Np208 Refurb Advice

[Frankenchevy]

Third time’s a charm! Hopefully

Big bearing means it’s better, right? Lol

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[Frankenchevy]

When diagrams refer to an oil pump gear and oil pump housing, is the gear just and impeller and the housing a shroud to direct the oil being pumped by the “gear”?

as far as I see, the gear doesn’t turn anything. It’s driven by the shaft, but in turn doesn’t drive another gear inside the housing. The housing is just a piece of plastic with a seal...

am I missing something?

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[Blue Ox]

Nope. That's what it is.

Basically an Archemedies screw as an oil pump.

 

[Frankenchevy]

Transfer case back together, new TC installed...again, all buttoned up but about a quart shy of ATF for the TC. Heading into town to Walmart to get another gallon of Valvoline max-life. Only $18 a gallon there, which is good when you've been through 3-4 gallons in the past week and a half.

I'm excited to see how a TC with some stall will feel. The last one was tight for towing. I think is was more geared towards diesels. definitely didn't allow it to slip at all of the line. it was supposed to drop tranny temps and freeway speed by 200rpm. I'm mostly backroads up to 60mph when I drive the truck, so this should be a vast improvement and be good until I 4l80 swap at some point this year.

 

[SquareRoot]

Frankenchevy-

I've been following your threads chasing that vibration. I have a similar issue. Have you gotten it back together and driven it yet?

 

[Frankenchevy]

Frankenchevy-

I've been following your threads chasing that vibration. I have a similar issue. Have you gotten it back together and driven it yet?

Yes. With every thing I do it gets smaller and smaller, yet it’s still there a little. That makes me believe the source is in something I haven’t yet touched in the drive train. It was just playing off 35 year old tolerances magnifying the sound and the tightening of those tolerances by replacing with new is slowly muting them.

I’m not sure now if my next step will be the rear end or transfer case rebuild. The rear end can be done by the shop same day, while costing $1400—including the cost of a $700 truetrac, etc. While the transfer case would likely take me a weekend and about $200 in parts. The last piece of course being the th400 at around a grand.

$2500 away worst case scenario, lol

I’ll be perturbed if it turns out to be wheel/tire balance all along. I’ve had it checked a few times already.

 

[SquareRoot]

Do you have a build thread on this vehicle? I think I saw in different posts some of the kids you've done. I think our trucks are very similar?

Mine: 85 K20

Cucv axles, 14ff-dana60-4:56 locker.

Th400, 208 t-case.

I just had my trans rebuilt incl opening the convertor to braze fins and balance unit.

 

[Frankenchevy]

Do you have a build thread on this vehicle? I think I saw in different posts some of the kids you've done. I think our trucks are very similar?

Mine: 85 K20

Cucv axles, 14ff-dana60-4:56 locker.

Th400, 208 t-case.

I just had my trans rebuilt incl opening the convertor to braze fins and balance unit.

Yeah there’s a hyperlink below my post. Although, none of the vibration related stuff is in there. I need to catch it up.

 

[Craig 85]

I’ll be perturbed if it turns out to be wheel/tire balance all along. I’ve had it checked a few times already.

Sorry, smart ass response to follow...

Have you checked to see if the tires are round? I know this is not as big of an issue due to tire technology and the size you're running, but back in the day when my friends were running bias ply tires (Ground Hawgs and Grand Prixs) you could technically balance the tire, but still have it out of round.

 

[Frankenchevy]

Sorry, smart ass response to follow...

Have you checked to see if the tires are round? I know this is not as big of an issue due to tire technology and the size you're running, but back in the day when my friends were running bias ply tires (Ground Hawgs and Grand Prixs) you could technically balance the tire, but still have it out of round.

I’m not even sure how I’d go about checking that myself. Maybe roll them across my slab and watch the center bore?

Two easier things I’m going to try:

I’m going to replace the polyurethane mounts for the trans with rubber ones and I’m going to try suspending my exhaust in a way that allows more flexibility/movement.

 

[Craig 85]

I’m not even sure how I’d go about checking that myself. Maybe roll them across my slab and watch the center bore?

For the rears, put the rear on jack stands on a solid surface. Put the truck in gear and let it idle. Mount something horizontal to the tire and see if the gap changes as it rotates. Move the fronts to the rear and do the same thing.

A tire shop may be able to do this on the balance machine, but I'm not sure with the safety hood.

 

[Frankenchevy]

pulled the headers and unbolted the exhaust when I got home today. Hopefully I'll find a set of header gaskets that fit my header ports (1.5"x1.75" oval). I'd like to find a pair of Remflex 2021's if possible. I'm hoping to rehang the exhaust tomorrow with a little more 'give' as well as install the rubber trans mounts I picked up on the way home today to replace the new urethane ones in there now.

Why the heck do header manufacturers build their headers for vortec era trucks with oval ports when the head has the rounded square. I've read that you want the small drop out of the bottom of the head's exhaust port, but why not may a rounded rectangle so the top corners match better?

 

[Frankenchevy]

Which rebuild kits have high quality parts for the np208?

I was looking at something like this:

https://www.summitracing.com/parts/spz-77915/

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and this:
https://www.summitracing.com/parts/clo-10-014/

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Not sure if anyone’s stuff is 100% American made...