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My 81 Crew

J

jayman83706

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Hi all. I'm new to the site (well kind of..)
I have an 81 crew cab 4x4 that is my daily driver and a project (i'll post some pictures soon). When i bought the truck it had a dana 44 front axle which was upsetting but i bought it anyways. (always wanted one)
Anyways, i am ordering a new set of 1 ton axles on Monday. They are the CUCV's with 4.56 gears. I have 35 inch tires with a th400 tranny. Will this be geared to low for the street? I was thinking about maybe buying a 700r4 if it would help. Any thoughts?
My plan is also to replace the 454 with a Cummins. Which is the best year of the 5.9 turbo? Will it be alright with the 700r4?

Sorry for all the questions. It has been a while since i have owned an old Chev so any help and opinion is welcomed.
 
Fellow '81 crew cab'er here.:thumb: 4.56's with 35's will be perfect with your Th400.

I think you'd have a better chance making 10 bolt axles live under a rock crawler with 44" boggers than making a TH700R4 last behind a mild Cummins.:whistle:

The best years are 91-2007, literally.... they are all good. For ease of installation I would look for a 91-97 though, because late '98's were electronic so you'd have a computer system to incorporate into the truck. 93 and older will be the older motor with the VE rotary pump. Good engine, but you are limited to around 350HP or so, IIRC, because that VE pump has it's limits. the 94-97 (early 98 actually) is the best if you want to make some serious power, if you don't want to get into the later years that are electronic. The 7100 pump found in those years is a very robust unit capable of moving a massive amount of fuel.

You'll want to address that D44 before a Cummins swap though, as I would tend to think you'd eat ball joints and wheel bearings with the weight of the Cummins, combined with your larger 35's.
 
Thanks for the reply. The dana 60 is coming for sure. Just doesn't seem right having a 44 under a 1 ton truck.
What rpm do you think it will run at highway speeds? Should i bump up to 37's (all i need is an excuse lol)
I definately don't want to deal with the computers so i think i will start looking for one around 91-97. Thanks again.
 
Welcome!
I just put a cummins in my 79. I went with the 94 with the p7100 pump. It sure was a fun conversion, I just drove it down the road for the first time last week.

My opinion is to not go with the 700r4. First of all you will need to adapt it to the cummins and it would have a hard time with the torque of the cummins. If you plan on staying stock with the engine, the stock transmission in the dodge will handle the job.

Eve have any questions with the swap, let me know b
 
A 700r4 will fail behind a cummins for sure. The stock dodge cummins automatic is pretty weak as well. Your best bet is an nv4500 5 speed.
 
That's why I said if he keeps the motor stock the auto would be alright. They aren't the best trannys in the world, but it would be a much better option.

On that note, NV4500 all the way
 
Thanks again for the replies. It's nice to have such knowledgeable folks that are willing to help. I would love to go the NV4500 but i guess i always figured that installing a clutch pedal would be difficult. On second thought though it probably bolts right up. Has anyone done this? That would definately be my ideal route to go.

1976Blazer76....I will probably take you up on that offer a lot during this process. You will be sick of me in no time lol.

Did the nv4500 ever come stock behind a Cummins? Just wondering what kind of donor trucks to look for. I would rather buy new but the almighty wife has me on a pretty strict budget. I'm sure the budget will go out the window when we get to her project. We sold our 72 Blazer years ago and she wants another one when i finish mine.
 
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The nv4500 did come stock behind the cummins starting in 94. The issue I then ran into was mating up a passenger drop np205. I ended up converting my nv4500 to 2wd and ran a divorced transfer case.

Best thing I did in the whole process was get a running donor truck. For me it was good to have the peace of mind knowing I was working with an engine that already ran well. Plus, I was able to sell off the extra parts and make a good chunk of my money back
 
Nazarethk5 said:
The stock dodge cummins automatic is pretty weak as well.
Click to expand...

Quite the contrary actually.... everyone thinks a TH400 is bomb proof, but if they had come with a Cummins in front of it instead of a weak 454 in comparison, the Th400 wouldn't have it's good reputation.

Amazingly, my stock 48RE is managing fine with over 500HP and nearly 1000 ft lbs in front of it.:doah: That kind of power would tear a 4L80E apart.
 
Well in his year range it would be the 47re which I have absolutely never heard anyone say any good about.
 
Nazarethk5 said:
Well in his year range it would be the 47re which I have absolutely never heard anyone say any good about.
Click to expand...
In his year range it will be a 518 or 47RH, but splitting hairs really. The newer 48RE is only marginally stouter than the earlier versions.

My 47RE in my '01 has been a good transmission. I know of a couple guys with stock 47's still with a Smarty programmer. There... now you've heard something good about a 47RE.:D
 
1976Blazer76 said:
The nv4500 did come stock behind the cummins starting in 94. The issue I then ran into was mating up a passenger drop np205. I ended up converting my nv4500 to 2wd and ran a divorced transfer case.
Click to expand...

Just run a GM NV4500 (96 or newer) with a Dodge input shaft (may as well upgrade to a 1 3/8" ) and then use a round pattern NP205. You can use a short input 205 and bolt it directly to the nv4500 or use a long input 205 wich will require a spacer/adapter to mount to the trans.
You could also use a Dodge 4500 and a dodge 205, but that would require finding the t-case from an 89-93 (IIRC) cummins truck. These trucks used the getrag tranny but had a 29 spline pass. side drop 205 that will mount behind a Dodge nv4500.
I personally went the GM 4500 route with a GM 205 short input to keep my drivetrain as short as possible since it's in a K5.
 
How bout the clutch pedal. Can i just yank one out at the junkyard and bolt it straight up? Anyone ever tried it?
 
I see why you are defending the dodge automatic but I still think they are crap. You can use the clutch pedal out of our year stick trucks.
 
No didnt want one. Too many buddies with cummins cursing those things. I'd rather have a stock nv4500 with a decent clutch then spend a couple grand to beef up the automatic. I really don't feel like arguing with you.
 
rjfguitar said:
Quite the contrary actually.... everyone thinks a TH400 is bomb proof, but if they had come with a Cummins in front of it instead of a weak 454 in comparison, the Th400 wouldn't have it's good reputation.

Amazingly, my stock 48RE is managing fine with over 500HP and nearly 1000 ft lbs in front of it.:doah: That kind of power would tear a 4L80E apart.
Click to expand...


That is why the Duramax can only be had with the Allison, the 4L80 in factory form, didn't have the capabililty or the future to handle more than 500ft lbs.
 
I used the stock dodge clutch master and slave cylinder. You just need to adapt the firewall to hold the dodge master cylinder.
 
1976Blazer76 said:
I used the stock dodge clutch master and slave cylinder. You just need to adapt the firewall to hold the dodge master cylinder.
Click to expand...

That's what we did. It was a PITA but it made everything else easier. We even used the steering column and wiring harness out of the donor truck.

What are people using for a clutch with the NV4500 to the Cummins?
 
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