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5LM60, HM290, Getrag HELP

Benfromsac

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Benfromsac New Member

Benfromsac

Posted
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I've just recently purchased a 1989 GMC Sierra K2500 LB to replace my 1988 K1500 SB that started losing gears one by one. 2 months later, the tranny in the newer truck lost reverse. I can't afford to buy a 3rd truck so I have to repair it myself. Well, like most guys with these transmissions, I went thru hell trying to identify exactly which tranny I have. I'm 99% sure I have the 5LM60. My problem is that I've got the tranny almost fully taken apart, but I can't seem to remove the gear clusters out of the case and I can't find any info on it online to help me disassemble it. The diagrams for "Getrag 290" or "HM290" show slightly different internals so I'm stuck. Can someone please help me figure out how to pull the main shaft from the rear half of the case so i can replace the shattered syncro on the 5th gear/reverse rail? If someone could post photos of a few pages from a factory manual or similar, that would be awesome! Let me know if you need more info from me. Thank you in advance.

barry G Senior Enthusiast

barry G

Posted
Posted

I looked for nv3500 some years ago.

found this:

 

 

 

this one talks a lot, but you can skip around to what you want.

several videos, same guys.

gets into many details.

 

 

my own advice..

get a real shifter, billet base...no more rebuilds after that.

core shifters offers hurst in random intervals. those are the best.

 

when all is good, you should be breaking the factory transmission mount into pieces.

my own truck broke frame pieces before never losing the tranny in any gear... must have taken 8 tons or so.

 

watch out for the quiet ones too...

check for "big ends" on the shaft. You'll know you got the v8 version if you are unsure.

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