84 GMC Diesel Jimmy Build

[bhays]

I bought my Jimmy in spring of 2005 after missing my suburban I sold when I moved from Washington State to California.

Picture of stock Jimmy going to Baja mexico (nov 2005) and a pic of my old sub:

Before I sold the sub, I removed the Dana 60 and the locker out of the 14 bolt for my future build....the Jimmy

 

[bhays]

After breaking the rear axle and running a 6.2 with over 300K, I decided before the next trip to mexico I would install the 1 ton running gear, rebuild the engine, and install a lift. As you read on, that is not how it turned out after 2 years of changing my plans...

 

[bhays]

A few month before I started tearing the Jimmy apart I purchased a Cummins 3.9L, which I was going to use for my 70 blazer that is still in a million piece. I start looking at using standard lift spring for the Jimmy; however, I ran into a few sets of 64" springs from my dad's dealership that came off of a late model 1/2 ton and 3/4. So proceeded to fab up my own rear shackle flip and forward mounts for the rear suspension and started modifying the frame up front to allow longer springs...

 

[bhays]

Some pics

 

[bhays]

Pics

 

[bhays]

You'll notice that I made my decision to pull the detroit and start fitting the Cummins (i.e. rubber engine isolater sitting on top of the frame). It took alot of measurements to get the engine in the right location because of the exhaust, oil pan, oil filter, and etc. Had to design and fab up a new cross memeber that would maximize axle clearance and avoid hitting the steering linkage. I rebuilt the turbo and alt on the motor for now. Since the cummins came with a TH475 (same as 400 but has K case and straight cut gars), I decided to romve the 700R4 and NP208. I had to tear apart the 475 to change out the output shaft. In order to do that you basically have to remove all the part out of the trans, so I decided to go through the trans and everything looked good and there was very little wear on the bands and clutches.

 

[bhays]

pics

 

[bhays]

I decided to used a doubler since I sold the 6.2 for $700 and traded a transmission for a 203 box. All o the factory cross members were not going to work; furthermore, they hung down 2" further than I wanted. I had to make a subframe that would connect the 203 and 205 together and used 92 Dodge cummins engine isolators to connect them to the new cross member. I also rebuilt the two transfercases using 32 spline outputs. By now I had missed the second trip to mexico and had to catch a ride...

 

[bhays]

more pics-sorry I dont have any good pics of the cross member. I will try today.

 

[skidog1us]

Very nice work...keep it coming!!!

 

[sledheadak]

nice work. whats the power going to be with the 4bt.are you going to add a intercooler?

 

[bhays]

The 4bt is rated at 120 hp and around 320 ft-lb of torque. It has about the same power as the 6.2 that I have had in the past, but I think I can get alot more reliable power out of it in the long run. I have a intercooler (siliconintakes.com) that I bought awhile ago. I have been saving money to upgrade the VE injection pump to a p7100; however, I have had no luck finding one for a 4 cylinder. They are a dime a dozen for the 6bt. I have been toying with the variable vane turbo idea, but I would have to design and program a microcontroller to operate it. I have seen a few mechanical VVT using a waste gate valve. I think my next project will be a cage; especially, since I have been going rough some rough terrain lately.

 

[K5 Jess]

 

[brian wafer]

nice work!

 

[Teck]

sweet!

 

[bhays]

Here are few pic of the front leaf suspension when I was done:

 

[bhays]

The leaf suspension would have flex extremely well: however, I did not like how the front bracket stuck out too far in the front. So I decided to tear it apart again and map out the frame (alot of measurements) and use a CAD design software called PROE and CATIA to design a four link suspension system. With PROE I was able to make a Kinimatic model of the suspension which allowed me to see how the suspension was going to move during different senerios.

 

[bhays]

It took several iteration on the design to complete. I made several card board templates before I had a shop lazer cut all the brackets (.250"). Here are a few pictures of the finished product. So far, I have been very happy with the performance. I works great on rocks, trails and highspeed (55 mph little Cummins needs more power and OD) desert stuff.

 

[bhays]

Next I built an engine cage and installed the FOA coilovers and installed FOA resevior shocks in the rear with a shock cage.

 

[Corey 78K5]

Holy sh!t!!