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73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Topic started by: xgruntusmc on January 02, 2014, 09:45:41 pm

Title: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 02, 2014, 09:45:41 pm
hey everyone, new guy here with a quick question.  I've got a '78 K10 4WD I bought a couple months back.  I haven't really gotten to use it that much but the two times now that I've put it in 4WD it works fine but the shifter will launch out of gear when I'm using it.  It's not making any noises (that I've been able to hear anyway), manual hubs and it'll go into 4WD without a problem, staying is the issue.   I believe stock it has 3.07 gears in it and i'm thinking that it's probably a gear issue and those need to be changed out (which i'm going to up to 3.73's) but i just wanted some other opinions on this matter.  also it's got the stock 350 four bolt main that i was going to strip, hot tank, bore 40, hone and build up, thoughts on this? i look forward to talking with y'all, take it easy
-Gib
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Engineer on January 02, 2014, 10:15:54 pm
What tranny, and transfer case?
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 02, 2014, 11:30:45 pm
transfer case
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Irish_Alley on January 02, 2014, 11:36:05 pm
first make sure its not hitting the sheet metal. sometimes they can seat into 4wd but the sheet metal will prevent them from locking in (best scenario)
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 02, 2014, 11:40:01 pm
just so i'm clear here, the sheet metal on the floor in the cab?
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Irish_Alley on January 02, 2014, 11:43:53 pm
yes. it could be a bad mount causing the t-case to sag a little, then if you get on it it can move a little more and hit the sheet metal. or if someone made a 2wd cab into a 4wd and didnt cut the hole big enough. you can also try to adjust the linkage. if theses ideals dont work you might have to rebuild the t-case. what case do you have?
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 02, 2014, 11:50:00 pm
i'm not positive what TC i have to be honest with you, i haven't gotten into it that much.  and it'll shoot out going slow not even getting on it.  it wasn't modified from a 2WD it has always been 4WD
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Irish_Alley on January 02, 2014, 11:54:42 pm
203 shift pattern
4Low lock
4Low
N
4High
4High lock

205 shift

4Low
N
2High
4High
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 03, 2014, 06:33:06 am
thanks for that information, with that being said i have the 205
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: dvdswan on January 03, 2014, 11:19:28 am
hopefully its the trans mount.   but does it only do it in 4HI or does it do it in 4LO as well?
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 03, 2014, 12:34:06 pm
haven't even tried it in 4 low yet, but it does it without fail in 4 Hi i know that much.  like i said originally, i'm planning on changing out the gears to 3.73 anyway, but I was trying to find out if someone knew if there was another issue i should be expecting
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: dvdswan on January 03, 2014, 12:44:01 pm
crawl under and see if the trans mount is bad, you my need to grab a prybar and see if it moves.  then check the cab, you can tell by unscrewing the boot cover and shifting in 4HI and see if it hits.
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 03, 2014, 01:12:01 pm
dave thanks, i'll check it out today or tomorrow when i get a chance. also, sweet little truck you just got, i was looking for exactly that, but all the ones i found were in horrible shape, but i'll get some pics of my 78 K10 up shortly on here and PB for you to check out. i want that bucket seat set up you have though!!! lol
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 03, 2014, 04:23:50 pm
here's the link, let me know if it works             http://s982.photobucket.com/user/Adam_Gilbeau/story/34521
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: dvdswan on January 03, 2014, 05:32:04 pm
clean looking K10.  I like the rally wheels. 

(http://tivohd982.photobucket.com/albums/ae308/Adam_Gilbeau/IMAG0183_zps271fd958.jpg)
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Engineer on January 03, 2014, 05:32:42 pm
Here is what I would check.

There are two hex shaped plugs on top of the NP205. These retain the shift rail poppet balls, and springs. Take them both out to compare to see if either is weak or broken.

If this checks out grab the output yokes and shake them. They shouldn't have any play. If they do you have a bearing out. You may not see any play and still have a bearing out.

BTW, what is this "xgruntusmc" business? I thought once a Marine, always a Marine.....
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: momorales511 on January 03, 2014, 06:57:19 pm
Probably a fork inside the case.....there is little plastic tips on the "fingers" of the forks(there's a high and a low) that wear out. Its a pretty easy fix and parts are cheap.
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 03, 2014, 07:57:59 pm
Thanks, my plan with this is to yank the engine, hot tank, bore 30-40 over, hone it and build it up from there.  Once that is done i'll give it a 6" suspension lift, 3" body and slide 37" IROC SS tires on it.  then through out i'll be picking away at cosmetic issues to pretty things up a little.  the interior needs some TLC, especially the door cosmetics.  it's currently got the stock 350 4BM, it's got a 12 bolt rear with 3.07's but i'm planning on changing the gears to 3.73 before too long.  I'd love to change the bench to a set of buckets but we'll see if that ever comes to pass.  I got lucky though as there isn't a bit of rust on the dang thing to be concerned about as the only rust i've been able to find isn't even big enough to put a pinkie in and that's on the bottom of the rocker.  it's got a new alternator, fuel pump, intake, carb, valve covers, and headers.  since i've been in the military since 2000 i really haven't had an older vehicle that i could work on and that's what drove me to this and i'm slowly picking away at things on it.... Mo and Engineer, thanks for the advice as well, engineer, i'm assuming the bearings you're talking about are the hub bearings correct? (that was actually my next job i was going to take on after i get back from a little bit of business) and "xgruntusmc" is basically implying that i was a grunt in the Marines, i'll always be a Marine, i'm just not a grunt anymore, but thanks and yes you're right, once means always :)
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Engineer on January 03, 2014, 08:10:34 pm
The bearings I am worried about are the ones in your transfer case.

If your transfer case is jumping out of gear it almost always means an excessive amount of play somewhere. A loose bearing will cause the shaft it is intended to stabilize to walk.

The NP205 will put up with a ton of abuse. But it does have it's limits.
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Greybeard on January 24, 2014, 03:04:22 am
Thanks, my plan with this is to yank the engine, hot tank, bore 30-40 over, hone it and build it up from there.  Once that is done i'll give it a 6" suspension lift, 3" body and slide 37" IROC SS tires on it.  then through out i'll be picking away at cosmetic issues to pretty things up a little.  the interior needs some TLC, especially the door cosmetics.  it's currently got the stock 350 4BM, it's got a 12 bolt rear with 3.07's but i'm planning on changing the gears to 3.73 before too long.  I'd love to change the bench to a set of buckets but we'll see if that ever comes to pass.  I got lucky though as there isn't a bit of rust on the dang thing to be concerned about as the only rust i've been able to find isn't even big enough to put a pinkie in and that's on the bottom of the rocker.  it's got a new alternator, fuel pump, intake, carb, valve covers, and headers.  since i've been in the military since 2000 i really haven't had an older vehicle that i could work on and that's what drove me to this and i'm slowly picking away at things on it.... Mo and Engineer, thanks for the advice as well, engineer, i'm assuming the bearings you're talking about are the hub bearings correct? (that was actually my next job i was going to take on after i get back from a little bit of business) and "xgruntusmc" is basically implying that i was a grunt in the Marines, i'll always be a Marine, i'm just not a grunt anymore, but thanks and yes you're right, once means always :)

Nobody addressed this the issue of you wanting to redo your engine. While it's yours to do with as you please my suggestion is to leave the bores as small as is necessary to clean them up. Just saying that you want to go 0.030 or 0.040 over is pointless until you know it's necessary. It won't gain you any horsepower if that's what you are after. And it reduces the overall life of the block. They can only be opened up so much and then it gets expensive.

So, another suggestion is to let a respected speed shop or mechanic do all the decisions making on the machine work and you just guide the decisions on what parts to add to it to make it all work together. There is a ton of horsepower to be gotten out of a 350 with the right application of select parts. Not simply the parts that sound cool. With certain flow characteristics of the engine there would be certain improvements to the induction side as well the exhaust side. A four wheel drive used primarily on the street will work much better with more low end torque as I'm sure you already know. So putting a 6 inch tall open plenum intake on 1.88 heads will cause nothing but grief as will using a really large mechanical secondary carb that opens at 2000 rpm on a relatively stock engine. If you like intimate contact with your steering wheel have at it. Having 14/1 compression and trying to use pump gas, using angle plug heads and stock exhaust. These things don't necessarily work well together. I've seen it being done, I've never seen it being done successfully.   
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: xgruntusmc on January 25, 2014, 12:54:36 pm
hey boss, i appreciate the info.  i haven't really toyed around with cars or trucks in about 14 years when i was in HS..lol.. i guess i was always ignorant, but i was under the impression boring out an engine and putting the bigger pistons in there would give you some more power by giving you a bigger engine displacement is that wrong? and as far as everything else goes, i was going to go pretty standard if you will, except for the oversized cam and a set of 200 or 210 heads.  a friend/mechanic of mine who builds race cars and trucks said to expect around 400HP at the crank by doing this.  what's your intake on this? i'm always up for suggestions/opinions because i don't know everything and i like to take other opinions into consideration when talking with others about it. 
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Greybeard on January 25, 2014, 09:09:18 pm
I certainly don't know everything about an engine but by increasing the size about 5 cubic inches you aren't going to add more than a minibikes worth of power to it. Maybe a couple of pounds of torque nothing to write home about. My 350 is 355ci right now, it didn't make much difference, but add in a nice off-road cam, a good dual plane manifold and a good (read near new) carb and you will have a nice street truck that won't need a diet of regular fuel. Others have alternate and just as effective ways to modify it also. The need for speed needs to be tempered by the fact that it is a 4-wheel drive truck. Guaranteed if that engine gets near 400hp you will start breaking the stock drive train. BTDT. On my old 78 I needed to upgrade to a 14 bolt, a 4.5" drive shaft to handle the extra large u-joints I fitted, beefed up tranny mount, etc. It cascades into throwing money at it. That's no problem if you are up to it. Just sayin. It can be opening a can of worms. The difference is my truck was still popular back in the eighties when I owned before. Parts are much older now and getting a little harder to find. I've been looking around the webz and see there is a bit more aftermarket support these days but except for the custom built stuff I have to wonder about the quality. Aftermarket fenders have cost around $100 for the last 15 years. A good new fender at the time was well over $300 on a good day. Makes me wonder... 
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Irish_Alley on January 25, 2014, 10:48:19 pm
grey some not all, but some of the price drop is because of people staying competitive now. yes you will lose some quality in cheaper ways to make the parts but its not just one or a couple companys making the parts anymore. but i think you (usmc) will find more power if you stroke the engine and make it a 383. or if you have a 3k budget you can by a engine and be making over 400 hp and tq
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: Greybeard on January 27, 2014, 12:08:43 pm
I agree Irish, with everything you said. I've been out of it for a while so I'm not really well versed on the newer stuff.

I found out the hard way (like I usually find stuff out) that I could have bought a better engineered engine from GM than I made with $3500 dollar investment in sourcing all the parts from my engine.

I think stroking the engine is a good idea on the one hand. On the other hand, I am finding it harder and harder to advocate taking old original iron and making life ending permanent changes to it. Maybe because I'm old. I know they make new cast iron blocks but they don't make new old numbered cast iron blocks.

My block is a 010 side stamped block with a 4-bolt main set. That, I am told, is to signify a high nickle content, hi-po specified block. No big deal maybe, but to me it means a strong block that can handle some HP abuse. Not that I'm going to ever do that but it's capable if I ever change my mind. The is ample cast available down under to assure that it never breaks. Maybe it's inconsequential, maybe not. IDK, what I do know is that if was made in the early years it will never be made again. It might be copied and even improved, but never again will it be made original.  ;)
Title: Re: 78 K10 shooting out of 4WD when driving
Post by: roundhouse on April 28, 2014, 07:38:22 am
If you want to run 37 tires you're going to be at a minimum replacing the axle gears.  And possibly the entire axle.     If you have. 10 bolt rear axle it will self destruct fairly quickly with a new high HP engine and 37 inch tires

You're go ing to need 3/4 ton axles to run 37s