Speed Limitations - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Old Chevy Mech · 12-23-2007, 11:33 AM

I was wondering what the fastest you all would go with your trucks in 4wd? My 70 Blazer with a Dana 20 I've always limited myself to 45 mph.
I have no clue what I should limit myself to with my K20 with a 4 speed & NP205 though. Any advice or experience is appreciated.

Thanks& Happy Holidays!

Frank

Blazer1970 · 12-23-2007, 11:59 AM

I have no problem driving 60 mph plus in 4WD on snowy roads. It will not hurt anything in your drivetrain - what you feel is a safe speed for the conditions is a personal decision.

70rs/ss · 12-23-2007, 05:23 PM

DEPENDS HOW SAFE YOUR RIG IS AND HOW GOOD YOUR STEERING, SUSP PARTS ARE. iF IT IS NICE AND TIGHT AND THE BRAKES WORK 70-80 IS ok (SORRY FOR THE CAPS!) It depends too on the axle ratio, 3:08 and 80 is OK, 4:11 and 55 may be the tops.

Old Chevy Mech · 12-24-2007, 04:38 AM

Thanks Guys!
My Dad always limited the speed in our 4x4 70 Jimmy to 45 mph for whatever reason so that "number" stuck with me. I've not found anything in writing that says anything about speed limitations on the drive train one way or the other so thats why I'm asking.

Thanks!
Frank

cobinder · 12-24-2007, 12:27 PM

My thought is, the more miles you have on your drivetrain without replacing some of the parts that wear out (u-joints, hub needle bearings,etc) the more you need to consider how fast you want to go when locked in 4wd. If at 50mph the noise from your drivetrain exceeds the 3/4 sound level on your stereo, you might want to back her down a bit.
The faster you go the higher the chance a worn part will have a failure.

Old Chevy Mech · 12-29-2007, 05:53 AM

The drive train is tight, I was just wondering if there was a GM recommendation on speed limit while 4wd was locked in. I believe some older international scouts had warnings not to exceed 45mph while in 4wd, but then I dont think those old scouts would do over 55 on a flat anyway. I dont understand why unless the transfer case cant handel it. I think most of them had dana 20 cases, they just had the rear output shaft coming out the lower end. My Blazer has the Dana 20, thats why I'm wondering...

Frank

**Yukon Jack** · 12-29-2007, 06:14 AM

Am I assuming correctly that you are talking about going those speeds on snow packed roads?

You wanted to stay out of 4wd when the roads are mostly clear as the Dana 20 and NP205 you list won't allow any differentiation between the two axles. You can bind up your driveline if there isn't any way for the axles to slip a little bit.

Old Chevy Mech · 12-29-2007, 11:10 AM

Yes, I was thinking snow, dirt or gravel only. Just didnt say that! LOL

Frank

12-23-2007, 11:33 AM	#1
Old Chevy Mech Keepin it runnin! Join Date: Oct 2007 Location: Deep River, CT Posts: 1,036	Speed Limitations I was wondering what the fastest you all would go with your trucks in 4wd? My 70 Blazer with a Dana 20 I've always limited myself to 45 mph. I have no clue what I should limit myself to with my K20 with a 4 speed & NP205 though. Any advice or experience is appreciated. Thanks& Happy Holidays! Frank __________________ 1970 K-5 4X4 Blazer 1970 K-20 4X4 Long Bed "Liberty Means Responsibility, that is why most men dread it" Last edited by Old Chevy Mech; 12-29-2007 at 05:56 AM.

12-23-2007, 11:59 AM	#2
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	Re: Speed Limitations I have no problem driving 60 mph plus in 4WD on snowy roads. It will not hurt anything in your drivetrain - what you feel is a safe speed for the conditions is a personal decision. __________________ Tim

12-23-2007, 05:23 PM	#3
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,270	Re: Speed Limitations DEPENDS HOW SAFE YOUR RIG IS AND HOW GOOD YOUR STEERING, SUSP PARTS ARE. iF IT IS NICE AND TIGHT AND THE BRAKES WORK 70-80 IS ok (SORRY FOR THE CAPS!) It depends too on the axle ratio, 3:08 and 80 is OK, 4:11 and 55 may be the tops. Last edited by 70rs/ss; 12-23-2007 at 05:24 PM.

12-24-2007, 04:38 AM	#4
Old Chevy Mech Keepin it runnin! Join Date: Oct 2007 Location: Deep River, CT Posts: 1,036	Re: Speed Limitations Thanks Guys! My Dad always limited the speed in our 4x4 70 Jimmy to 45 mph for whatever reason so that "number" stuck with me. I've not found anything in writing that says anything about speed limitations on the drive train one way or the other so thats why I'm asking. Thanks! Frank __________________ 1970 K-5 4X4 Blazer 1970 K-20 4X4 Long Bed "Liberty Means Responsibility, that is why most men dread it"

12-24-2007, 12:27 PM	#5
cobinder Everything is work in progress Join Date: Apr 2006 Location: Denver Colorado Posts: 326	Re: Speed Limitations My thought is, the more miles you have on your drivetrain without replacing some of the parts that wear out (u-joints, hub needle bearings,etc) the more you need to consider how fast you want to go when locked in 4wd. If at 50mph the noise from your drivetrain exceeds the 3/4 sound level on your stereo, you might want to back her down a bit. The faster you go the higher the chance a worn part will have a failure. __________________ Good luck with your truck! How much?! It's just an old truck part!! 49 International on a 80 GMC 3/4ton 4x4 chassis 48 International KB-5 2 ton dump bed 04 Honda CRF "500" 09 Honda CRF450 fuel injected rocket 03 Suzuki hayabusa carbonfiber wheeled monster. 02 Ford diesel stretch van (toy hauler) 01 38' Monaco diesel pusher motorhome

12-29-2007, 05:53 AM	#6
Old Chevy Mech Keepin it runnin! Join Date: Oct 2007 Location: Deep River, CT Posts: 1,036	Re: Speed Limitations The drive train is tight, I was just wondering if there was a GM recommendation on speed limit while 4wd was locked in. I believe some older international scouts had warnings not to exceed 45mph while in 4wd, but then I dont think those old scouts would do over 55 on a flat anyway. I dont understand why unless the transfer case cant handel it. I think most of them had dana 20 cases, they just had the rear output shaft coming out the lower end. My Blazer has the Dana 20, thats why I'm wondering... Frank __________________ 1970 K-5 4X4 Blazer 1970 K-20 4X4 Long Bed "Liberty Means Responsibility, that is why most men dread it" Last edited by Old Chevy Mech; 12-29-2007 at 05:56 AM.

12-29-2007, 06:14 AM	#7
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,686	Re: Speed Limitations Am I assuming correctly that you are talking about going those speeds on snow packed roads? You wanted to stay out of 4wd when the roads are mostly clear as the Dana 20 and NP205 you list won't allow any differentiation between the two axles. You can bind up your driveline if there isn't any way for the axles to slip a little bit. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

12-29-2007, 11:10 AM	#8
Old Chevy Mech Keepin it runnin! Join Date: Oct 2007 Location: Deep River, CT Posts: 1,036	Re: Speed Limitations Yes, I was thinking snow, dirt or gravel only. Just didnt say that! LOL Frank __________________ 1970 K-5 4X4 Blazer 1970 K-20 4X4 Long Bed "Liberty Means Responsibility, that is why most men dread it"



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