Slant Six Forum :: Acceptable highway steep mile long hill RPM range?

. . . If you do not need the granny gear, then consider changing to a 4 speed or gearswet with more standard car gears. If you got a more 'normal' 3rd gear of around 1.4, then your RPM's in 3rd at 65 would be 3500. There are some A833's with a 1.34 3rd gear, and that would be 3350 RPM at 65.

Picked up a 1982 W150 4x4 with a slant six and 4 speed with granny gear.

For 1 mile at 60 MPH, I would not worry at all about 4000 RPM. For 10 miles straight, I suppose I might worry if the engine were not built well or was an old original engine with unknown oiling quality. I have done many 30 min track sessions where my engine only dropped BELOW 4000 for maybe 15-30 sec out of a 2-3 min lap. That's with a stock rod/cast piston motor that had loose clearances, good oil delivery and pan, and balanced bottom end components.

Lou

The older enignne is what I would worry about. But you can always rebuidl if it bows!

When I say gearset, I am not meaning front and rear axle sets; I was talking about changing out the main shaft gears and cluster gear in the transmission. If you shop around, that ought to be a lot cheaper. Do you know what model trannie you have? It wouldn't the 4 speed OD; that has a 1.4:1 4th (OD) to 3rd ratio.

And BTW the 55 MPH speed limit started in 1974, when Nixon was still in office and the Dems controlled both houses of Congress. If you ever regularly sat for 2 hours or more in line for gasoline for a period of about half a year, then it would at least make some sense for that period of time. I was feeding a '65 GTO convertible at the time!

NP435L I believe. Yes, gas lines and or no gas. My Dad had a 1969 Pontiac Grand Prix with the 455.

It looks to be quite a job to deal with transmission gears. Think I'll stick with going slow.

I have been in the van as he drove up Snoqualmie Pass here in western Washington State at 70+ MPH. Snoqualmie pass is a long grade up into the mountains. The van handles the 30-40 minute drive up into the mountains at 65-70 MPH no problem. No overheating, no knocking, no loss in oil pressure.

I agree that the easiest way to change your situation is to increase the power in the motor and swap the gears in the transmission.

Getting the trannie out with the transfer case there is a chore but once inside, it is easy...IMO...

Author:	spacecommander [ Sun Dec 21, 2014 3:15 pm ]
Post subject:	Acceptable highway steep mile long hill RPM range?
Picked up a 1982 W150 4x4 with a slant six and 4 speed with granny gear. Not much power to begin with but truck just died on hills (I'm at 5500+ feet). Put in new free flow exhaust, got cam and ported a head (not in yet), better carb system not in yet - yesterday discovered the distributor had no vacuum advance - diaphragm was shot. Replaced distributor. Helped a bit but the real problem is shown by my tachometer - 65 MPH is just 2494 RPM and hitting the hills at 65 causes the rpms & speed to drop. Hit the same hill today at 80 MPH and the truck made it up most of the way before starting to fade as 80 MPH is 3070 RPM, closer to the engine's power band. There's no easy way to re-gear as it's got both a front and rear axle. Third gear at 65 is 4140 RPM - a bit high for sustained cruising up a hill? Speed limit here in NM is 75 and if you're going 75 you're going slow. I'd like to be able to stick around 65-70. I know some engines can live at higher RPMs all day - but how will this fare at let's say 4000 RPM up a mile long hill?

Author:	nm9stheham [ Sun Dec 21, 2014 4:42 pm ]
Post subject:
Sounds like my old 1960 Ford F300 horse truck with the 292 V8. Hit the mountain grades around here and just drop it to 3rd, turn up the radio, and wait to reach the top at 45-50 mph. Even with an engine rebuild. Too much frontal wind drag, too much weight, and no good gearing step between 3rd and 4th with 1st being a granny gear. Your 3rd gear computes out to be 1.65; that is more like a 3 speed 2nd gear, which is really what you have since 1st is just for creeping with big loads. If you do not need the granny gear, then consider changing to a 4 speed or gearswet with more standard car gears. If you got a more 'normal' 3rd gear of around 1.4, then your RPM's in 3rd at 65 would be 3500. There are some A833's with a 1.34 3rd gear, and that would be 3350 RPM at 65.

Author:	spacecommander [ Sun Dec 21, 2014 5:26 pm ]
Post subject:
Quote: . . . If you do not need the granny gear, then consider changing to a 4 speed or gearswet with more standard car gears. If you got a more 'normal' 3rd gear of around 1.4, then your RPM's in 3rd at 65 would be 3500. There are some A833's with a 1.34 3rd gear, and that would be 3350 RPM at 65. I'd love that, but it's just unaffordable and undoable. I can see a fairly big transition from second (the real first) to third so the third to forth would be more usable - not sure why they made it that way. I view 4th as almost an overdrive and third as second gear, just as you said. Looks like I gotta up the horsepower and hit the hills at close to 90 - it has no problem going in the 80's on level ground - and that's with the useless 1bbl carb which will be upgraded soon.

Author:	wjajr [ Sun Dec 21, 2014 5:49 pm ]
Post subject:
Quote: Picked up a 1982 W150 4x4 with a slant six and 4 speed with granny gear. Recall 1982 was still under the spell of that stupid Carter Administration mandated 55mph national speed limit. Factory geared all vehicles in those years to putt-putt along at that mind numbing slow velocity sans fuel injection, overdrive transmissions, and low geared rear ends in the name of sipping fuel; plus the factory saved a ton of dough on speedometer numeral paint by ending dial at 75 mph. Once you get that better breathing head and torque cam installed you should notice a performance improvement.

Author:	emsvitil [ Sun Dec 21, 2014 5:54 pm ]
Post subject:
Larger diameter tires will reduce the rpm for a given mph (you'll need to change the speedo gear)

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Author:	spacecommander [ Sun Dec 21, 2014 8:52 pm ]
Post subject:
Yeah, I remember the lovely 55MPH national speed limit. Even then third gear would be high revs, 4th is only 2110. Don't miss that 55. New Mexico has 75 and that's slow here. I'm perfectly content doing 70 on the flats when there's traffic and 65 otherwise. Just don't want to be so slow that I pose a danger. If higher velocities are needed - I've got a 1986 Alfa Romeo Spider or for idiotic speed (I don't) I've got a 2010 Corvette. The camper is gone - looks like I need to update my .sig now. Cam and head will go on in the Spring when the weather is nicer and it's easier to work on things at 65 degrees or higher. Yeah, when I get new tires maybe drop down a size.

Author:	emsvitil [ Mon Dec 22, 2014 2:35 am ]
Post subject:
Dropping down in size with your tires will raise rpm. Do you want to use 3rd or 4th?

Author:	Dart270 [ Mon Dec 22, 2014 6:47 am ]
Post subject:
For 1 mile at 60 MPH, I would not worry at all about 4000 RPM. For 10 miles straight, I suppose I might worry if the engine were not built well or was an old original engine with unknown oiling quality. I have done many 30 min track sessions where my engine only dropped BELOW 4000 for maybe 15-30 sec out of a 2-3 min lap. That's with a stock rod/cast piston motor that had loose clearances, good oil delivery and pan, and balanced bottom end components. Lou

Author:	spacecommander [ Mon Dec 22, 2014 7:19 am ]
Post subject:
Quote: For 1 mile at 60 MPH, I would not worry at all about 4000 RPM. For 10 miles straight, I suppose I might worry if the engine were not built well or was an old original engine with unknown oiling quality. I have done many 30 min track sessions where my engine only dropped BELOW 4000 for maybe 15-30 sec out of a 2-3 min lap. That's with a stock rod/cast piston motor that had loose clearances, good oil delivery and pan, and balanced bottom end components. Lou Thanks. A new oil pump is in the budget anyway as the sender is screwed in cross-threaded in the present one. I'll add a pressure gauge while I'm there.

Author:	nm9stheham [ Mon Dec 22, 2014 8:05 am ]
Post subject:
The older enignne is what I would worry about. But you can always rebuidl if it bows! When I say gearset, I am not meaning front and rear axle sets; I was talking about changing out the main shaft gears and cluster gear in the transmission. If you shop around, that ought to be a lot cheaper. Do you know what model trannie you have? It wouldn't the 4 speed OD; that has a 1.4:1 4th (OD) to 3rd ratio. And BTW the 55 MPH speed limit started in 1974, when Nixon was still in office and the Dems controlled both houses of Congress. If you ever regularly sat for 2 hours or more in line for gasoline for a period of about half a year, then it would at least make some sense for that period of time. I was feeding a '65 GTO convertible at the time!

Author:	spacecommander [ Mon Dec 22, 2014 11:23 am ]
Post subject:
Quote: The older enignne is what I would worry about. But you can always rebuidl if it bows! When I say gearset, I am not meaning front and rear axle sets; I was talking about changing out the main shaft gears and cluster gear in the transmission. If you shop around, that ought to be a lot cheaper. Do you know what model trannie you have? It wouldn't the 4 speed OD; that has a 1.4:1 4th (OD) to 3rd ratio. And BTW the 55 MPH speed limit started in 1974, when Nixon was still in office and the Dems controlled both houses of Congress. If you ever regularly sat for 2 hours or more in line for gasoline for a period of about half a year, then it would at least make some sense for that period of time. I was feeding a '65 GTO convertible at the time! NP435L I believe. Yes, gas lines and or no gas. My Dad had a 1969 Pontiac Grand Prix with the 455. It looks to be quite a job to deal with transmission gears. Think I'll stick with going slow.

Author:	Reed [ Mon Dec 22, 2014 11:33 am ]
Post subject:
FYI- my brother has a 1983 Dodge B150 short wheelbase van powered by a slant six. I have upgraded it to a two barrel carb and a head with oversie valves, but those are the only mods. The van is roughly the same weight and has roughly the same aerodynamic characteristics as your truck. The van has a 1973 904 automatic trans and 3.2:1 rear axle gears. That van will cruise at 60-65 at about 2700 RPM. My brother drives like a maniac, and often gets the van over 70 MPH with the motor turning about 3000 RPM. I have been in the van as he drove up Snoqualmie Pass here in western Washington State at 70+ MPH. Snoqualmie pass is a long grade up into the mountains. The van handles the 30-40 minute drive up into the mountains at 65-70 MPH no problem. No overheating, no knocking, no loss in oil pressure. I agree that the easiest way to change your situation is to increase the power in the motor and swap the gears in the transmission.

Author:	nm9stheham [ Mon Dec 22, 2014 12:53 pm ]
Post subject:
Quote: NP435L I believe. Yes, gas lines and or no gas. My Dad had a 1969 Pontiac Grand Prix with the 455. It looks to be quite a job to deal with transmission gears. Think I'll stick with going slow. Getting the trannie out with the transfer case there is a chore but once inside, it is easy...IMO... One option would be the NP435A (never knew that existing 'til now); has a 4.56 1st and a 1.31 3rd; seems ideal if you are not rock crawling or hauling heavy stuff on the farm. Not sure how you would find or ID one.

Author:	spacecommander [ Mon Dec 22, 2014 3:36 pm ]
Post subject:
Quote: I have been in the van as he drove up Snoqualmie Pass here in western Washington State at 70+ MPH. Snoqualmie pass is a long grade up into the mountains. The van handles the 30-40 minute drive up into the mountains at 65-70 MPH no problem. No overheating, no knocking, no loss in oil pressure. I agree that the easiest way to change your situation is to increase the power in the motor and swap the gears in the transmission. Thanks. I moved to NM from Mill Creek so am very familiar with Snoqualmie pass - especially in a 1984 VW Vanagon Westfalia camper loaded to the gills and with a stock 1.9L motor and an automatic Power I can add, I have a head with OS valves and porting, taking the tranny out to swap gears - not so much.

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