Author Topic: gear ratios for a ht70  (Read 2875 times)

Offline artglass

  • Jr. Member
  • **
  • Posts: 78
gear ratios for a ht70
« on: May 19, 2016, 11:21:51 PM »
thinking of going to a 8v92 ta with either a ht754 or a ht 70 transmissions anyone have any gear ratios on the ht 70 cant seam to find any thing online, anyone know the length on a ht 70, read it does have a overdrive


Offline CrabbyMilton

  • Hero Member
  • *****
  • Posts: 1059
Re: gear ratios for a ht70
« Reply #2 on: May 20, 2016, 05:28:31 AM »
Wow Cheesie that is a lot of interesting info there. I know that I have tons of ALLISON brochures in cases in the basement.

Offline HB of CJ

  • Hero Member
  • *****
  • Posts: 1765
Thank You chessie: ...
« Reply #3 on: May 20, 2016, 03:42:38 PM »
You nailed it and thank you.  My memory would have been close, but not quite correct.  HB  :)

Offline TomC

  • Hero Member
  • *****
  • Posts: 8651
Re: gear ratios for a ht70
« Reply #4 on: May 20, 2016, 09:14:58 PM »
If it were me-I'd opt for a 8V-92TA mechanical with 9G90 injectors 450hp @ 1350lb/ft torque and the Allison HT740 4spd Automatic. This is the most reliable bullet proof combination you can have. Except maybe for my truck engine of Caterpillar 3406B mechanical and HT740. You'll see hot rod trucks using the HT740 all the time-rarely the HT754. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline TomC

  • Hero Member
  • *****
  • Posts: 8651
Re: gear ratios for a ht70
« Reply #5 on: May 20, 2016, 09:17:22 PM »
Even though the HT70 has an overdrive, it is an obsolete transmission, and it is only rated to 350hp and 888lb/ft torque. Stick with the HT740 or 754. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline TomC

  • Hero Member
  • *****
  • Posts: 8651
Re: gear ratios for a ht70
« Reply #6 on: May 20, 2016, 09:19:49 PM »
My truck with HT740 and 3.55 rear ratio with 11R24.5 tires (476rpm) will give me at 65 1830rpm. Or if I want to really get good mileage, slow to 1600rpm that will be a cruise of 57mph. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline artglass

  • Jr. Member
  • **
  • Posts: 78
Re: gear ratios for a ht70
« Reply #7 on: May 26, 2016, 11:04:18 AM »
thanks for the info didn't realize they were  couldn't handle the torque

Online chessie4905

  • Hero Member
  • *****
  • Posts: 2825
Re: gear ratios for a ht70
« Reply #8 on: May 26, 2016, 11:34:54 AM »
they were under rated like the V730, but in severe commercial service. Probably hold up ok in our use.
GMC h8h 649#028 (4905)
Pennsylvania-central

Online luvrbus

  • Hero Member
  • *****
  • Posts: 19540
Re: gear ratios for a ht70
« Reply #9 on: May 26, 2016, 12:07:07 PM »
The old HT 70 most were wet torque converters,I have a friend his MCI 7 has a HT 70 with a wet torque converter from the factory 
Life is short drink the good wine first

Offline CrabbyMilton

  • Hero Member
  • *****
  • Posts: 1059
Re: gear ratios for a ht70
« Reply #10 on: May 26, 2016, 01:01:46 PM »
Please explain what a wet torque converter is. I thought they all were in respect that they act as turbines.

Offline TomC

  • Hero Member
  • *****
  • Posts: 8651
Re: gear ratios for a ht70
« Reply #11 on: May 26, 2016, 05:19:20 PM »
Wet torque converters is where the bell housing and starter is sealed and the trans fluid can drain through the bell housing. V730 is that way.
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Online Scott & Heather

  • Scott & Heather's buses: MCI-9 & MCI-102
  • Hero Member
  • *****
  • Posts: 4250
  • MCI-9 & MCI-102
    • Fresh Day Music
Re: gear ratios for a ht70
« Reply #12 on: May 27, 2016, 03:46:54 AM »
So how do you guys get 740's to shift nice? My 9 has a 740, and it shifts dumb (way too early in the rpm bands) and it definitely doesn't shift nice and smooth, it kicks into gear and shudders the coach slightly. I honestly won't miss it when the new owners take delivery in June. My 748 shifts so nice and smooth and shifts much higher in the rpm range. I never have to tell it what to do, just press the "D" button and off we go. I would much prefer the reliable simple 740 over the finicky ATEC 748 but I just can't imagine going back. Am I missing something?


Sent from my iPhone using Tapatalk
Scott & Heather
1984 MCI 9 6V92-turbo with 9 inch roof raise (SOLD)
1992 MCI 102C3 8v92-turbo with 8 inch roof raise CURRENT HOME
Click link for 900 photos of our 1st bus conversion:
https://goo.gl/photos/GVtNRniG2RBXPuXW9

Online luvrbus

  • Hero Member
  • *****
  • Posts: 19540
Re: gear ratios for a ht70
« Reply #13 on: May 27, 2016, 05:39:44 AM »
Shift points, modulator and trimmer springs adjustments make a 740 shift right, the 740 and 748 are basically the same transmissions on the 748 the fluid control is controlled by the electronic solenoids 
Life is short drink the good wine first

Offline TomC

  • Hero Member
  • *****
  • Posts: 8651
Re: gear ratios for a ht70
« Reply #14 on: May 27, 2016, 08:45:00 AM »
The HT740 that was installed behind my Cat 3406B is what they call a soft shift. The way it shifts is-1st gear is all torque converter, then to 2nd still in torque converter, then the torque converter locks up in 2nd. When it shifts to 3rd the torque converter unlocks during shifting then locks up again once it is in 3rd. Does the same from 3rd to 4th. I also have a manual switch to lock up the torque converter if I want continuous lockup from 1st. It shifts very smoothly. If your transmission is shifting at too low an RPM, maybe a simple adjustment on the throttle modulator is all that's needed. The modulator should be in full open position at full throttle. Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.