1990 GMC 1500 Jimmy

[Justin V]

@campfire isn't talking about the lug nuts, he is talking about the number of bolts that hold the diff cover on

 

[scpaul]

I understand that he's talking about the cover bolts. I was wondering if the # of lugs would give him any info. about the axle and maybe how many splines the axles have, or if I might be better off getting some aftermarket axles. I'm just trying to get all the info that I can. The last thing that I want to do is get it broke down/stuck in our swamp.
In that area all of the fields and yards have ditchs about 6' deep and 10' wide to allow the high water table a place to drain to. We can go 3 months without rain and still have a little water flowing in those ditchs. Our deer, hogs and turkeys almost never go thirsty or hungry. On the Nat'l news, they showed the damage to the p-nut and corn crops; alot of those pics were taken within 5 to 10 miles of our property, only that was the high ground. Those giantg hogs that you see on tv are mostly from the Savannah River basin. It's about 25 or so miles as the crow flies. I've been put in a tree 3 times. Now I have a 3" Mag. Taurus Judge and a S&W 460 Magnum. I usually keep one or the other on me most of the time.

Thanks again, Paul (sorry about the misunderstanding re: the cover bolts)

 

[Justin V]

No worries. We are only looking for number of cover bolts because there were enough variances over the years that counting lugnuts isn't enough info...

 

[campfire]

I understand that he's talking about the cover bolts. I was wondering if the # of lugs would give him any info. about the axle and maybe how many splines the axles have, or if I might be better off getting some aftermarket axles. I'm just trying to get all the info that I can. The last thing that I want to do is get it broke down/stuck in our swamp.
In that area all of the fields and yards have ditchs about 6' deep and 10' wide to allow the high water table a place to drain to. We can go 3 months without rain and still have a little water flowing in those ditchs. Our deer, hogs and turkeys almost never go thirsty or hungry. On the Nat'l news, they showed the damage to the p-nut and corn crops; alot of those pics were taken within 5 to 10 miles of our property, only that was the high ground. Those giantg hogs that you see on tv are mostly from the Savannah River basin. It's about 25 or so miles as the crow flies. I've been put in a tree 3 times. Now I have a 3" Mag. Taurus Judge and a S&W 460 Magnum. I usually keep one or the other on me most of the time.

Thanks again, Paul (sorry about the misunderstanding re: the cover bolts)

Ok, quick primer on GM axles after about 1980. 8.5" 10-bolt axles were only used on 1/2-ton rigs and all have 6-lug hubs. They were never offered with any form of heavy duty truck or even a 1/2-ton with towing package. They're the bottom of the line for full-size axles. If you beat on your truck or get into aggressive rock crawling, it's not terribly hard to break one of these. Or, if you have a G80 axle, the axle may randomly fail someday even if you baby it. These axles continued to be produced until...this year?

9.5" 14-bolt semi-float axles were used on 3/4-ton and later "heavy half" trucks, and can come with 8-lug or 6-lug hubs. These axles show up all over the place, lots of applications.

10.5" 14-bolt full float axles were used in 1-ton trucks after the 9.5" axle came out. Previous to this they were used in both the 1-ton and 3/4-ton trucks. They all have 8-lug hubs.

Both 1/2-ton and 3/4-ton used front 10-bolts (6-lug and 8-lug respectively), 1-ton trucks used Dana 60 front axles.

Prior to about 1980 GM used Dana 44 fronts and 12-bolt rears in place of the 10-bolts, and the 10.5" full floater on the 3/4-ton rigs. Axle changes phased in gradually over a few years as GM used up its older inventory.


Getting back to this thread, your K5 would have come with 10-bolts front and rear. There were no 3/4-ton K5s, they are all in 1/2-ton configuration.

My 14-bolt comment was referring to the 1995 truck. In that series some 1/2-ton trucks came with 9.5" 14BSF axles, while baseline models came with 8.5" 10-bolts. But square 1/2-tons all came with 10-bolt axles (much to the chagrin of many rock crawlers).

 

[campfire]

As for your truck, the G80 is a liability if you're looking for back country dependability. But assuming you aren't beating on the truck, the 10-bolt should be fine for general swamp driving. If you work the truck hard or are prone to opening up the throttle a bunch, you may want to think about installing a heavier axle. GM never intended the 10-bolt to be used for big tires or towing duties. But it sounds like in your usage it will be fine.

If you want to upgrade to a 14BSF axle, the only axles that come set up for your squarebody will have 8 lugs. The 6-lug option didn't come out until the next series. You can either convert to 8 lugs, install 6-lug shafts into a squarebody axle, or get a newer axle and move the spring and shock mounts. There are no wrong answers here, but again, this is only if you think you want extra axle strength.

 

[scpaul]

Campfire, I know that I must not be understanding you. Did you say that the 8.5" rear end was never offered on any heavy duty or even 1/2 ton tow pkgs?

The tag in my glove box shows GU6 followed by G80. The window sticker shows on the right side ; "Options Installed By Manufacturer", in the lower part of the right side it has Locking "Differential-Rear Axle", then 6 lines down it has: "Rear Axle 3.42 Ratio". Am I confuzzled or according to the window and glove box stickers say that I've got an axle on a H.D.Tow Pkg. that shouldn't have been put in this truck?

I know that I've got to be missing something but, I've read your post several times and that's what I keep coming up with. What am I missing? If I have to, I'll lay some cardboard on the briars and try to crawl under it. I don't remember the ends being serviced so all the tags/markings should still be on it. If I do get under it, are there any other things that I should look at ?

Paul

 

[max 02]

Campfire, I know that I must not be understanding you. Did you say that the 8.5" rear end was never offered on any heavy duty or even 1/2 ton tow pkgs?

The tag in my glove box shows GU6 followed by G80. The window sticker shows on the right side ; "Options Installed By Manufacturer", in the lower part of the right side it has Locking "Differential-Rear Axle", then 6 lines down it has: "Rear Axle 3.42 Ratio". Am I confuzzled or according to the window and glove box stickers say that I've got an axle on a H.D.Tow Pkg. that shouldn't have been put in this truck?

I know that I've got to be missing something but, I've read your post several times and that's what I keep coming up with. What am I missing? If I have to, I'll lay some cardboard on the briars and try to crawl under it. I don't remember the ends being serviced so all the tags/markings should still be on it. If I do get under it, are there any other things that I should look at ?

Paul

Campy is saying that the 8.5 ten bolt is the only axle GM ever offered in any of its half ton Truck, Suburban`s or Blazers regardless of weather it had a tow package of not from 1981 and up.

The earlier years had 12 bolt rear ends
But they are not any stronger than the 10 bolt.

 

[campfire]

Yes, 1/2-ton square bodied trucks came with 10 bolt rears. Period. Every square K5 is in this category. Prior to this they all came with 12-bolt rears, as Dean said.

Once the GMT-400 (round-nose) series started (1988 for pickups, 1992 for SUVs), 1/2-ton trucks could also come with the 9.5" 14BSF. Since that point, trucks with towing packages or "heavy half" models have consistently come with the heavier axle. So your 1995 truck could have either one.

The only confusion on your K5 is whether it has 28-spline axle shafts or a 30-spline axle shafts. There was a switching point that came around 1990, but I don't remember exactly when the split is. Do some research, the answer is out there. This is only relevant if you decide you want to replace the carrier in your existing axle. Whatever carrier you get must match your axle shafts, or they won't fit.

 

[campfire]

Here is a sample diagram showing GM axle options. The truck axles are on the right hand side. The 4 truck axles all have unique shapes, and bolt counting makes it pretty easy.

Much easier than identifying Dana axles (which seem to all come with very similar cover shapes and matching bolt patterns ).

 

[scpaul]

Excellent, I guess that I'll be going under it today. I want to know and I'd also like to get a general idea of what I'm looking at total money wise.

Due to the fact that the tires, even as old as they are, aren't showing any signs of dry rot and I parked it with the front end so that the sun never really got on them very much, none have ever gone flat or low, I'm going to try to use them, at least to begin with, so I think that it has an OBD1 port. Can't the ECM be reprogrammed to allow for tire size? I also never got an answer about the TBI being able to be used with slightly larger injectors or does the computer control that so that it can be reprogrammed. The TBI is the same one used on larger stronger engines engines, isn't it?

I do remember looking for a Dana 60 for my hot rod. It was a pain and I almost never found one that would work and it still had to be narrowed.

Thanks again for the rear end guide, I will be looking, Paul

 

[campfire]

Excellent, I guess that I'll be going under it today. I want to know and I'd also like to get a general idea of what I'm looking at total money wise.

Due to the fact that the tires, even as old as they are, aren't showing any signs of dry rot and I parked it with the front end so that the sun never really got on them very much, none have ever gone flat or low, I'm going to try to use them, at least to begin with, so I think that it has an OBD1 port. Can't the ECM be reprogrammed to allow for tire size? I also never got an answer about the TBI being able to be used with slightly larger injectors or does the computer control that so that it can be reprogrammed. The TBI is the same one used on larger stronger engines engines, isn't it?

I do remember looking for a Dana 60 for my hot rod. It was a pain and I almost never found one that would work and it still had to be narrowed.

Thanks again for the rear end guide, I will be looking, Paul

Engine tuning doesn't care about the tire size, it's the transmission shifting points that are affected. And the 700R4 is a mechanically-controlled transmission, no ECM involvement. Yes, you can do a lot with an ECM tune, but you won't be able to benefit from more fuel unless you also increase the air input (otherwise you're just going rich). I don't see any reason to touch the ECM unless required by engine mods.

 

[scpaul]

I looked at them, the front is the 10 bolt that has a slightly oval cover and the rear is the GM 8.5 that looks like the cover was shaped to clear the ring gear and has a small notch or deviation on the right side of the cover. It's not very large, just not a smooth curve on that side.

So, It looks like there's a rear end repair in my future. Does anyone make a replacement carrier that's stronger where I can keep it as stock as possible that has a good track record?

Paul

 

[campfire]

I looked at them, the front is the 10 bolt that has a slightly oval cover and the rear is the GM 8.5 that looks like the cover was shaped to clear the ring gear and has a small notch or deviation on the right side of the cover. It's not very large, just not a smooth curve on that side.

So, It looks like there's a rear end repair in my future. Does anyone make a replacement carrier that's stronger where I can keep it as stock as possible that has a good track record?

Paul

10 bolt = 8.5" axle, the housings and internals are the same (though front and rear obviously are different once you get outside the pumpkin).

They should have looked very similar. The notch on the right side sometimes has a fill plug in it, sometimes not.

Front:

Rear:

There are replacement carriers, both locking carriers and beefed up open carriers. But the stock open carrier has a fine track record, I wouldn't worry about it unless you abuse the rig. The more relevant question might be whether you like having a locker in the rear and whether you want to replace the gov-lock with another locker.

 

[scpaul]

The rear one looks right but the front one looked more oval, like the second from the right on top. Is that the same one as you sent the pic of and I'm seeing it from a different angle? I really want to keep the locking/limited slip axles. I don't want a 2 wheel drive, one in the front and one in the rear.

I just went back and looked at the I.D. chart you sent. The fr. cover doesn't have the place where it looks like it was relieved for the ring gear and I don't remember any drain plug on the front cover.

 

[disenough]

I don't get down there to often, maybe just for a Craig's list run. I can let you know if I'm heading that way.
I'll pm you my #.

 

[campfire]

The rear one looks right but the front one looked more oval, like the second from the right on top. Is that the same one as you sent the pic of and I'm seeing it from a different angle? I really want to keep the locking/limited slip axles. I don't want a 2 wheel drive, one in the front and one in the rear.

I just went back and looked at the I.D. chart you sent. The fr. cover doesn't have the place where it looks like it was relieved for the ring gear and I don't remember any drain plug on the front cover.

Not all of them have the drain plug. But it should be 10 bolts in an oval pattern, that is what GM used on trucks like yours. They didn't offer any other options.

You have a number of traction-aid options ranging from being locked all the time to a clutch-slipping posi unit (and everything in between). Prices vary.

GM didn't offer the gov-lock in the front, but you can add an aid of your choice up there if you wish.

 

[scpaul]

Disenough, I'll do the same. When you call, be sure and remind me of this conversation, the quicker the better. It seems that I've wound on every phone list that there is. I try to be nice but, my nice doesn't last long.

Ethan, I guess that I'll just have to cross that bridge when I come to it. Did you say that the front axle could have parts added and lock the front end, or are you just welding it? You said something about a limited slip unit for the front axle? A limited slip front end I can imagine but, a locked steering axle sure wouldn't be the best for downtown driving and probably pretty rough on front tires. But, there is a way to leave the stock housings in it and put guts in them that won't break unless I get "Stupider" than normal. If I were to stick it in certain places that I go, it could be in 4 ft. or more water in a couple of days. Then I'd have to walk out. I've had my right hip replaced and will probably will have to do the left in the next few. At least when I'm driving my 1500 P/U, I've got my 4 wheeler and trailer to get myself and my stuff out.

Thanks y'all, Paul Can you tell that it wouldn't be the first time? My hunting buddies call the ATV my "Redneck Wheelchair". I guess that it is. It's my third, I've had 2 stolen before this one. The 5 ft. of chain that I bought to secure it cost me $65 w/a discount. It's hardened grade 8 and weighs around 40 lbs.

 

[campfire]

Ethan, I guess that I'll just have to cross that bridge when I come to it. Did you say that the front axle could have parts added and lock the front end, or are you just welding it? You said something about a limited slip unit for the front axle? A limited slip front end I can imagine but, a locked steering axle sure wouldn't be the best for downtown driving and probably pretty rough on front tires. But, there is a way to leave the stock housings in it and put guts in them that won't break unless I get "Stupider" than normal. If I were to stick it in certain places that I go, it could be in 4 ft. or more water in a couple of days. Then I'd have to walk out. I've had my right hip replaced and will probably will have to do the left in the next few. At least when I'm driving my 1500 P/U, I've got my 4 wheeler and trailer to get myself and my stuff out.

Inside the pumpkin, the carriers are the same for both the front and rear axles. So both axles have the same options for traction aids. Yes, a locked front end is not the brightest idea for your use, but a clutch-based posi unit would be a benefit. For my truck I have an Eaton Posi unit to go in my front axle (although I have not gotten it installed yet).

Like I said, you can modify as much or as little as you want, there's nothing wrong with just leaving it open.

 

[ZooMad75]

I'm going to take a different outlook with a different set of suggestions for this K5. Bear with me...

The truck has been mothballed for a long time. Memory can be foggy. CRS was mentioned in the opening post. So, rather than throw the baby out with the bathwater to bring the truck back on line, why don't you get the truck running first? Change all the fluids, pack the front bearings. Engine oil/filter, Air filter, fuel filter. Change the plugs, wires, cap and rotor. Get it running. Yeah, it might have felt sluggish 10 years ago or more, but part of it could have been needing a tune up or a fuel filter. Keep this in mind, TBI small blocks are some of the most bulletproof engines GM ever made. No they weren't crazy high HP, but maintained well they can go for well past 200,000 miles with no major issues. If the engine isn't smoking like mad at any time or under acceleration I'd run it. Staying with the engine, you don't NEED headers. Work on getting it rolling, once it's back to roadworthy you can start to think about modifying. TBI systems won't net a huge gain with headers for power or fuel economy without some external tuning. I'd leave it be and get it running.

While you have pulled the diff covers on both ends you can inspect the inner workings. I agree with what Campy has told you about the Gov-lock in your rear axle. However, if yours has been in your family since it was new (which is pretty rare by the way) you know the history. You know if it's been beat on or babied. Yes they can give up the ghost at any moment. But with the cover off, you'll find if you have any metallic chunks, debris or flakes in the oil. You can make some decisions at that time to run it or throw it out. Given your inexperience you'll be paying to have somebody to install the open carrier. That's probably going to run you a chunk of your budget.

Just getting the truck "freshened up" is going to add up to a few bucks in fluids, filters and tune up parts. It needs to be done so that you don't have a neglected maintenance item bite you in the keester when you least expect it. Get it to the point where you can start driving it again. Once driving, you'll find other things you want to fix or modify to make better. If you start the modification process prior to getting back on the road with it, you might get stuck in the "Might As Well" process that has been coined here. That's the time where you start fixing one issue, see another issue and fix it and see another, then another, then another. Meanwhile the truck hasn't left the garage or driveway in months or years. It can blow the budget in a big way. Not saying it's bad, but if you want to drive the truck you shouldn't blow it all the way apart if the budget of time and money won't allow it. Once you can get it running, the spark of being able to drive it ignites the internal drive to move forward to make it better. Keep projects to what you can get done in a weekend. Drive in, drive out. It limits the confusion of CRS when you took it apart a week ago and can't remember what bolt goes where. Get to know it. Run it, have fun with it.

 

[scpaul]

Damm, Don't ya' just hate a smart aleck; especially when he's right. You do have some real good points. Now let me AX some questions. It has the duel line(1 return) fuel sys. With that system can I gravity feed the fuel pump, assuming that it has a pump on the block (never noticed) and not just in the tank. Looking at the spec/option sheet a couple nights ago it listed 2 possible gas tanks. 1 was about 20-25 gal. and it said that the other was 34?. This one holds 38 without packing it. Did they allow that much error in the specs. I also seem to remember parking it with 1/2 to 3/4 tank of gas. Does this "Gas Refresher" work enough to try it (seriously doubt it) with that much gas, or I had thought about siphoning/pumping as much out as possible so it won't clog the tank p/u if it's not gone already.

I was going to try to make a list to start it up, but I think that I'll let y'all make suggestions. I do think that I should pressurize the oil system after I change the oil but I hate to pull the distributor. I've got to start somewhere. Which/what type of oil would you use, since it's going to be removed so soon. I do think that I'll use a pretty good filter. I'm a strong believer in Sea-Foam, I've seen it do some things that I wouldn't have believed if I hadn't seen it. Use a gravity feed fuel system after I get as much gas out as I can. It does have a fuel pump on the engine doesn't it?

Campy mentioned "Pumpkin", the ctr. sect. can't be pulled as an assy from the other side, can it?

List of things to do before I try to crank it: