Author Topic: Best Practice?  (Read 2163 times)

Offline arby87

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Best Practice?
« on: August 10, 2017, 01:49:56 PM »
87 V10, 350/700R4, TBI, 4" Lift (springs up front, blocks in back), 33"x12"x15"


So my rear diff is leaking out both the front pinion seal and the rear cover (looks to have a crack in it- possibly thrown/broken gear) and needs a rebuild. Front diff is leaking out the cover, but came from the junk yard by the previous owner (still has junk yard writing on it).

I have no idea if he put the proper gear ratio front diff on. I have no idea of the current ratios in the back either. I figured I will have the diff shop look at both for a quote.

The main question I have is if I have to have them both rebuilt, and I am going to have to buy new pinion and ring gear for the rear, should I just go ahead and bite the bullet for a set of lower gears (4.11)?

Currently, as I make the truck more reliable, it is a home depot runner and taking stuff to the dump. I would like to maintain the ability to hit the mountain trails in the future, and possibly tow something like a pop-up camper on a mountain excursion- but that is years down the road. I am not sure I dare take this thing on the local highways (~70), but mainly because of steering and the lift- though it would be nice to take to work every now and again.

Just looking for opinions on best practices in this situation- guess I should also look into how expensive said gear sets may cost.....

Offline blazer74

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Best Practice?
« Reply #1 on: August 10, 2017, 11:00:00 PM »
4 inch lift is not that big of a deal.
Steering on these trucks has its inherent problems by design.

Worn parts and lack of steering correction like a raised steering arm for the lift can make for a puckering ride.
Bump steer is a bad thing.

With 33's and the 700r4 overdrive would be fine with 4:10 or 4:11 gears.

Considering you don't know  what you have now including rpm range in and out of overdrive how do you know you need different gears?
For example I run 35 tires with 4:10 gears with no overdrive puts me at approx 2200 rpm @ 55mph which is good for me. With overdrive I could run 4:56 gears to stay in my power band and prevent dropping in and out of overdrive at highway  speeds.

Obviously gears need to be matched front and rear.

Depends on condition regarding overhaul/rebuild of axles.
What is needed? Quite a bit of money to rebuild with all new bearings, seals, ring&pinion if required or just a reseal.
Not to mention traction devices.

All goes back to your use of the truck but foremost is a safe roadworthy vehicle.
« Last Edit: August 10, 2017, 11:05:13 PM by blazer74 »

Offline Irish_Alley

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Re: Best Practice?
« Reply #2 on: August 11, 2017, 07:23:38 AM »
depending on what you have laying around (tires and rims) and what condition yours are in now. think about getting a set of ĺ ton axles. you would have to change rims might be able to keep your 33s if you get a set of 15" 8 lugs and grind the calipers. more than likely the ĺ will have 4.10 ratio anyway just verify before you buy
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Offline arby87

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Re: Best Practice?
« Reply #3 on: August 14, 2017, 08:58:40 AM »
Well,

Dropped the truck off over the weekend with the local diff shop. Owner will take a look today to see the damage, but he is pretty excited about these old trucks. His recommendation is to pull the trigger on 4.56s due to the altitude (over 6000') and taller tires. Still pretty pricey just for the ball park figure of swapping just the gears- without knowing how much damage there might be in the rear as it stands now. But if the rear gears are shot and need replacing any way.....ungh.

Hard decision to make- I technically have the money, but was working on putting that into the house, and I have another kid on the way. But I also don't want to pay a bunch of money now to rebuilt the rear as it sits, then not have that gear ratio work out so well for my future plans with the truck (ability to go up in the mountains, possibly tow a small trailer).

The 3/4 ton axles- are those capable of a cross-over steering conversion? Or was that just a specific Dana axle model? 

Pretty soon I am going to have the money conversation with the wife- I think the truck is currently worth what I have in it, but the diff rebuilds is going to put me over that threshold. I wanted to go a little slower with some of these rebuilds, but so far everything I have put into has been necessary to either make it safe or to keep it going. Haven't even gotten to the engine tune-up yet, but I guess that's  the joy of picking up a cheap Craigslist truck.

Still love it though.

Parts truck possibility- just don't know where I would store it....

https://cosprings.craigslist.org/cto/d/1977-chevy-k10-14-bolt-axel/6233732159.html

Still would have the problem of wheel options with the new bolt pattern....
« Last Edit: August 14, 2017, 09:52:47 AM by arby87 »

Offline Irish_Alley

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Re: Best Practice?
« Reply #4 on: August 14, 2017, 10:38:57 AM »
With 33s I would not run 4.56 even with of it would kill the benefit of the od. With my 91v3500 it's setup was a thing 350 4l80e (of) and 4.10 with 33s. I could squeeze 12mpg out of the old crew cab. If I had 4.56 it would be lower


You don't need cross over, I think there is cross over steering avail for the Dana 44 and 10 bolt but imho you're waisting money. Last time I bought set of matching axles from the junkyard it cost me 200 (I think, it's been about 10 years ago). Came out with 4.10 ĺ ton axles. If you go with those you'll have to change rims. You can find 8 lug 15" rims but you have to grind the front caliper a little (Google " grinding 15" calipers" on mobile so it's a little difficult for me right now)
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Offline blazer74

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Re: Best Practice?
« Reply #5 on: August 14, 2017, 12:09:28 PM »


I used 32 tire size because that is closer to the true actual loaded tire size.

Agreed cross over is not needed.

Offline arby87

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Re: Best Practice?
« Reply #6 on: August 16, 2017, 09:29:17 AM »
So general consensus is a no on the cross over, and if needing gears, no lower than 4.11, and pick up heavy duty axles if the price is right and can swing the issue with the wheels (15" probably not going to work, not really looking to grind calipers).

Shop still has not gotten back to me yet- might need to call them today to see if they got a chance to crack open the diffs. Seems everyone in this town is extremely busy- took me two months to get a roofer to deal with a ventilation issue, three and a half to get an electrician for a panel upgrade, and who knows how long it will be for a general contractor for a sliding glass door issue or a plumber for my water heater issues. Also need to get a new furnace before winter hits, which seems to be early this year considering how cool this summer has been.

Guess it all depends on how messed up that rear diff is. I am thinking if there was enough damage to break a tooth and then send that fragment through the rear cover, who knows what else that fragment could have done or what might still be slinging around in there.

Will update if I hear back from the shop.

Here's hoping that for the sake of budget, my current axles/diff innards are good enough for the rebuild with the lower gear set. Finding heavy duty axles on the local junkyard search engine do not come back with favorable results- lots of people run a lot of off-road builds in the area, though mostly in the Jeeps, so supply is limited.

Offline arby87

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Re: Best Practice?
« Reply #7 on: August 17, 2017, 10:23:39 AM »
So, heard back from the shop- no Bueno.

- Rear diff (12 bolt) is completely shot- but that was to be expected.
- Rear driveline is messed up- about 2" too short as well.
- Front driveshaft barely hanging in there, about to fall out.
- Transfer case is shot, no additional details- something about the too short driveshaft causing an issue and being worn out.
- Front diff is pretty worn out, but carrier still good.
- 3.42 gears, front and back.
- Do NOT have a 700R4- has a T400.

So the shop gave me a new quote, is going to give me a few free parts he has laying around and wanted to clean up off his lot (which I am VERY thankful for), but for budget purposes and to get the truck at least serviceable for the upcoming winter we are looking at the following:
- Rebuild and re-gear the 12 bolt rear with 4.10s
- Rebuild and re-gear the 10 bolt front with 4.10s
- Source and modify a serviceable front drive shaft
- Source and modify a serviceable rear drive shaft
- Replace the pinion (yoke?) of the 12 bolt to a stronger unit
- Repair, as much as possible, the transfer case (np208)

Shop recommendation is this work will make the truck serviceable for now, but to start planning on a rebuild or replacement of the transfer case. He had another customer that might be willing to sell a freshly rebuilt np205, so he said he would look into that for me to see if I can make some sort of arrangement to pick that up for a future install. The 208 is probably fine for my applications (weekend warrior), but would recommend the 205 for peace of mind.

Thoughts?

On the value vs. worth argument, I will probably have about $7k into the truck after this- and it still needs some other smaller stuffs. Engine has a slight miss from time to time, but is probably fuel quality or spark related- otherwise seems pretty solid and runs strong. Transmission, other than the hard shifting into reverse (which is probably drivetrain related) hasn't given any other indications of problems other than a leaky pan. Yes, there is some wiring issues, but I feel pretty confident in figuring those out (I work with a lot of electronics and have some training) so I am not too worried about that right now- seems mostly limited to the towing brake booster wiring and the stereo tie-in on the headlight switch. Brakes are pretty decent- still feel strong enough and have good pads still- has a brand new booster and master cylinder.

I did just put a bunch of money into the front suspension (frame repair, frame bracing, ball joints, draglink) so that should be solid for awhile- and new tires.

Here's hoping for a solid 4X4 for the next couple years of enjoyment!

Offline Irish_Alley

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Re: Best Practice?
« Reply #8 on: August 17, 2017, 03:22:42 PM »
if youre going to put that much money into it you could get a donor half ton with a 700r4 if its the same bed length as yours you can reuse those driveshafts also. i know im kind of comparing apples to oranges with the owners but when i first got my 79 k20 i replaced the axles (from junkyard) and built a new driveshaft (longer) and rebuilt the CV joint in the driveshaft i would guess i had maybe 300. granted i have a lot of spare parts in arms reach between me and my buddy but for the front shaft we used one that was longer. i have a sm465 which is fairly small compared to the rest of the trans and i think i used a shaft from a th400 and cut it down and rebuilt that. i also had a 6" lift on mine so i needed a longer driveshaft. a 4" shouldnt need a longer than stock shaft and one in good shape will last you just have to take care of it.
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Offline arby87

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Re: Best Practice?
« Reply #9 on: August 17, 2017, 04:52:51 PM »
I did the ole Google search to see if it was a bad thing for having the TH400, and as with everything, there is pros and cons.

For my particular purposes, the TH400 is probably overkill and the 700R4 would probably have been better for the all-around purposes I want to use this truck for.

However, I did want to think about hauling something like a small camper down the road, so it appears the TH400 would be better for that application. But as to taking the truck to work (40 mile round trip, half in town, half ~70mph highway), the 700R4 would have been better for the OD. Not sure if there is going to be that huge of a difference in mpg in those conditions, and that was not the top concern (but among the top 5) for what I want this truck for.

Would love the idea of a parts truck - have no place for one. Checking Craigslist shows two in my area, but one already has the heavy duty axles- and nothing else but the body. The other appears to be mostly stock, but also is a manual and no motor. Both are around the $700 mark. 

Offline Irish_Alley

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Re: Best Practice?
« Reply #10 on: August 17, 2017, 05:11:46 PM »
the 700r4 can haul a trailer with no issues just keep it out of OD
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

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Offline arby87

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Re: Best Practice?
« Reply #11 on: September 07, 2017, 12:51:07 PM »
So, I finally have the truck back.

Really wish I had that parts truck, as once the rear diff parts came in and the shop dug into it, they found the diff casing and the axle shafts themselves were toast. Instead of a rebuild of the existing 12-bolt, I ended up paying for an entire rear axle assembly (shop did help me out on this a lot). The shop had recommended doing a custom build of a 10-bolt originally as that would have been stronger than the 12, but since we ordered all the parts for the 12 before we knew it was bad, we ended up keeping it. Oh well.

Any how, I have a practically new rear axle assembly, a rebuilt front diff, and new drive shafts with 4.10 gearing. The shop also reconfigured my speedo to show the correct speed now, which is nice.

Shop says my NP208 is a bit worn, recommends sourcing a NP241c to swap it out with down the road. Craigslist has a couple, usually around $200, which I guess is a good deal. Will have to see how much they are to rebuild.

At this point I am going to stop worrying about the drive train, and work more towards the mess my wiring harness is in right now- but that is for different thread I have already begun....