CUCV axle ratio?

[BluTrukker]

I am looking to do a 68 4x4 project. Build a good solid wood hauler, not a show truck. I have an opportunity to get the entire driveline out of a 1987 military CUCV pickup. The seller says the front and rear axles are both 5:1 ratios. Does that sound right? I know the military trucks have heavy duty axles, but the number sounded odd. I've never seen an even number like that. I'm guessing they are 4.56 or somkething like that. Did all CUCV's have the same axles?

[thirdstreettito]

That guy is dead wrong, no such thing as 5:1 gears. A CUCV M1008 has 4:56 gears, locked in the rear, open in the front. A CUCV M1009(blazer) has 4:10 gears posi rear open front. IIRC.

[48cj2a]

If its a pickup with D60 and 14bolt it will be 4.56 with a detroit in the rear. If the truck has the NP205 transfercase it could also have a Tracloc in the front other wise its an open carrrier.

All the Blazers have 3.08s with a GovLoc in the rear.

[496 BB]

Originally Posted by 48cj2a

If its a pickup with D60 and 14bolt it will be 4.56 with a detroit in the rear. If the truck has the NP205 transfercase it could also have a Tracloc in the front other wise its an open carrrier.

All the Blazers have 3.08s with a GovLoc in the rear.

Dead on.

[thirdstreettito]

Originally Posted by 48cj2a

If its a pickup with D60 and 14bolt it will be 4.56 with a detroit in the rear. If the truck has the NP205 transfercase it could also have a Tracloc in the front other wise its an open carrrier.

All the Blazers have 3.08s with a GovLoc in the rear.

I couldn't remember exactly what the M1009's had!

[48cj2a]

If it were not the fact I drove um for years and was a Chevy 4x4 lover I would not have known.

[BluTrukker]

Thanks for the quick response. next question. If I leave the front axle as is, and drop 3.08 on the rear, would that cause a large explosion in the transfer case in 4 wheel drive? I would like to keep the rpms down on the highway to save the 6.2.

[48cj2a]

The front and rear need to match within at least 1 tooth.

If you can get the 1 ton drivetrain with the 4.56 gears you can compensate the RPMs two ways. Get an OD transmission like a 700R4 if auto or a 5spd if manual and go with a 35" or larger tire.

If the trannys not in the budget then plan on a lift and bigger tires for sure.

[Prerunner1982]

Depending on the ratios in the front and rear you can run different sized tires to compensate.

[496 BB]

Originally Posted by BluTrukker

Thanks for the quick response. next question. If I leave the front axle as is, and drop 3.08 on the rear, would that cause a large explosion in the transfer case in 4 wheel drive? I would like to keep the rpms down on the highway to save the 6.2.

You can do it that way but CAN NOT drive in 4wd on any hard surfaces. It would be strictly for MUD applications only. Ive seen it many times in mud runners set up like this but will not work at all on street.

If your wanting numerically lower gears then you could EASILY sell that setup for around $1500 for both and get a 14 bolt FF and a dana 44 (or corporate 10 bolt) for under $500 with the gears you want in em.....most likely a 3.73 setup. Hell I'll trade you straight up if you want????

[GM72K10]

Originally Posted by 48cj2a

If its a pickup with D60 and 14bolt it will be 4.56 with a detroit in the rear. If the truck has the NP205 transfercase it could also have a Tracloc in the front other wise its an open carrrier.

All the Blazers have 3.08s with a GovLoc in the rear.

Plain M1028s with NP208s also have traclocs in front. M1028a1s (np205) and M1031s (NP205) also have traclocs in front.

[87 V20 Scottsdale]

Not trying to hi-jack the thread, but what is the difference in trucks with the NP208 and the NP205 cases? Sorry I don't know much about the CUCV's.

[GM72K10]

Log on to www.steelsoldiers.com
best place to learn about CUCV and MVs

[48cj2a]

208s are a chain driven T/C, 205s are a all gear driven T/C and considerd HD and nearly bullet proof within reason.

As for the Trac Loc in the front - If you had a HD in the VIN vs GD (i.e 1GBHD vs 1GCGD) you will most likely have a TracLoc which would also have come from the factory with a THM400/NP205 T/C, If you run across one with a 208 it was most likely swapped in later and is not common by any means. The ones to look for are the Contact Maintenance M1031s they even have a PTO on the side of the NP205 T/C.

Some of the Dooley Conversions done on a M1008 or vanilla 1028 shelter carrier could have a 208 but most likely does not have a TracLoc.

My unit converted 4 to duallys in the mid 80s to support the TRC-170V3 Troposcatter Microwave Communication System (in a S-250 shelter)

[87 V20 Scottsdale]

Originally Posted by 48cj2a

208s are a chain driven T/C, 205s are a all gear driven T/C and considerd HD and nearly bullet proof within reason.

I meant what was the reason for the trucks having different cases, the only ones I've ever been around had NP208's.

[48cj2a]

HD applications,

I'm no engineer but when the Military requires the vehicle to be used for specific applications they would want the heavier options, Just like the transmissions used today by GM: 4L60E or 4L80E.

[GM72K10]

Originally Posted by 87 V20 Scottsdale

I meant what was the reason for the trucks having different cases, the only ones I've ever been around had NP208's.

NP205s have a pto provision which was needed in the contact maintenance trucks to run auxilary equipment. (generator)
My M1028a1 I converted into a pickup from a truck similar to the first one. The one pictured I used to own, it was a true M1031 with a NP205 and a pto. Also, all Contact maintenance trucks are NOT M1031s, some are just plain M1028s with NP208s.