration through 2nd gear much quicker and I'm sure more energy efficient. However, there is a very large RPM spread between 1st and 2nd so I probably won't use lockup override regularly in 1st during normal driving. The lockup does work at all speeds so of course I have to disengage the override before coming to a stop so I don't kill the engine.
The lockup port ended up being the port right next to the "main" output. This is the port immediately next to the raised (lower physically) section containing the main pressure port in the center of the trannsmission.
Thank you everyone for your help and ideas on this problem. I am just pleased as all get out that it now works exactly as it was described to work!
Brian- as you discovered, the ratio gap between 1st and 2nd is very large. Allison geared it this way with the slip of the torque converter in mind. I would highly recommend that you NOT use the manual lockup all the time, rather only when you are in that gear and especially not from 1st to 2nd locked up. Remember that the lockup clutch on the torque converter is just a single plate dry clutch that is holding together all of the torque the engine is passing through. Just my recommendation, you'll do it your way (and hoping nothing will happen). Good Luck, TomC
So.... Can I do this on my 643 ?
Should since the MT643 is just a smaller version of the HT740. Good Luck, TomC
Brian,
CONGRATS!! Glad to see you got it working. So how did you firgure out which port was the lock-up port? Jack
Tom, Thanks for the advice on the internals of the lockup. I'll definintely not use the lockup as part of the 1st to 2nd shift unless absolutely necessary given the information you've given me. Very valuable advise for sure!
Jack, I found the port by simple trial and error. On the non-retarder based HT740 and HT750 series transmissions there are only 4 ports on the bottom of the tranny up by the torque converter. The pictures I had from Detriot Diesel showed some models using the outermost port for torque converter lockup and when compared to my tranny it was the most closely identical to my tranny that I picked. However, the outermost port was not the lockup. I then saw some models had the lockup port next to the outermost port. I decided I had nothing to lose to try that port. It didn't work either. I was about to tear everything off of the tranny when I decided I had nothing left to do but test the 3rd and final port. I decided to try and was immediately glad I did. In the end I think I have a slightly different tranny configuration than was has been published in the standard Allison manuals. I don't know why, just given what I've experienece with DD on the phone and such I've got a "wierd" tranny to deal with.
Of course the good news is I got it to do what I really wanted it to.
Quote from: Brian Diehl on June 16, 2006, 05:51:52 AM
Tom, Thanks for the advice on the internals of the lockup. I'll definintely not use the lockup as part of the 1st to 2nd shift unless absolutely necessary given the information you've given me. Very valuable advise for sure!
Jack, I found the port by simple trial and error. On the non-retarder based HT740 and HT750 series transmissions there are only 4 ports on the bottom of the tranny up by the torque converter. The pictures I had from Detriot Diesel showed some models using the outermost port for torque converter lockup and when compared to my tranny it was the most closely identical to my tranny that I picked. However, the outermost port was not the lockup. I then saw some models had the lockup port next to the outermost port. I decided I had nothing to lose to try that port. It didn't work either. I was about to tear everything off of the tranny when I decided I had nothing left to do but test the 3rd and final port. I decided to try and was immediately glad I did. In the end I think I have a slightly different tranny configuration than was has been published in the standard Allison manuals. I don't know why, just given what I've experienece with DD on the phone and such I've got a "wierd" tranny to deal with.
Of course the good news is I got it to do what I really wanted it to.
Brian,
Is there a chance you could take pictures of what you've done and maybe write it up in a text form so that we could put it in the archives and the help section?
Thanks,
Dallas
Brian;
Glad you found the port you needed. Nice pic's. 1/4" and #6 are the same size.
Don
Brian,
I would like to see a photo of the area where the ports are. I am planning to put a pressure switch in the lock-up port on our 740 that will shut off my Jake (not installed yet) when the torque converter comes out of lock-up mode. Thanks, Jack
Hey guys,
Sure, I can write something up. I'll take a few pictures of the final install and put something together. How should I post it for all to see?
BTW, I'll be out much of the weekend, so I don't think I'll get to this until next week.
-Brian
Put it on your website and post the link. Then you won't lose it when something happens to board.
Good Idea Craig. I'll take that approach!
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?
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fhome.earthlink.net%2F%7Ediehls0792%2F2006_0731_T-C-Lockup_02.jpeg&hash=8bf0b8b33aa4d006d847b58295a5d73d92219515)
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
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
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-
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
Quote from: Don Fairchild on June 16, 2006, 04:57:58 PM
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.
Quote from: TomC on August 01, 2006, 08:17:27 AM
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.
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
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.
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
Quote from: TomC on August 01, 2006, 08:17:27 AM
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
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