Larry
Bigassgas Explorer
Looks like it’s been a long time since I’ve posted anything on the K10. It seems the Polar Bear Burb does most of the web-wheeling as the K10 is pretty much a completed project outside of maintenance.
Anyway, for the last month I’ve been busy licking wounds and making improvements to the rig from last year’s trips, even though last year the truck only saw one trip to the Mohave Rd & Death Valley in March and the OX13 trip in May. Once the stork dropped off our baby girl in July the bigassgas8.1L has pretty much just been sitting in the garage :elkgrin:.
The first order of business was to rework the fuel transfer system. As we all know these old GM trucks were available with two side saddle fuel tanks and a dual tank switch valve. The problem is the dual tank switch valve doesn’t work with the 8.1L as the 8.1L has a large 3/8 return line whereas the switch valve only has a 5/16 return port. This is not a problem for those swapping in smaller LS Gen III small blocks as those have a 5/16 return line on the years a return line was actually used. On this truck when the large return line is plumbed through the little 5/16 port it drives the fuel pressure well above 100 psi as it is too restrictive so I chose to use the passengers tank as a storage tank with a center mounted pull type fuel pump to transfer fuel from the RH to the LH tank which houses the in-tank fuel pump to feed the engine. I was actually using a 6.5L diesel lift pump for this chore but the problem was that pump allows fuel to pass even when the pump is not running so basically fuel was transferring by itself as pressure built up inside the tank. That got annoying so I replaced the RH tank with a new 1987 EFI tank with the same in-tank fuel pump I use on the LH side. The fuel is plumbed through a hose that connects to the LH tank fuel fill vent which is the same procedure the aftermarket tanks such as Transferflow, etc use. So far this seems to be working really well. Fast too! I'm anxious to see how it works in the real world once we hit the road again.
The next order of business was to deal with the 5th gear noise that started on the way home from Death Valley last March. I figured she would need the typical 5th gear and mainshaft that these NV4500s are so famous for and I didn’t want to use the same Advance Adapters kit that I used back in 2010 when I first installed this transmission because I didn’t want to cut a brand new mainshaft. So, I found a nice 1985 round pattern 205 through a friend of a friend for a decent deal and rebuilt it and changed the input gear to the short 32 spline so no adapters would be needed to mate it to the NV4500. While it was apart I also did the shift rail upgrade that allows for use of front wheel drive only. I got her all back together last night but didn’t have a chance to go for a test drive yet as the batteries were dead (poor truck hasn’t left the house since last June)....maybe tomorrow I'll be able to take it for a spin.
Here is the story in pictures:
A round pattern 205 as I received it in May 2013
I didn’t get around to ripping into the round 205 until December 2013. It came to me with a slip yoke rear but I used the rear section from another 205 I had laying around with a 1350 fixed yoke. I also did some trading with ORD for the long 32 spline input for a short 32 spline input. This picture is just after I gutted it in preparation for sand blasting. The internals were in great shape, almost like new. I only had to replace two bearings in the whole thing.
The rear transfercase section actually came out of the 205 that was in my dad’s ’78 K20 wrecker. No wonder the speedo hasn’t worked in that truck for many years! Look at that speedo cog! The good news is you can still buy new ones from GM.
I also got a new speedo adapter for it as well. There is a seal inside the adapter that isn’t replaceable but you can get new adapters from GM also. The new adapter is not pictured here though.
With getting away from the AA kit also meant I had to find an OEM rear trans cover and modify it to clear the shift rail and idler nut.
My ain’t that purdy! Red primer is the period correct OEM color of the NP205.
I used a wood spade to make the hole. Hey, it worked!
After making an access hole for the range shifter rail and idler shaft nut clearance
The stock GM NV4500 trans cover needs to be clearance to allow the 4 NP205 front seal retainer bolts to pass through. This was before I made the mod
It doesn’t take much elbow grease with a rattail file to make a pass through for the tcase front seal retainer bolts. A bit of flat filing on the seal retainer itself was also required as it appeared to be too thick to seat into the transmission cover properly.
Here tis right before I stabbed it in the truck.
This is what $475 worth of driveshaft’s look like. Stupid expensive! Errr! The rear needed a new stub and slip yoke to accommodate the change to the larger 1350 u-joint at the tcase. I’ve had a 1350 at the rear axle for quite a while but the tcase end was really small, like a 1210 or something. The front shaft needed the works…CV rebuild, new joints, the stub and yoke were loose so they got replaced and it needed to be lengthened almost 2”. This is not the same shaft that came out of the truck as I changed from the u-joint type flange to a flat flange. All the U-joints are the Super Brute solid core cross shafts.
Beefy. It’s an optical illusion where the ebrake cable looks like it is near the yoke when it is actually a few inches away from it.
I spent a lot more time this go around fine tuning the ORD twin stick adjustment. I really like the way it shifts now. Having front wheel drive seems really weird to shift only that stick. BTW….to run only in front wheel drive the rear shifter must be left in neutral, which is nice so you don’t end up running the front and rear in two different range speeds.
The trans coolers are HUGE! The coolers also add 2 quarts of capacity. Either they are going to help keep the fluid cooler or help keep it really hot from the heat of the exhaust :lol: Time will tell! The picture also makes it look like the front shaft is uncomfortably close to the trans cooler but there is plenty of room. The Dana 60 will have to crash through the 8.1L oil pan before the shaft hits the cooler.
This is the old NP205 with the Advance Adapters pieces. Everything in this picture is for sale. If interested PM me. The nice thing about this kit is the fact you can use a 2wd or 4wd NV4500.
Now that all this is done I’ve still got a ton of work to do to it before the next big desert trip coming up in May following OX14. The rear winch needs work (again) because it stopped working (again). This damn Milemarker winch is broke more than it actually works. The old as dirt - very light duty Hickey Sidewinder winch on the front always works. It’s never failed me once!
Then I need to get it up to Denver to spend a week with Phoenix as they are going to remodel the kitchen area to the latest and greatest stove/sink combo. I am ready for something different than the rattley old Suburban brand stove found in many RV’s that is in it now. It is also getting fitted with 100W solar power.
Lastly, I may still have an issue with the rear axle to figure out. Last spring on the Death Valley trip it puked out over a quart of 80W-90. When I got home I changed the rear cover to a larger capacity cover then filled it with Synthetic thinking it just overheated. A couple months later I drove it to Arizona for the Overland Expo and the sumbish puked out another quart of oil out the vent on that trip. Talk about a friggen mess all over the rear of the truck, camper, Trasharoo, fuel cans, water can, etc. when it decides to have its gear oil orgasm. I’ve since replaced the vent hose and installed a new vent so the trip to Denver should be a good test for that. I just don’t know what would cause this thing to start puking out oil of the vent just out of the blue. Never had a problem until the DV trip. There is zero noise coming from the axle that would point towards any bearing issues either. A real head scratcher
That’s the update on the Bigassgas8.1L K10 for now :ylsmoke:
Anyway, for the last month I’ve been busy licking wounds and making improvements to the rig from last year’s trips, even though last year the truck only saw one trip to the Mohave Rd & Death Valley in March and the OX13 trip in May. Once the stork dropped off our baby girl in July the bigassgas8.1L has pretty much just been sitting in the garage :elkgrin:.
The first order of business was to rework the fuel transfer system. As we all know these old GM trucks were available with two side saddle fuel tanks and a dual tank switch valve. The problem is the dual tank switch valve doesn’t work with the 8.1L as the 8.1L has a large 3/8 return line whereas the switch valve only has a 5/16 return port. This is not a problem for those swapping in smaller LS Gen III small blocks as those have a 5/16 return line on the years a return line was actually used. On this truck when the large return line is plumbed through the little 5/16 port it drives the fuel pressure well above 100 psi as it is too restrictive so I chose to use the passengers tank as a storage tank with a center mounted pull type fuel pump to transfer fuel from the RH to the LH tank which houses the in-tank fuel pump to feed the engine. I was actually using a 6.5L diesel lift pump for this chore but the problem was that pump allows fuel to pass even when the pump is not running so basically fuel was transferring by itself as pressure built up inside the tank. That got annoying so I replaced the RH tank with a new 1987 EFI tank with the same in-tank fuel pump I use on the LH side. The fuel is plumbed through a hose that connects to the LH tank fuel fill vent which is the same procedure the aftermarket tanks such as Transferflow, etc use. So far this seems to be working really well. Fast too! I'm anxious to see how it works in the real world once we hit the road again.
The next order of business was to deal with the 5th gear noise that started on the way home from Death Valley last March. I figured she would need the typical 5th gear and mainshaft that these NV4500s are so famous for and I didn’t want to use the same Advance Adapters kit that I used back in 2010 when I first installed this transmission because I didn’t want to cut a brand new mainshaft. So, I found a nice 1985 round pattern 205 through a friend of a friend for a decent deal and rebuilt it and changed the input gear to the short 32 spline so no adapters would be needed to mate it to the NV4500. While it was apart I also did the shift rail upgrade that allows for use of front wheel drive only. I got her all back together last night but didn’t have a chance to go for a test drive yet as the batteries were dead (poor truck hasn’t left the house since last June)....maybe tomorrow I'll be able to take it for a spin.
Here is the story in pictures:
A round pattern 205 as I received it in May 2013
I didn’t get around to ripping into the round 205 until December 2013. It came to me with a slip yoke rear but I used the rear section from another 205 I had laying around with a 1350 fixed yoke. I also did some trading with ORD for the long 32 spline input for a short 32 spline input. This picture is just after I gutted it in preparation for sand blasting. The internals were in great shape, almost like new. I only had to replace two bearings in the whole thing.
The rear transfercase section actually came out of the 205 that was in my dad’s ’78 K20 wrecker. No wonder the speedo hasn’t worked in that truck for many years! Look at that speedo cog! The good news is you can still buy new ones from GM.
I also got a new speedo adapter for it as well. There is a seal inside the adapter that isn’t replaceable but you can get new adapters from GM also. The new adapter is not pictured here though.
With getting away from the AA kit also meant I had to find an OEM rear trans cover and modify it to clear the shift rail and idler nut.
My ain’t that purdy! Red primer is the period correct OEM color of the NP205.
I used a wood spade to make the hole. Hey, it worked!
After making an access hole for the range shifter rail and idler shaft nut clearance
The stock GM NV4500 trans cover needs to be clearance to allow the 4 NP205 front seal retainer bolts to pass through. This was before I made the mod
It doesn’t take much elbow grease with a rattail file to make a pass through for the tcase front seal retainer bolts. A bit of flat filing on the seal retainer itself was also required as it appeared to be too thick to seat into the transmission cover properly.
Here tis right before I stabbed it in the truck.
This is what $475 worth of driveshaft’s look like. Stupid expensive! Errr! The rear needed a new stub and slip yoke to accommodate the change to the larger 1350 u-joint at the tcase. I’ve had a 1350 at the rear axle for quite a while but the tcase end was really small, like a 1210 or something. The front shaft needed the works…CV rebuild, new joints, the stub and yoke were loose so they got replaced and it needed to be lengthened almost 2”. This is not the same shaft that came out of the truck as I changed from the u-joint type flange to a flat flange. All the U-joints are the Super Brute solid core cross shafts.
Beefy. It’s an optical illusion where the ebrake cable looks like it is near the yoke when it is actually a few inches away from it.
I spent a lot more time this go around fine tuning the ORD twin stick adjustment. I really like the way it shifts now. Having front wheel drive seems really weird to shift only that stick. BTW….to run only in front wheel drive the rear shifter must be left in neutral, which is nice so you don’t end up running the front and rear in two different range speeds.
The trans coolers are HUGE! The coolers also add 2 quarts of capacity. Either they are going to help keep the fluid cooler or help keep it really hot from the heat of the exhaust :lol: Time will tell! The picture also makes it look like the front shaft is uncomfortably close to the trans cooler but there is plenty of room. The Dana 60 will have to crash through the 8.1L oil pan before the shaft hits the cooler.
This is the old NP205 with the Advance Adapters pieces. Everything in this picture is for sale. If interested PM me. The nice thing about this kit is the fact you can use a 2wd or 4wd NV4500.
Now that all this is done I’ve still got a ton of work to do to it before the next big desert trip coming up in May following OX14. The rear winch needs work (again) because it stopped working (again). This damn Milemarker winch is broke more than it actually works. The old as dirt - very light duty Hickey Sidewinder winch on the front always works. It’s never failed me once!
Then I need to get it up to Denver to spend a week with Phoenix as they are going to remodel the kitchen area to the latest and greatest stove/sink combo. I am ready for something different than the rattley old Suburban brand stove found in many RV’s that is in it now. It is also getting fitted with 100W solar power.
Lastly, I may still have an issue with the rear axle to figure out. Last spring on the Death Valley trip it puked out over a quart of 80W-90. When I got home I changed the rear cover to a larger capacity cover then filled it with Synthetic thinking it just overheated. A couple months later I drove it to Arizona for the Overland Expo and the sumbish puked out another quart of oil out the vent on that trip. Talk about a friggen mess all over the rear of the truck, camper, Trasharoo, fuel cans, water can, etc. when it decides to have its gear oil orgasm. I’ve since replaced the vent hose and installed a new vent so the trip to Denver should be a good test for that. I just don’t know what would cause this thing to start puking out oil of the vent just out of the blue. Never had a problem until the DV trip. There is zero noise coming from the axle that would point towards any bearing issues either. A real head scratcher
That’s the update on the Bigassgas8.1L K10 for now :ylsmoke:
Don't get me wrong, Suburbans are nice and all... but this thing is in a league of its own!
