71 3/4 4x4 6.2 longhorn

[tazztoy]

I have a 71 longhorn box and frame that i'm turning into 4x4, and going to be running an '82 6.2 in it. questions are how hard is it to get a mid '90's five speed to bolt up to the 6.2? i've herd it's been done in other trucks. secound question, does any one know how/ what to do to bolt a nv4500 to a np205? i don't even know what they used for 4x4 duty in the newer trucks. question 3 what mods would i be "wise" to consider while the motor's on a hoist? i only want to put it in once!! i've seen a few others put 4x4 on a 2wd frame, what springs did you guys use? i'll be back to ask a few more questions, and gonna start a build thread once this thing kicks off when i get the parts to finish up the tractor in my shop.

[Tx Firefighter]

The 6.2 uses the normal GM bellhousing pattern, so the trans bolt up should be a non-issue. I can't answer your other questions though.

[special-K]

The 6.5s were bolted up to NV4500s,which were bolted to NP241s.The late bolt pattern (208s & 205s)is what the NV4500 bolts to.Just gotta watch spline length/count.

[Mister laugh]

Should bolt up no problem. There is a guy on the 73-87 side of things that has a 6.2 bolted up to an NV3500 and another one bolted up to an NV4500. Russell i think is his name maybe he can give you some pointers if you pm him. Both of his are 4x4 as well.

[thirdstreettito]

While you have the engine out you should do a few things to make it more indestructible.

The stud girdle kit. http://www.dieselservices.com/html/g...le_kit_p78.cfm

Dual idler gear valve. http://www.dieselservices.com/html/g...r_kit_p122.cfm

I would suggest that if the 6.2 has over 175K on it you should rebuild it. While rebuilding it do an overhaul kit. http://www.dieselservices.com/html/g...it_62l_p11.cfm

Also, for better performance install a Banks Ram-Air kit or Sidewinder Turbo kit.

Anymore questions I'll be glad to answer.

[tazztoy]

thank you guys, this is the kinda stuff i was woundering about.. what years would i find a late modle 205?? got one here off a 74 350auto can i convert it?


thanks third street your the secound one to metion the girdle the motor is at about 75000, runs starts real (started -10* when the glow pugs didn't work) good. was a camper haler for an older couple most it's life.

how does a guy find the cross members and motor/trans mounts, my frame was stripped when i got it. will a 1/2 ton's work?

any frount spring info any one??

thanx again.

[tazztoy]

I'm looking at these fgb52 hangers from diy4x4. has any one else run these? what lift do you get running the 52 inch springs? i have a new set off a 1/2 ton but woundering if i'd be better off getting some off a 3/4 for the extra weight i will have. also has anyone tried there frount crossmember? thanks JM

[Dooley]

Originally Posted by tazztoy

thank you guys, this is the kinda stuff i was woundering about.. what years would i find a late modle 205?? got one here off a 74 350auto can i convert it?

Factory transfer case on a 1974 V8 with automatic transmission was a 203.

[sierra4x4]

You might want to consider using a 73-87 4x4 frame becouse they are the same wheelbase as a 70-72 longhorn.

[Russell]

For the engine, I'd do everything as suggested above making sure to check for cracks in the mains while putting your girdle kit in. Make sure you replace the harmonic balancer as well, even if it looks alright, it is relatively cheap insurance. I installed a normal factory style balancer, but there is a fluid filled dampener on the market these days that is getting rave reviews from all sorts of diesel owners.

I personally decided to run a timing chain instead of the timing gear system. While I have yet to hear of any confirmed cases of a timing gear being the cause of an engine failure, I have heard rumors of it. Seeing as the timing chain is a once every 100 000 miles sort of a piece, I felt that the added expense and remote possibility of an engine failure were not worth it to me.

While my engine is turbocharged, and I do have my fuel turned up a bit, I would suggest that you install a pyrometer before attempting to increase your fuel to get more power from your engine. 1200F is the red line in my opinion, it doesn't take much more heat than that to start melting aluminum pistons.

Some power mods that can be done to help is to install free flowing exhaust (2.25" duals are plenty), a port matched J code military / HD (3/4 ton / 1 ton) intake, and a J code injection pump. The J code pump has slightly different timing curves than the C code, which helps with power a bit. Other than that, your only real option to increase power substantially is to turbocharge the engine. I am personally running a GM-3 turbocharger setup from a 93 6.5L diesel. The install was pretty straight forward, though my exhaust was a challenge and had to be run outside the frame rail. If you do decide to turbocharge your engine, limit your boost to approx 7 PSI, and watch your pryometer very closely. If you do turbocharge, I'd also recommend you run a set of 6.5L head gaskets (if you can, watch the alignment of your coolant ports in the head vs the gaskets!) with a set of ARP head studs. Keeping those heads down tight and the added thickness / strength of the 6.5L gaskets are even more relatively cheap insurance to keep that engine running strong.

Finally, make sure that you replace your main seals. Nothing is more annoying than getting an engine all nicely cleaned up / painted / installed then discovering that your front and rear mains leak -- Ask me how I know!

As far as bolting up a 5 speed goes, its fairly straight forward. I've installed an NV4500 in one truck, and an NV3500 in the other. For both transmissions I ran the factory hydraulic clutch components in both my trucks.

The truck with the NV4500 has a 93 transmission which has the early gear set and an external clutch slave. The factory 93 clutch fork and throwout bearing worked perfectly with the mid 80s diaphragm style pressure plate. Since you are installing your transmission into an older truck, I'll leave the details of how I installed the clutch master up to you to figure out for your generation of truck.

The truck with an NV3500 from an 04 bolted straight up as well. That truck I was unable to find a 6.2L flywheel for, and was forced to run a 6.5L single mass retrofit clutch system. The problem there was that the clutch stuff is unique to the 6.5L, and is quite a bit more expensive than the 6.2L / gasser combo clutch in the 80. The NV3500 has an internal slave cylinder / throwout bearing combo which once again worked nicely with the older 6.5L clutch components.

Both trucks I had to run a high hump floor pan, and cut my own custom holes in the floor for them. Both my trucks have an NP241 with uses a bulky shifter on the floor, and both interfered with the transmission shifters. The one truck I simply ran a very small shifter boot from a small car and left the t-case shifter as is, and the other I am working on a cable shifter system to relocate the shifter out of the shift stick's way so I can run a normal shifter boot.

Both transmissions of mine run a 32 spline short output shaft with a standard 6 bolt round t-case pattern built into the transmission tail housings. There are other NV3500s that run a 27 spline short output instead, so watch carefully.

Transfercase options that bolt directly on without any adapters for a passenger side drop truck include an NP208, NP241, and NP205.

The NP208 and NP241 are nearly identical t-cases visually speaking, except the NP241 can have either an electric speedometer, or cable drive, and all have a better low range ratio than the NP208. Both the NP241 and NP208 come in both 27 and 32 spline inputs, and either one will bolt directly to either transmission without any adapters.

The NP205 comes in either a 10 spline or 32 spline input, but beware that you get a short input 205. 205s usually come with a mechanically speedometer drive, but can be had with an electric speedometer setup as well. 32 spline NP205s can be found behind TH400s, and SM465s from the early 80s through to the very early 90s (I believe 91 was the last year for the 205), and so long as you get a 32 spline short input with a 6 bolt round pattern, it'll bolt straight on without any adapters.

Keep in mind that both the NP208 and NP241 are exceptionally tough transfer cases. The NP241 is rated for over 700 ft lbs of torque, possibly even more than the 205 is rated for, and is less than half the weight which is definitely a consideration when bolting one to an aluminum tail housing. The only weakness with a 208 or 241 is the aluminum housing, but if you protect it well with a skid plate, you shouldn't have any trouble with one.

As far as the suspension stuff goes, I've never run a truck of your generation, so I can't help much there. I do know that 63" springs are awesome out back on my truck, just make sure you install some anti-wrap devices to keep spring wrap down to a minimum.

If you have any other diesel / 5 speed questions, please don't hesitate to send me a PM, or post up here. I am not on this forum nearly as much as I used to be, but I'll try and check this topic frequently.

[Dooley]

Originally Posted by sierra4x4

You might want to consider using a 73-87 4x4 frame becouse they are the same wheelbase as a 70-72 longhorn.

The 1973 -1988 2 dr regular cab C/K and R/V long bed pickups
do not have the same wheelbase as a Longhorn.