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1994 GMC Yukon 2-Door SLE 6.5TD Updates

PAToyota

Hill-William
Joined
May 27, 2020
Member Number
1545
Messages
341
Loc
South Central Pennsylvania, USA
I picked up my Yukon a few years ago. It was in relatively decent shape, but heading towards thirty years old it needed some refreshing.

I tore things apart to work on updating the interior of my Yukon - recovering the headliner, putting in sound mat, new carpet, and other upgrades.

To start, I found a pair of GMT-800 bucket seats for a good price and made up brackets out of TS2x4x1/8 to mount them. The brackets mount to the original bolt holes in the floor pan with holes in the tops of the brackets to reach the bolts. Then the seat rails bolt to the tops of the brackets. It took several iterations of putting the seats in, marking things, pulling them out, drilling the holes, and so forth to get everything lined up but it all worked out perfectly. I started by placing the console to get those holes in the right place. Then the inner seat rails mount to those same bolts, so that enabled me to locate the holes on the outer rails. Sitting the seats right on the floor pan put them much lower than the original seats (the GMT-800 must have higher corrugations in the floor pan), so the 2" of the tube steel put them at the perfect height.

I like a firmer seat with some side support, so the GMT-800 seats are much better than the original bench (or the GMT-400 buckets).

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PAToyota

Hill-William
Joined
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Member Number
1545
Messages
341
Loc
South Central Pennsylvania, USA
Next project was doing battle with removing the riveted GM half-ton balljoints. I did the top ones first and they weren't too bad - I just had to grind the heads off and then pop the remainder out with an air hammer.

But the bottom ones were a serious pain. Grind the heads off, drill them out (drill, drill, hit with air hammer, drill, drill, sharpen drill bit, drill, drill, etc) far enough that the air hammer was pushing them through instead of just mushrooming them inside the balljoint flange, and then pop them out with the air hammer.

Replacing the balljoints and bushings was a difference of $122 for balljoints and $53 for Energy Suspension bushings ($175) versus $110 for upper and $360 for lower complete arms ($470). For the complete arms, I could get Moog for upper, but lower options were limited (Driveworks?). So, for my work, I saved about $300 and have a better feeling about the components I installed.

Oh, and the local shop wanted $1200 to do the work - again, with questions about the actual components used...

Balljoints Collage.jpg
 

PAToyota

Hill-William
Joined
May 27, 2020
Member Number
1545
Messages
341
Loc
South Central Pennsylvania, USA
One of the issues that plagues the 6.5L GM diesels is the battery setup. There is a battery on either side in the front corners of the engine bay, connected across the top of the radiator, ground sides both connected to the engine, and positive sides connected to the alternator on one side and the starter on the other. The OEM cables are undersized and not well made (leading to corrosion), both of which limit function and cause battery drain. Attending to this issue has been on my list for awhile for both the Yukon and the K2500, but I finally got around to ordering up supplies to make it happen.

You can see the corrosion on the cable here:

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This one was further butchered by the PO, just making matters worse.

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So we're going to take the time to make some good cables for the old girl.

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PAToyota

Hill-William
Joined
May 27, 2020
Member Number
1545
Messages
341
Loc
South Central Pennsylvania, USA
Backing up a bit, I should give some more of the history since buying the truck...

I happened to see the truck on craigslist with very few details. So I went and looked at it and found it to be a 1994 6.5TD Yukon (2-door). Over the years I had seen a few of them - they’re appealing little suckers. So far, they had either sold before I could get to them or were in worse shape than I wanted to deal with. I was first in line on this one and it looked to be in semi-reasonable shape.

Upsides: Body looked nice - somewhat rare for any vehicle over ten years up here in the salt belt. Engine sounded good, idled and ran evenly. Ride didn’t indicate any obvious issues. It had an SSDiesel Supply FSD Heat-SyncTM kit and 4” turbo back exhaust. I don’t think it had any other performance improvements - the woman I talked to wasn’t quite sure about chips or such.

Downsides: Had over 200K on it. Tires were bare. A/C didn’t work. Interior rear hatch release didn’t work - still have to open it with the key from the exterior. Crossover pipe was not leaking, but judging from the rust it was living on borrowed time. Biggest downside was that it had been used on a farm, so the interior was in sorry shape - dirty and some interior trim busted or gone. Bare minimum would be a weekend spent with a steam cleaner and long term plans were for a new carpet and seat covers. Considering all of that, I was really surprised at how good the exterior was.

So to get it to pass State inspection (it was still registered in a neighboring State) I was looking at a bare minimum of crossover pipe, new set of tires, miscellaneous parts and (for my own benefit) a full interior cleanup. So it ended up being about $1500 for tires and parts to pass the inspection.

The woman selling it wanted almost $4K for it. KBB was showing under $3K for Excellent Condition and closer to $2K for Good or Fair Condition. However, KBB just looks at some formula and doesn't take into account that these are rare and/or could be desirable, so I was willing to go a bit higher than the KBB estimate.

The seller said she was selling it due to the price of diesel (about $3.00 to $3.40 a gallon around here at the time). Otherwise, she really liked the vehicle and hated to part with it (ironically, I talked to her a few months afterwards and she had to sink a pile of money into the "new to her" vehicle she replaced the Yukon with). From her comments, it sounded like the other interested parties are younger guys looking to “roll coal” with it. Due to the rarity, I had a feeling that she’d get her price even with the bald tires and trashed interior if I passed on it or tried to talk her down too low.

The only thing that was causing me to hesitate was the interior. But I’d rather have good mechanicals and a body that doesn’t look like a rusty old can. I ended up talking her down a bit to where I felt comfortable and she didn’t feel like she was giving it away. Other than the interior and the tires, it was in pretty great shape.

Here it is from sitting in my driveway after taking it for a test drive while we were negotiating.

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PAToyota

Hill-William
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1545
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South Central Pennsylvania, USA
Life gets in the way of things and it took me a few months to clear out the time to spend on the Yukon to get it through inspection so that I could get it on the road. I did start stockpiling parts to get ready to work on it. It needed the stabilizer bar links and going over things, the rest of the steering needed attention. While I was in there I fiugured I might as well do the front suspension as well to ride pretty nicely by the time I’m through. At the time the gear drives for the 6.5TD had ceased production and were becoming scarce, so I added one of those to the pile. Also picked up a serpentine belt and tensioner for both it and the K2500. And I found a set of wheels and tires on craigslist.

I finally found a long weekend to dive into things. Swapped the tires, replaced the sway bar end links, replaced a burnt out headlight bulb, and went over a number of other things to get it in for the State inspection so that I could get it on the road to see if there were any other issues I should be aware of.

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PAToyota

Hill-William
Joined
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Member Number
1545
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341
Loc
South Central Pennsylvania, USA
That got it through the inspection, but also turned up weeping oil cooler lines. It looked like the PO had taken some time to wash things off so this wasn’t apparent when I bought it. So I picked up a set of Lubrication Specialist, LLC Oil Lines and Cooler - which was something I added to the K2500 as well.

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With the inspection and mechanicals straightened out, I mostly just drove it while planning on the next steps.

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PAToyota

Hill-William
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1545
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Loc
South Central Pennsylvania, USA
I did clean all the upholstery, strip out the carpet, pull the headliner and trim, and install sound insulation.

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I picked up the replacement fabric to recover the headliner too.

And that brings me up to date to doing the seat swap.
 

PAToyota

Hill-William
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Member Number
1545
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Loc
South Central Pennsylvania, USA
I'm doing up a set of the same seats for my K2500, so I pulled the brackets out to take measurements and duplicate them.

While they were out I cleaned them all up, powdercoated them, and installed 1/2"-13 rivnuts rather than needing nuts to install the seat tracks to the brackets. I used a die grinder to mark each one (PO = Passenger Outside, etc) and the Front of each bracket.

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arse_sidewards

Masshole
Joined
May 19, 2020
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71
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Loc
Worcester County
If I had to find an example of the worst choice of fastener ever plillips screw in rivnut in plastic would be near the top of the list. You're lucky you didn't split the plastic installing it. We'll see if the riv-nut spins or if you can even put enough torque on the phillips to do that when you go to remove it.

The GMT900 buckets are definitly a big step up from damn near any 90s truck seat.
 

wvracer821

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do your self a favor and relocate that PMD to the front. thats a major down fall of those 6.5s even with the heat sink you added
 

PAToyota

Hill-William
Joined
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1545
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Loc
South Central Pennsylvania, USA
If I had to find an example of the worst choice of fastener ever plillips screw in rivnut in plastic would be near the top of the list. You're lucky you didn't split the plastic installing it. We'll see if the riv-nut spins or if you can even put enough torque on the phillips to do that when you go to remove it.

The GMT900 buckets are definitly a big step up from damn near any 90s truck seat.

You lost me. Philips screws? Split the plastic? Those are steel rivnuts in a piece of 2x4x1/8" steel tube to hold the 1/2" dia. bolts from the seat tracks. The steel tubes bolt through the floor to the existing holes for the previous seats.

[edit] Realized you meant the fan shroud and battery cable. The shroud is pretty thick there and was no problem for the rivnuts. The fasteners are stainless steel truss head machine screws. No problem to remove them.

do your self a favor and relocate that PMD to the front. thats a major down fall of those 6.5s even with the heat sink you added

Yeah, that's from the previous owner. It hasn't given me issues, but I have the longer harness and is getting remounted.
 

arse_sidewards

Masshole
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[edit] Realized you meant the fan shroud and battery cable. The shroud is pretty thick there and was no problem for the rivnuts. The fasteners are stainless steel truss head machine screws. No problem to remove them.
I think you got lucky on the shroud. We'll see what happens when it's time to remove them. I hope you used anti-sieze.
 

PAToyota

Hill-William
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Honestly, I don't see the issue. The plastic is pliable, so there isn't much chance of it cracking. The fasteners are just holding the cable in place, there isn't any real stress on them. And the truss heads give a cleaner fit than if I used hex heads. They're still just standard 1/4"-20 threads, so I've never had issues removing them.

Ironically, I was adding a side box to my tool box the other day and when I removed the handle from the tool box, it was held on by rivnuts and truss head machine screws from the factory...

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wvracer821

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I love the build though. I'm partial to these old GMs as I have a 95 CCLB K3500 with a 6.5 and 5 speed in it that was given to my dad by a family friend. he drove it for years after we fixed it up and now I have it. I plan to give it some love in the next couple years and hopefully keep it from rusting to pieces
 

PAToyota

Hill-William
Joined
May 27, 2020
Member Number
1545
Messages
341
Loc
South Central Pennsylvania, USA
When I did the battery cable upgrade, I still had life in the batteries in the truck so I temporarily terminated the ends to work with the stock side post terminals.

I've never been a fan of the side posts, though. Messing around with the screw-in connections - particularly if you have any additional ring terminals added - is a real hassle and I just don't feel you get the same connection as a top post.

Earlier this year I picked up a pair of Group 34/78 800CCA Dual Terminal Batteries for the Yukon. Until I had a moment to reconfigure the cables, I could continue to use the side posts. Also, once converted, I could still use the side posts for additional connections and also to add in a NOCO on-board battery charger.

The diesel setup with the two batteries has always been hard on them. The alternator charges the driver's side battery, but the starter pulls from the passenger side battery. In a perfect world, that shouldn't be an issue if all the electrons flow as they should. In practice, it always seems to kill the passenger side battery first. The heavier duty battery cables should help and I also make a point to swap the batteries side to side (similar to rotating tires) to get more even wear. Still - particularly if the the Yukon ends up sitting for awhile - the batteries need to be topped off every now and then. I have a battery charger, but it can be a hassle to connect things up and also charging it out in the weather if I can't get it into the garage is another issue. So an onboard charger that I can just plug an extension cord into makes it an easier task.

I had some time to work on things this past weekend, so I set to work...

The NOCO charger is very nicely packaged - if you're into such things.

I've got a TEMCo Hydraulic Cable Lug Crimper that will do from 10ga to 600MCM. It does a very nice job and also comes with plus sized dies for thicker lugs. It even imprints the size into the lug while crimping to confirm that you used the correct size die (the plus sizes don't have this feature). It's overkill for 10ga, but I've done lugs for building wiring as well - service entrances and such.

I'm using Fastronix top post terminals. They're nice without spending a ton of money.

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DieselTahoe

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Aug 6, 2020
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2541
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Couple of things I did on my 95 2 door Tahoe with the 6.5 was put a 96+ air box, water pump, and dual thermostat crossover, ran consistently 10-15 degrees lower coolant temperature. Not sure if the crossover pipe is available aftermarket but I was able to pull one off a 97ish parts truck. Also upgraded to the Stanadyne gray PMD with a heat sync behind the front bumper.

Always cool to see another one of these around, looking forward to seeing progress
 
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wvracer821

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I listened to a podcast this morning about a guy building a 500+ hp 6.5 and he mentioned this company a few times. I thought of this thread and figured I would post a link for other 6.5 people. I know that it can be a struggle finding aftermarket upgrades for these things.

 

Cheepin

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Did you change the front bumper? The diesels have the ones with 2 holes in them for cooling.
 

PAToyota

Hill-William
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1545
Messages
341
Loc
South Central Pennsylvania, USA
I wasn't the original owner of either my K2500 or the Yukon and both came to me with the "standard" bumper. I have my suspicions that the original bumpers were damaged on each and "standard" bumpers were more plentiful at the pick-n-pull.
 

350TacoZilla

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MD
Very cool truck that you don't really see many of. I'm surprised you didn't have any type of cooling issues with the standard bumper on the 2500, I had a suburban 2500 6.5 and bunch of guys on the forums back then started having issues with wrong bumper or anything that covered the holes like fog lights.
 
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