The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 1971 Jimmy with 6.0 LQ4 / 4L65, 4" lift/33s.. basic family fun cruiser

Haggar · 09-07-2018, 01:50 PM

For the transfer case, I used an NP208 from an 80's K blazer. I used an advanced adapters 6 bolt 4L60e to 4 bolt output adapter, which included a 40 tooth tone wheel and VSS. This works with the factory output shaft, just bolts on, this all bolted to the NP208.

The transfer case mounts were the same as the NP208, so it all bolted to the factory crossmember, but it was moved forwards few inches.

I still don't have a front driveshaft installed, and I never installed the 4WD shifter.. just laziness on the shifter. I have the factory one with all the hardware from the same 80s blazer.. but I want to make it look more correct for 1971, it's a little plasticky.

Amazingly, the stock 80s rear driveshaft fit almost perfect, with just a conversion U-joint at the rear to mate with the 12 bolt.

My first test drive showed bad vibrations on deceleration.. this opened a whole can of worms. Turns out, a previous owner tossed in gears without any shims in the axle, and the pinion nut wasn't torqued.. it came loose on the test drive, and the pinion gear was eating into the carrier. Luckily I limped it home without issue.

Under the philosophy that anytime I take something apart, that's the best time to upgrade.. I swapped the Open 3.73s for 4.56 gears and an Auburn LSD. I struggled with the crush sleeve.. Wouldn't crush, then after pre-crushing in a press, it crushed too much.. trying to get the 2nd one right actually stripped the threads off the pinion nut! I ended up with a solid spacer and shims, and it dialed in perfectly. I used a Ratech pinion depth tool from Summit Racing, which helped out on the install. So everything was nice and nice, including all the wheel bearings, seals, correct preload and backlash.. Install it back into the truck, and then I can see that it's really close to binding, due to the shaft angle.

So, it was time for a CV shaft, which I got from Tom Woods, who I've had good luck with before. When I went to cut and rotate the spring pads, I found they were scab welded on and the welds were rusting through and cracked. So I'm glad that I found this. Looks like it came from a different vehicle and then someone welded the pads to fit the blazer, but I can't figure out why. Anyway, in the end, it all came together, and is working great now. The 4.56s make the 3200 stall converter happy, and the LSD is good and tight.

09-07-2018, 01:50 PM	#5
Haggar Registered User Join Date: Aug 2013 Location: Oxford, MI Posts: 38	Re: 1971 Jimmy with 6.0 LQ4 / 4L65, 4" lift/33s.. basic family fun cruiser For the transfer case, I used an NP208 from an 80's K blazer. I used an advanced adapters 6 bolt 4L60e to 4 bolt output adapter, which included a 40 tooth tone wheel and VSS. This works with the factory output shaft, just bolts on, this all bolted to the NP208. The transfer case mounts were the same as the NP208, so it all bolted to the factory crossmember, but it was moved forwards few inches. I still don't have a front driveshaft installed, and I never installed the 4WD shifter.. just laziness on the shifter. I have the factory one with all the hardware from the same 80s blazer.. but I want to make it look more correct for 1971, it's a little plasticky. Amazingly, the stock 80s rear driveshaft fit almost perfect, with just a conversion U-joint at the rear to mate with the 12 bolt. My first test drive showed bad vibrations on deceleration.. this opened a whole can of worms. Turns out, a previous owner tossed in gears without any shims in the axle, and the pinion nut wasn't torqued.. it came loose on the test drive, and the pinion gear was eating into the carrier. Luckily I limped it home without issue. Under the philosophy that anytime I take something apart, that's the best time to upgrade.. I swapped the Open 3.73s for 4.56 gears and an Auburn LSD. I struggled with the crush sleeve.. Wouldn't crush, then after pre-crushing in a press, it crushed too much.. trying to get the 2nd one right actually stripped the threads off the pinion nut! I ended up with a solid spacer and shims, and it dialed in perfectly. I used a Ratech pinion depth tool from Summit Racing, which helped out on the install. So everything was nice and nice, including all the wheel bearings, seals, correct preload and backlash.. Install it back into the truck, and then I can see that it's really close to binding, due to the shaft angle. So, it was time for a CV shaft, which I got from Tom Woods, who I've had good luck with before. When I went to cut and rotate the spring pads, I found they were scab welded on and the welds were rusting through and cracked. So I'm glad that I found this. Looks like it came from a different vehicle and then someone welded the pads to fit the blazer, but I can't figure out why. Anyway, in the end, it all came together, and is working great now. The 4.56s make the 3200 stall converter happy, and the LSD is good and tight.