Okay I have a donor truck for my conversion

[PJensen]

Well it looks like those members that were pulling for the conversion won that tug o war, LOL!



I have a 91 1/2 CTD, getrag, 4x4 for a donor truck.



I have heard many stories on the getrag blowing up what is the best way to fix this?



What parts are required to bolt a NP4500 or a NP5600 ?(6 speed) to my 91 1/2 CTD?



What parts etc are required to bolt the Diesel NP205 to the NP4500 or NP5600?



What operations do you recommend for a 150K mile B5. 9 before I plant it in them frame rails?



Thanks for the info and Ill be hitting the archives too.

 

[Sled Puller]

Check for parts and suggestions at www.enterpriseengine.com.

They are down by Columbus, Ohio, and swap parts all the time.



Gene

 

[Joseph Donnelly]

Std Trans in Texas (800-std-tran) has very good stuff at the right price and can give you advice on your transfer case, etc.



As far as the engine, I suggest a good valve job; port the head too if you will go over about 350 hp. Other stuff can be added later, like a torque plate and injectors.



Pull the block plate and check the rear cam plug and oil galley plug for leaks; also the rear main seal. Retain the dowel pin under the gear housing cover, and put in a new front seal. Note that the seals are teflon coated and you install them with the crank DRY. Put Loctite between the seal and its housing/cover.

 

[PJensen]

A First Gen Cummins can go to 350HP? WOW!



I didnt know that. What is the ball park on the Torque with a HP output of 350?



Will the rest of the drivetrain hold that kind of power? Ill have to talk to the trans people about that Getrag and a new clutch too.



Is there a good Cummins shop in the Illinois area that does valve jobs and cylinder head porting?



I will need to get a factory manual on this 91 1/2 as well for a good reference on repair work.



Here is another question I have. My crew cab has Dana 60's front and rear with 4:10's and Lock Rite's in them. The truck is lifted 3" with 35" tall tires.



so the current aspect ratio? I have now is



35/4. 10 = 8. 54



if I use the axles in the donor truck they have a 3:54 ratio



35/3. 54 = 9. 88 aspect ratio and that is in 4th gear. 5th gear is around 75% so in overdrive the aspect ratio would be



3. 54 * . 75 = 2. 655



35/2. 655 = 13. 18



I know the first gear in the getrag is around 5 something so getting it rolling shouldnt be a problem. I wonder if I could use 5th gear at highway speed 65 to 70 mph? Or if this truck would make a good land speed record holder? LOL



What are your opinions on these questions.....



1 Keep the getrag or loose it for a NV4500HD?



2 Keep the Dana 60's in F & R with the 4:10's and Lock Rites or install the axles from the donor truck with the 3. 54's?



3. How much power do I really need to pump out of this Cummins before it becomes a project every weekend chasing broken parts in the drivetrain?



Thanks for the input.

 

[Hutchew]

I got 3.54's and like 'em.......

BUT, I also have a 98 12v motor. With 35/12. 50/16 BFG Mud terrains, I am averaging 24-25. 5 mpg. I haven't towed with it yet, but it looks to me like I will be able to pull in the flats O/D easy, and still have plenty of power in the hills in fourth. It remains to be seen. Some people have had good luck with the Gertrag, but I would say that most have not. If I had had a thicker wallet, I would have gone for a NV5600 6-speed, but the 4500 I have works well enough for now.

I may very well be wrong, but I don't think first gen motors had a problem with the dowel pin, leading me to think Joseph might have been referring to a later model (second gen) motor. Other than that, I would say he was right on, especially about re-sealing the aft end of your engine.

Good luck with your project. That 440 is gonna be hard to match for raw brute horsepower. The payoff is gonna be the mpg's you get with the 5. 9. And the odd looks you get from people who know what a cummins sounds like

 

[Andy Perreault]

Check out Advance Adapters . For a Getrag to NV4500 swap, check out this page (you need Adobe Acrobat Reader): http://www.advanceadapters.com/acrobat/getrag.pdf

Andy

 

[CrewCabDiesel]

On your axles, go with the 3:54 gears, I was running 4:10s with a 285 tires and 79mph was about all she go. fuel milage was around 17 running highway speeds. If you want I have a line on the correct yoke for you old dana 60 rear end to run the larger u-joints for the Cummins. as for the front dana 60 u-joints are the same as the 85 gas one ton. you will need to upgrade your rear drive shaft to one to handle the cummins, one from a extended cab long box should fit your rig. I ended up turning my old gas drive shaft into one very large cork screw .



Kyle

 

[Mark_Kendrick]

What is the significance of the aspect ratio. . I've heard of it before but what is good bad . . optimal? how is the determination made?

 

[PJensen]

Cool so the 3:54's sound like they will be fine with the 35x12. 5x16. 5 tires Im running now.



What do you guys think about using a Lock Rite differential in the Front and Rear axles? Actually I really dont know if the Lock Rites are a "differential" or not.



I currently have them in the Crew Cab in the Dana 60's.



The donor truck has a Dana 70 out back and the tag on the hood calls for a 4500# axle that should be the Dana 60 right?



So I would think the front Lock Rite section coulb be used in the Dana 60 with the 3:54's from donor Diesel truck.



Will the Lock Rite from the Dana 60 rear swap into a Dana 70 rear? The 60 has a 4:10 gear and the 70 has a 3:54 gear.



Ill have to see what the dealer will charge for that driveshaft new and compare that to a third party driveshaft shop.



How much thicker is the driveshaft material on a Diesel rear driveshaft? That is kinda weird how the front driveshaft and joints are the same for the gas Dana 60 and diesel Dana 60's?

I would think the extra grunt of Low Lock and the fact that you are utilizing the front driveshaft... it would be as beefy as the rear one.



The aspect ratio thing is this Tire Diameter/Final Gear Ratio.



So on a vechicle with a 1:1 final drive in the trans the rearend ratio is the final gear ratio.



With a vechicle equipped with overdrive the final gear ratio is overdrive gearing * rearend gearing ie . 75 * 4:10 = 3. 045



35" tires / 3. 045 = 11. 49 now w/o OD 35" / 4:10 = 8. 54



26" tires/ 4:10 = 6. 34



so you can see that numerically lower aspect ratios will result in a high rpm for highway speed. What the ideal aspect ratio to shoot for depends on the vehicle and engine performance etc.



What is the "ideal" aspect ratio to shoot for with a CTD truck? Anyone know.

 

[CrewCabDiesel]

You might want to contact Valley Truck Parts in Grand Rapids MI. They are the ones who came up with the drive shaft yokes and built my drive shaft. Thier customer service is great, and they will take the time look things up for you. They built me a complete new drive shaft for around $650. They also did the rebuilding of my axles and did the gear change. The cool part was they gave me $150 back for my old 4:10 gears .



in GR, 800-783-8300 (ask for Jerry, he is the owner)

in St Joseph, MI 800-452-8808

 

[Mark_Kendrick]

Someone chime in if I'm wrong but... .



I guess opitimum aspect ratio would depend on the purpose.



staying near a stock aspect ratio that is rated for your max GCVW should get you performance and reliabilty near a stock truck.



If you were never gonna get near 20k then look at the aspect of a 3. 54 equipped truck. It would give you that trade between speed and high load capacities.



31. 5(stock tire ht for a 4x4 3500)/3. 54*. 75=11. 86



top speed is (70/2000)*3200=112 @3200rpm 2000rpm=70mph . this is a little off because I've seen 115 in my truck, but its close enough.



31. 5/4. 10*. 75=10. 24



2300rpm@70mph top speed (70/2300)*3200=97. 3 mph



to find out change in hwy rpm 2000*11. 86/10. 24=2316



I would like to cruise at 1800 rpm at 70 mph to get that I need

an aspect of (2000/1800)*11. 86=13. 71

13. 71*. 75=10. 28

10. 28*3. 54= 36. 4" tires ( the size of 22. 5" low pro truck tires)

that puts my aspect in 5th gear at 36/3. 54=10. 16, comparable to a 4. 10 in 6th gear.



The only problem is that to fit those huge cool tires I'have to have a 4-5" lift and you can forget ever hooking up a goose neck or bumper pull again let alone a 5th wheel.



To get a 4. 10 equipped truck to have the same hwy rpm as a 3. 54 truck ... x=11. 86*4. 10*. 75== 36. 4"



These calculations don't take into account the difference in hp due to changes in rotating mass (tire wt). the heavier the tire the more it takes to get it rolling and to stop it.



Sorry about the length. . I got bored and started playing w/the calculator

 

[Excessive Force]

DRIVESHAFTS

PAUL, Another contact for driveshafts,yokes,etc. is BOB at RJ's driveshaft service. excellent work and reasonable too. he also may have info on interchange of axle parts. he has a Dana 70 front axle for sale also. he did the driveshafts on my pulling truck. the number is (608) 755-4661 his shop is located in Janesville,Wi