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transmission help please!

  #1  
Old 02-05-2013, 09:47 PM
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Default transmission help please!

I have an '89 K1500 Cheyenne 4x4 with a tired 305 and the 5-speed manual HM-117 transmission. I am rebuilding a '98 350 Vortec to replace the 305, and think that I should upgrade the transmission for the Vortec's increased power and tourqe. I don't plan to drive this truck hard, but reliability and the ability to pull a trailer is essential.
Can anyone suggest a transmission upgrade that will bolt right in??
Any reply greatly appreciated, Thank you, Kevin
 
  #2  
Old 02-05-2013, 10:20 PM
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Do not believe there is a bolt in upgrade. Also I don't recall if the NV3500 has a higher torque capacity than your current trans. The NV4500 can handle much more but has a separate bell housing and takes a different input gear on the transfer case.

Now what I looked up shows the HM-117 to be a 4speed manual.
If you have a 5spd it is something else.
Do you know what your RPO code is?
 
  #3  
Old 02-06-2013, 10:48 AM
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Dan, thank you for your reply.
I made an error in my initial post. The transmission is in my truck is the HM-290 RPO MG5 (NOT the HM-117). My understanding is that the HM-290 is rated for 300 ft-lbs of tourqe. Maybe it can handle the Vortec, as I don't drive hard. Currently the transmission is working fine and there have never been problems with it.
I don't mind if I have to change the transfer case.
I'm hoping that there is a Chevrolet or GMC truck out there, any model year, that I can salvage the transmission (and transfer case if needed) and bolt them into my 1989 chassis.
 
  #4  
Old 02-07-2013, 08:24 AM
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Those transmission are sensitive to having the proper quality fluid in them.
I'd recommend draining and filling it now if you don't know the maintenance history.
 
  #5  
Old 02-08-2013, 01:43 PM
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Thanks for that Dan, I do know the transmissions service history; I've driven the truck daily for roughly the last 15 years and the transmission fluid is correct.
Chances are the transmission will be fine behind the rebuilt Vortec, but I would prefer to put in a transmission that's known to be tough.
 
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