1976K5Chalet
Observer
What did you source the hydro boost out of?
Larry's 1978 K10
- Thread starter Larry
- Start date
Oilbrnr
Active member
Some of us know who wears the pants in that household...
zoomad75
K5 Camper guy
We were talking about that option in our last BS session. I don't think it's an option as it's not available on the JB conversions website. Ideally is option is going with an early nv4500 with the better granny gear ratio or an ORD magnum or NWF black box/eco box reduction unit between the existing 4500 and 205. Neither option is cheap.
Currently, with a late 4500, 205 and 4.56 gears, he's got a 50:1 crawl ratio. When my 4500 swap is done, using the late style trans, 241 and my 4.10 gears I'll be at 62:1. Even with changing to the early 4500 with the deeper first gear the crawl ratio only goes up to 57:1. Swapping out a stock 205 for a Lomax unit would bump it all the way up to 76:1, but isn't currently available. Now adding in a Magnum or NWF box which both use the 241's planetary gearset at 2.72:1 ratio would kick up the double low crawl ratio to an insane 137:1. Or he unloads the 205 for a 241 which would bring the crawl ratio in at 69:1.
Keep in mind the use of the truck is not pure rock crawling. But we do see some serious descents down mountain shelf roads or dropping into valleys in the desert. The low gearing is to maintain a slow controlled climb down with very little use of the brakes. The bonus is when we do get into some rocks and let the gears do the work.
I suppose from the discussion so far an Atlas transfer case is not in the consideration set. I have an Atlas II with a 3:1 ratio, NV4500 first gear of 5:61, and 4.56 gears for a crawl ratio of 76:1. If that isn't good enough, one could get a 5:1 Atlas II that would provide a 130:1 crawl ratio.
An Atlas 4 would provide five options of 3 separate low range gear ratios:
1.0:1 / 2.72:1 / 1.50:1 / 4.08:1
1.0:1 / 2.72:1 / 2.00:1 / 5.44:1
1.0:1 / 2.72:1 / 3.00:1 / 8.16:1
1.0:1 / 2.72:1 / 3.80:1 / 10.34:1
1.0:1 / 2.72:1 / 4.3:1 / 11.69:1
The final choice would provide crawl ratios of 70, 110, or 300!
An Atlas 4 would provide five options of 3 separate low range gear ratios:
1.0:1 / 2.72:1 / 1.50:1 / 4.08:1
1.0:1 / 2.72:1 / 2.00:1 / 5.44:1
1.0:1 / 2.72:1 / 3.00:1 / 8.16:1
1.0:1 / 2.72:1 / 3.80:1 / 10.34:1
1.0:1 / 2.72:1 / 4.3:1 / 11.69:1
The final choice would provide crawl ratios of 70, 110, or 300!
nitro_rat
Lunchbox Lockers
If the lo max isn't available I guess a 241 is the logical choice!
TwinDuro
Well-known member
I've been enjoying the heck out of your builds and adventures Larry! The new K5 build is looking mighty fine! I have some questions about your 9.5" 14-bolt SF and locker selection that have been bugging me for quite some time that I was wondering if you had any insight on since you're traveling down a similar path. I'm currently building up a six-lug 9.5" SF for the rear of my '92 K1500 RCSB (with a factory MT8 NV4500, TBI 5.7 combo). When they were still available, my plan was to buy a new aftermarket Eaton E-locker. Of course, now that those are discontinued (I'm glad the service kits are still available though), robbing the factory e-locker from a H2, just like you mentioned for your K5, was my next course of action. I've seen quite a few lower-mile complete H2 complete rear axles on eBay, freight included, for around $500.
Where I'm going with this is do you think there would be any chance the factory AAM 9.25 Trac-Rite EL locker (OEM Dodge PN: 05175278AB) from the front of a PowerWagon would be compatible/appropriate to use in the rear of a GM 9.5" SF? On paper, it looks plausible (33 spline axles), although the the carrier design of the AAM 9.25 looks less beefy then the Eaton E-locker found in the H2, to me, but it's probably an illusion on my part.
Just curious if this is something you've thought about. Cheers!
Where I'm going with this is do you think there would be any chance the factory AAM 9.25 Trac-Rite EL locker (OEM Dodge PN: 05175278AB) from the front of a PowerWagon would be compatible/appropriate to use in the rear of a GM 9.5" SF? On paper, it looks plausible (33 spline axles), although the the carrier design of the AAM 9.25 looks less beefy then the Eaton E-locker found in the H2, to me, but it's probably an illusion on my part.
Just curious if this is something you've thought about. Cheers!
nitro_rat
Lunchbox Lockers
As far as I know the Chevy 9.5 ring/pinion/carrier will interchange with the Dodge AAM 9.5 front axle. The Dodge AAM 10.5/11.5 rear parts will not interchange with Chevy 10.5/11.5!
I run a 9.5 sf with a Gov-Lock and Spartan lunchbox locker up front in my old Suburban and I am VERY happy with that combination. The 9.5 Gov-Lock is much beefier than the 8.5 Gov-Bomb! If you know what you have you know not to shower down when one wheel has no traction anyway...
I run a 9.5 sf with a Gov-Lock and Spartan lunchbox locker up front in my old Suburban and I am VERY happy with that combination. The 9.5 Gov-Lock is much beefier than the 8.5 Gov-Bomb! If you know what you have you know not to shower down when one wheel has no traction anyway...
Larry
Bigassgas Explorer
Just another square body with hydroboost. Most 1 tons, big blocks and diesels had hydroboost.
Nah, I wouldn’t go backwards on the Tcase to a 241. Not that 241’s are bad, they just aren’t as the anvil a 205 is. I have a 241 behind a NV4500 in my Burb and it works great with a respectable low range. If anything, go with the Tremec TR-4050 with a 6.16 granny for the K10. It’s a direct bolt in for a NV4500. GM has been using the TR-4050 in full size trucks for the Latin American market for around 10 years already.
Exactly what nitro rat said
nitro_rat
Lunchbox Lockers
I've never heard of the Tremec but I've mostly been banging around with the same old stuff all these years. Is there an application in the US market for that trans?
Larry
Bigassgas Explorer
Nope, nobody offers a manual transmission in full-size trucks anymore in the US (RAM was the last in 2019) but a new crate Tremec TR-4050 can be had from these guys…. Or try to smuggle on up from Mexico out of a late model GM 4x4. They are much like a NV4500 and come in 2wd and 4wd flavors, although they have an aluminum housing. This one happens to be a 2wd version
And 4x4
nitro_rat
Lunchbox Lockers
Nope, nobody offers a manual transmission in full-size trucks anymore in the US (RAM was the last in 2019) but a new crate Tremec TR-4050 can be had from these guys…. Or try to smuggle on up from Mexico out of a late model GM 4x4. They are much like a NV4500 and come in 2wd and 4wd flavors, although they have an aluminum housing. This one happens to be a 2wd version
And 4x4
I work in Mexico sometimes, I guess I need to get a bigger suitcase...
1976K5Chalet
Observer
Reason i ask...i scored a cucv (mid 80's) booster (nos uncle gm in the silver wrapper) for dirt. My RV series bible did not show a different pedal assm in 90/91 for hydro....so i am hoping when i get that far it will bolt in and the rod will hook to the pedal with no fuss or muss.
Larry
Bigassgas Explorer
You will need a different brake pedal for hydroboost as the connection hole is in a different spot. Those pedals aren’t super hard to come by as there are may CUCV parts sellers out there or comb the junkyards for a squarebody with hydroboost. But, there will be a few bigger challenges as 1981 and later trucks used metric threads while 1980 and older had SAE threads. The CUCV hydrobooster will have metric threads but if your truck is 80 or older the steering gear and power steering pump will be SAE, so you’d have to have special hoses made or build your own out of AN fittings/hose. The second challenge would be if the NOS hydrobooster doesn’t have the firewall bracket already attached to it you’ll have to go buy a junkyard booster from a squarebody to get that….and the bracket is a PITA to change due to the odd nut and location of the nut that holds it on. Its not fun to get that nut on and off.
All this can be overcame though. I’ve done it a couple times. My K10 had to have special hoses made with the booster and power steering pump being metric and steering gear being SAE. I really wish I would have just swapped on a later metric steering gear at that time (or made my own AN hoses) because if I have a hose failure on the road it won’t be as easy as waltzing into Napa to get another.
TwinDuro
Well-known member
Thanks a million nitro_rat and Larry, great info! Also, very interesting on the TR-4050. Before they folded and combined into Four Wheeler Magazine (ending of an era), Petersen's 4 Wheel and Offroad had a short blurb on the TR-4050 but the info they had was limited to the specific swap they were completing. I didn't realize it is a direct bolt in for the NV-4500, the specs look nice and the gearing is much closer to the early GM NV4500 but without the non-synchronized 1st/reverse gears. I like the looks of the 3.11:1 2nd gear was well. I'm also happy to see the "Dexron III" fill sticker on the side. Not that its a big deal at the end of the day, but it always hurt to spend close to $100 on a gallon of Castrol Syntorq when refilling the 'ol NV.