Np208 Refurb Advice

[Frankenchevy]

This is a tangent of an existing thread about harmonic vibration.

Sometimes to shift from 2wd to 4Hi and Lo, I’ll need to be in neutral and allow the vehicle to roll back or forward about an inch to ease the t-case lever through the ranges. Is this normal or indicative of needing to replace the shift forks?

Additionally, I think my slip yoke is sticking out too far (3-3/16”).

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My concern is that operating the truck with this condition may have worn any parts related to axial play or yoke runout. If I do take the t-case apart, what parts are recommended to be replaced as a general refurbishment. I was guessing the rear most bearing on the output shaft, but not sure what else to possibly look at.

 

[yevgenievich]

depends on the total length, but looks like might be too much. Usually 4hi should not have engagement issues. On my 241c switching to 4LO and back likes to have a bit of a roll back/forward

 

[bucket]

The prop shaft could stand to be a little longer, but it's not as bad as it looks. The output shaft protrudes rather far past the extension housing.

Every 208 and 241 I have run, you could easily shift between 2hi and 4hi with no trouble at all. In gear at any speed. 4low normally just requires being in neutral.

 

[Frankenchevy]

The prop shaft could stand to be a little longer, but it's not as bad as it looks. The output shaft protrudes rather far past the extension housing.

Every 208 and 241 I have run, you could easily shift between 2hi and 4hi with no trouble at all. In gear at any speed. 4low normally just requires being in neutral.

Just to clarify, the output shaft should protrude rather far past the extension housing? Mine sits back about flush with the seal or maybe a bit inside iirc.

 

[Frankenchevy]

depends on the total length, but looks like might be too much. Usually 4hi should not have engagement issues. On my 241c switching to 4LO and back likes to have a bit of a roll back/forward

Would that be a matter of replacing shift forks or something else?

 

[bucket]

Just to clarify, the output shaft should protrude rather far past the extension housing? Mine sits back about flush with the seal or maybe a bit inside iirc.

Yeah, about this far:

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[Blue Ox]

That looks like the yoke hangs way too far out to me. Keep in mind that it rides in a bushing in the tail housing. Plus more spline engagement wouldn't hurt. When I get to the shop tomorrow I'll dig up the Gear Vendors instructions. They're pretty specific about how to measure it. I'll also take a ruler to mine and see how much space there is.

The main weak point I'm familiar with in the 208 is the welded planetary carrier likes to crack. I extended the welds on mine to help avoid the flexing at the ends of the welds that tends to create stress riser.

 

[bucket]

It does look like the shaft could stand to be about 1.25" longer.

 

[Craig 85]

This is for the guys that didn't read the same thread about his harmonic vibration.

My yoke measures 2 13/16" with the 3" lift. It moved out about 1/2" after the lift, so it would have originally been 2 9/16". FYI my drive shaft is 56 1/2" from center to center on the U-joint. I don't know if my 205 is the same length as a 208. This picture is before I did the lift.

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[Frankenchevy]

This is for the guys that didn't read the same thread about his harmonic vibration.

My yoke measures 2 13/16" with the 3" lift. It moved out about 1/2" after the lift, so it would have originally been 2 9/16". FYI my drive shaft is 56 1/2" from center to center on the U-joint. I don't know if my 205 is the same length as a 208. This picture is before I did the lift.

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I wonder what GM’s formula was for this. I’ve read 3/4 to 1-1/2” and I think the specs provided by Gear Vendors that @Blue Ox is looking up for me is even less (I believe I read 5/8” from another website re:gear vendors, but could be mistaken.

I appreciate the measurements. I’m interested in comparing the length of the driveshafts themselves. Might not be a good comparison, yours being the 205.

Which brings me to another question: how similar are the linkages and overall lengths between the 205 and 208? Besides the driveshaft since I’ll be getting a new one, are they a direct swap? I’d imagine the hole in the floor is the same.

 

[yevgenievich]

Measure the axle movement to the bump stop, then calculate the driveshaft movement and see how much it would move in the worst case for your vehicle.
Also have to verify how deep the yoke is on the splined area

 

[Frankenchevy]

Keep in mind that it rides in a bushing in the tail housing.

So this bushing and the rear most support bearing would take the brunt of the wear if there was an excessive runout condition at the yoke?

As long as the 1” creep to get it to change doesn’t get worse I’m not as concerned with that now. Mostly want to solve this vibration issue.

 

[Frankenchevy]

Measure the axle movement to the bump stop, then calculate the driveshaft movement and see how much it would move in the worst case for your vehicle.
Also have to verify how deep the yoke is on the splined area

Will do. I’m guessing 1-1/2” would be in the ballpark which is less than half of where I’m at now.

Iirc my yoke is a good 6” long, but I’m almost positive the splines go all the way in.

 

[Craig 85]

I appreciate the measurements. I’m interested in comparing the length of the driveshafts themselves. Might not be a good comparison, yours being the 205.

Which brings me to another question: how similar are the linkages and overall lengths between the 205 and 208? Besides the driveshaft since I’ll be getting a new one, are they a direct swap? I’d imagine the hole in the floor is the same.

Here's my floor with the 205. I can get some pictures from underneath if you need them. Let me know what your schedule is and I can bring my truck over for you to compare.

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[shiftpro]

It appears the general consensus here is, stick your shaft a little deeper into the hole..
lucky you.