What is this on the sm465?
- Thread starter Jamesz
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PrairieDrifter
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It's a speedo adapter. Don't ask me what it does I have no clue
PrairieDrifter
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Pretty sure it's just a gear reduction inside. The speedo cable connects to that box.
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Like Mason stated, ratio adapter. Auto transmissions can have several different drive gears form the tail shaft, and lots of different driven gears. Many choices to match tire diameter and gear ratio.
The SM465 does not have the large driven gear hole like an auto trans. Speedo match is done with that ratio adapter. The ratio of the adapter is marked on it (hiding under the grease). Need a different adapter if you change tire size or axle gear ratio, to get the correct speedo reading.
The SM465 does not have the large driven gear hole like an auto trans. Speedo match is done with that ratio adapter. The ratio of the adapter is marked on it (hiding under the grease). Need a different adapter if you change tire size or axle gear ratio, to get the correct speedo reading.
PrairieDrifter
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Same for a 205?
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I know my 203 has an adapter. I don't have a 205, probably yes. Some gear/tire combos don't need an adapter, the match is good.
AuroraGirl
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77 k25, 78 k10
barrymattern
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Thought I'd add this pic to the mix – this is the ratio adapter on my SM465/NP205 setup. I had no idea what it was until recently when we were working on this project to swap out my TH350 with the SM465/NP205 combo. If it helps, the driven gear inside the NP205 also has different varieties with different spline counts that can swapped out to help adjust the ratios in addition to the ratio adaptor. I pulled this info below from https://ck5.com/forums/threads/speedo-gears-calibration-and-np205s.341741/
Speedometer Parts
GM 205 pencil gears have varying tooth counts, those are how the speedometer is adjusted. There is a letter stamped on the side dictating how many teeth the gear has:
H 18
J 19
K 20
L 21
M 22
The speedometer gear on the output shaft can't be substituted with another, they will physically interchange but the teeth are different heights and the pencil gear won't mesh with the wrong output shaft gear. Output shaft speedometer gear tooth counts below:
Early GM metal speedometer gear - 5 teeth
Red/Yellow GM/Dodge speedometer gear - 6 teeth
Clear Ford speedometer gear - 7 teeth
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AuroraGirl
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youre missing the spacers for your crossmember bolts
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AuroraGirl
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interesting how are 205's have the cable leave different sides. what is yours out of?
barrymattern
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I have the spacers on the passenger side (albeit, different sizes), but you're right, none on the driver's side – unless you're referring to different spacers? I was under the impression from other forum posts they may not be necessary, but could be useful if you needed to change the level of your trans/t-case, but I could be misinformed.
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barrymattern
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Yeah, I was surprised to see it on the other side in the pic above. I'm not sure what mine is out of as I bought it from someone already pulled from a truck – they didn't say what it was out of or what year. I've included a pic of the combo from when I received it, and from looking into the backup light connector it appears to be newer than an '81 (unless replaced) when searching on a new connector on LMC, item #2 at this link:
I'm assuming it's out of a 1-ton since NP208s came in 3/4 tons during that timeframe
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AuroraGirl
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but it has a fixed output, which i suppose someone could have changed over
I wonder if its a 1985 with synchronized internals
Whats the shape of the np205 to the adapter like? The figure 8 is the older one, the newer one should have a round interface to the np205
barrymattern
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I'm glad you're asking these questions because I've never had a good idea of what I have in terms of year, so this is helpful. Attached are some pics that show the full combo, the adapter from both sides, and the t-case on the adapter side. Do these help with identifying things?
