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Allison HT740 shift problem kurt 7-11-05  
I have a 1976 MCI-8 with a allison HT740. When I got it the seller said that it shifts faster than it should. By 35mph you are already in the last gear. I know in cars with auto trans there is a kick down that raises the shift points when you floor it. Does the allison tran work the same. Could you give me some info on this
Thanks Kurt
Re: Allison HT740 shift problem luis 2-11-08  
I have 1999 ht 740 on a mack truck engine star when trnny is in gear, if you have any information or diagarms please let me know thanks

Re: Allison HT740 shift problem Randy 7-20-05  
It sounds like your modolator is not working properly. First thing, you need to find out if it is a cable modulator or air modulator.
If it is a cable modulator it can be adjusted if it is not broken. Remove the end from the transmission, which is located on the left hand side (in your case the passenger side) just above the top of the oil pan about 2/3 of the way back. There will be a pin inside. Have someone step on the throttle to see if the pin moves in and out with the throttle. The engine may have to be running to do this. If the cable is not broken, then locate where the cable attaches to the throttle linkage. At full throttle you should be able to pull the end of the modulator cable about 1/8" past the throttle linkage.
If you have an air modulator. Remove the air cylinder. Apply shop air to the air inlet side of the air modulator. If any air leks by to the plunger side of the modulator, replace the modulator.
Hope this helps if there is something else you need to know feel free to call me at 715-273-3893.
Re: Allison HT740 shift problem Geoff Warren 2-1-13  
I have an HT740 bolted to a Cat C-10. The problem I have is the trans when it is running cool it shifts fine up and down, but when it gets hot it will not shift out of 2nd gear. Also when still operating in pre optimum temp will go into reverse but after it is running at full temp it will not operate in reverse.
Re: Allison HT740 shift problem mike miraglia 9-20-08  
We have an oshkosh mixer truck 2001

with a cat c-10 motor, we recently installed another engine (used) and now the tranny won't shift out of first unless it is driven about 5-6 mph. then it will shift thru the gears ok.

the engine is rated at the same rpm as the old one. we have tried changing the trans fluid and filter and also the governor screen. installed dexron 3
fluid as recomended.

the engine runs great.

checked all wiring connections to the ecm, speed sensor and cleaned.

could there be a need to change any programming in the new motors ecm?
Re: Allison HT740 shift problem Yugani 6-17-09  
I have ht 740 allison. Serviced the gearbox by dropping the valve body and clean out journals and passage ways. slugg was turning hard. replaced the valve body and now I dont have 3 and 4th gear. no matter revs. what could be the problem. stripped it again and cant find any blogages.
Re: Allison HT740 shift problem SGT. Covellone, M. 3-4-10  
We have a Freightliner M916A1 with a Detroit diesel series 60 motor and a HT-740 trans. I recieved the truck for a tranny service. simple drain & fill and a filter/pick up change. when i drove the truck in it was fine, but now it wont engage into gear. it operates as if its empty, it reves up and she bairley moves, if any at all. ive dissasembled and reassembled it 3 times to ensure ive done nothing wrong. in the ARMY we use 15-40w for the fluid, its fresh and full. the TM'S (tech. manual) dont address this issue, it only advises a trans. replacement. are there line pressure fittings i can check before i take the extreme route and pull the whole thing???
Re: Allison HT740 shift problem Asst Chief Michael Papke 8-24-11  
HT-740 with air modulator.At full throttle this trans hunts between high gear and the next gear down.Otherwise it shifts and pulls fine.
Thanks so much for any help you can give.
Re: Allison HT740 shift problem SSG Rafael Garza IV 3-14-10  
I have a M978 with a Detroit Diesal Engine hooked up to a 740 Trans. It wont shift out of 1st gear. What is the theory behind a trans lock-up solniod? I am gonna verify that the modgulator is working properly. We have air supplied to it. Thank you for your support...
Re: Allison HT740 shift problem larry price 4-30-14  
Hot will not shift auto & will not go in reverse
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