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I just bought a 1980 GMC K10 and iM having a.

Tiny
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  • MEMBER
  • 1980 GMC TRUCK
  • 56,000 MILES
I just bought a 1980 gmc K10 and im having a hard time finding out exactly what parts I have for it from the codes stamped in the cast of the transmission, transfercase, and both diferentials, the front diff is a 10 bolt, theres a code that says 3030376 or 3030378, just unsure about the last number, it also has a GM7 on it, the rear is a 12 bolt and has GM12 N 9969, the transmission says AE 50-99404, and I cant find anything on the transfercase but I know its a parttime 4x4, I believe its a NP205, if its possible to tell me which transmission (SM465 I believe) and what gear ratios I have id very much appreciate it, thanks.
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Sunday, December 16th, 2012 AT 5:08 AM

12 Replies

Tiny
HMAC300
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Axles used paper tags for the rear ends, then so look on glove box it may give detail there. If you have a big pan on trans it is probably a thm 400 if it has a throttle cable going to it on lh side it's a thm350 axle ratios will be on the gears like 14-30 etc normally ring gear. Tcase shold have a metal tag on it
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Sunday, December 16th, 2012 AT 5:10 PM
Tiny
JESSESANDBERG
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It has a 4 speed manual transmission, theres nothing in the glovebox and I cant see anything on the chart on the door, the AE-5099404 is in the transfercase not the transmission sorry. I would of liked to find out what it may have for ratios without pulling the diff plate but if I have to I will, thanks.
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Sunday, December 16th, 2012 AT 9:33 PM
Tiny
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Seeif there is a tagon the glove box door or drivers side with a whole bunch of numbers that would give better tags to look up. If it's a 4 speed it is eitehr a saginaw or muncie, the muncie would have tehe shifter coming through the floor directl to the trans with nolinkage outside. Of trans. The 4 speed if a muncie would have a very low 1st gear, almost useless on the street. If this is a pickup it will probably have a muncie 110mm trans.
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Sunday, December 16th, 2012 AT 10:22 PM
Tiny
JESSESANDBERG
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Ya a very low first gear, so probably a 465 then
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Sunday, December 16th, 2012 AT 10:47 PM
Tiny
HMAC300
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If the shifter is in center it's a110mm muncie trans. Here I found some stuff make sure you pay attention to area I have pointed out in arrows. That is front axle ratio and other page is rear axle ratio with the esception of positraction. Good luck on finding tape stripes for frt axle id.
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Sunday, December 16th, 2012 AT 11:02 PM
Tiny
HMAC300
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Btw to prevent tcase windup so you don't have to put in reverse to shift out of 4wd the gear ratios should be about the same. Also I could not find any id for tcases. You might try googling it.
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Sunday, December 16th, 2012 AT 11:03 PM
Tiny
JESSESANDBERG
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Oh ok thank you, also, the clutch pedal sticks to the floor when is pushed in and releases a second later which makes it a little hard to shift without jumping a little, I just greased the bellcrank zerk and that didnt help, could it just be the clutch release spring or could it be something else?
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Sunday, December 16th, 2012 AT 11:11 PM
Tiny
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Yu greased the cross shaft y ou mean? Check your linkage for binding as the bushing in cross shaft wear out also check for abent release arm /fork.
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Sunday, December 16th, 2012 AT 11:13 PM
Tiny
JESSESANDBERG
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And when I put it in reverse there sounds like a whine, sort of like a power steering pump with no fluid but alot quiter, any ideas?
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Sunday, December 16th, 2012 AT 11:14 PM
Tiny
JESSESANDBERG
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What exactly is a release arm? And where could I find it? Outside the cab underneath or inside the cab behind the dash cluster?
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Sunday, December 16th, 2012 AT 11:33 PM
Tiny
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It connects to the throwout bearing in the clutch housing. What your adjustment link connects to
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Sunday, December 16th, 2012 AT 11:35 PM
Tiny
JESSESANDBERG
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Ok, il go crawl under and give a look, is there anything else I should look for or may want to take a look at?
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Sunday, December 16th, 2012 AT 11:43 PM

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