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Open Roads Forum  >  Tow Vehicles

 > Do I have have enough Truck?

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b1jetmech

Wichita

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Posted: 06/27/21 02:03pm Link  |  Quote  |  Print  |  Notify Moderator

Hello All,

My first post and good to meet you all.

we're getting back into RV and traveling.

Have an important question regarding towing heavy fifth wheel.

We picked up a 04' Keystone Sprinter 350 FWBHS and it has a UVW of 9,700 lbs. and a GVWR of 12,500 lbs at a length of 41 ft.


The tow vehicle is a 1995 Chevy K3500 CC SRW with a GVWR is 9,200 lbs with 4.10 gears. I have plans to upgrade the engine/transmission to a Cummins 5.9/Allison 6 speed combo for I do engine conversions. I know that powertrain combo is more then adequate but is the rest of the truck capable such as the brakes?

The rear axle is rated at 6089 lbs but the overall GVWR might not be enough to accommodate the pin weight of 2000 lbs plus passenger and cargo.

After all said and done, will this truck be stable enough to tow this fifth wheel long distances and through mountains and so forth?

Has anyone towed a heavy trailer with a 88-98 GMT-400 chevy?

Second Chance

Wherever...

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Posted: 06/27/21 02:27pm Link  |  Quote  |  Print  |  Notify Moderator

Loaded, the pin weight for that trailer is more likely to be in the 2,500 - 2,800 lb. range. I would suggest weighing the truck (full tanks and all occupants), add 150 lbs. for a hitch over the rear axle, and see what you have left over on the rear axle and tire ratings.

Rob


U.S. Army retired
2020 Solitude 310GK-R
MORryde IS, disc brakes, solar, DP windows
(Previously in a Reflection 337RLS)
2012 F350 CC DRW Lariat 6.7
Full-time since 8/2015


BenK

SF BayArea

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Posted: 06/27/21 03:00pm Link  |  Quote  |  Print  |  Notify Moderator

Welcome to the forum !

Mine is a 1996 K3500, 7.4L Suburban with 4.1’s. Upgraded brakes to be similar to yours. Only thing not upgraded to like yours is the front disc & friction material (not as thick, but swept area is about the same).

Am not going to comment on a fiver, as don’t have much experience with them. Just played around with them helping church members figure out their issues.

First, our rear axles are from AAM and AAM rates it at 10,000 GAWR. GM rates ours at 6K GAWR. Don’t know whether spring pack, brakes, or ??? Dodge of same era also uses that same AAM axle.

Brakes on GMT400 in stock form is barely okay when up to snuf. Can be made to be very good to GREAT. Dodge of same ear also used similar front brakes and also had problems.

Main issue is the caliper slide assembly, over time, stick. Key to knowing that is to check if one side friction material is wearing out faster than the opposite side. What happens is that the caliper assembly sticks and locks one side so it is misaligned. (Edit…had to change to ‘locks’…bad word filter forbid he word initially used)

Solution is to super tune the caliper slide assembly, if you haven’t yet.

Get OEM rebuild kit and be sure to use the new O-rings. Tough to get them installed and know many who just give up and toss them.

I use Sta-Lube high temp brake grease that has a high amount of Molybdenum Sulfide pre-mixed. Mix it with Mobil 1 to reduce the viscosity a bit.

Generously coat the O-Rings and the slide bore/tube with above grease.

Poke in the slide tube and almost poked out the other side. Almost, so as to allow filling that cavity between the tube and cast iron bore. Leave some air, as too much will have it expand and leak.

Then assemble as per manual and use the highest performance (hardest) friction material you can find. They will make much more noise, but that is the way of performance friction material. Doesn’t bother me, as know I have nose bleed brakes…have out stopped a sedan where they just barely rear ended me.

The G80 locker is a clutch type from Eaten. Ours has a governor set too high before it tosses in that clutch to lock. Newer governor is set at around 200 RPM differential. Older will lock with too much differential (and much more power) RPMs and grenades the diff.

1995 has the thermal safety set higher than mine and will go into the various limp modes too soon. Buddy removed the main thermo set point on his 1995 K3500 Suburban and it be got both higher MPG & stay longer in power mode. Along with a 180*F thermostat (mine too) get power mode most times when nailing the throttle.

Don’t know what your tuner will do with the Cummins & Allison, but they should know all that.

Designed a AFT aux cooler mounted midship for him. on my list, but haven’t done it yet.

Two 45,000 lb rated plate ATF coolers with an electric radiator fan. Didn’t put in a bypass valve and just made sure the ATF also ran into & through the main radiator.

His dash coolant temp gauge drop like a rock when that external ATF cooler’s fans turned on.

He towed an approx 10,000 lb trailer.

Assume you have heard of the DuraBurb with a Duramax diesel/Alison combo. Should be lots of info that applies to your planned Cummins/Alison combo.

Good luck and report back on this thread !


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

blt2ski

Kirkland, Wa

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Posted: 06/27/21 03:40pm Link  |  Quote  |  Print  |  Notify Moderator

Hour RA is rated at 6080 lbs, which equals the stock tires. Springs are good to 6400, axle as noted 10,000.
Reality, a tire upgrade, common is a 265-75-16, nets you 6800 or so lbs of tires. RA on my 88 and 96 K3500 were 2200-2400 empty. Around 3000 lbs to put on RA before overloading things.
A dually version has a 7500 RA. You could do as I did to the 96, install a 6/1 spring pack vs stock 5/1, make them about 1/16-1/8" thicker, you have 8500 lbs of springs.....
A few things and yes you could handle family and hitch wieght. I would swag going to be 2500-3000 lbs as noted. 20-25% of gross wieght.

Marty


92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
2014 Chevy 1500 Dual cab 4x4
92 Red-e-haul 12K equipment trailer

ksss

Eastern Idaho

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Posted: 06/27/21 03:43pm Link  |  Quote  |  Print  |  Notify Moderator

BenK mentioned it, but having had a handful of GMT trucks that I towed with and the brakes suck in stock form. I would for sure budget to upgrade them.


2020 Chevy 3500 CC 4X4 DRW D/A
2013 Fuzion 342
2011 RZR Desert Tan
2012 Sea Doo GTX 155
2018 Chevy 3500HD CC LB SRW 4X4 D/A
2015 Chevy Camaro ZL1

b1jetmech

Wichita

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Posted: 06/27/21 05:28pm Link  |  Quote  |  Print  |  Notify Moderator

Second Chance wrote:

Loaded, the pin weight for that trailer is more likely to be in the 2,500 - 2,800 lb. range. I would suggest weighing the truck (full tanks and all occupants), add 150 lbs. for a hitch over the rear axle, and see what you have left over on the rear axle and tire ratings.

Rob


Hi Rob,

Yeah, I need to find a DOT scale to weight the truck and weigh it again with the trailer and all occupants. I do have a feeling it will be well over the payload capacity. We'll see.

b1jetmech

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Posted: 06/27/21 05:31pm Link  |  Quote  |  Print  |  Notify Moderator

BenK wrote:

Welcome to the forum !

Mine is a 1996 K3500, 7.4L Suburban with 4.1’s. Upgraded brakes to be similar to yours. Only thing not upgraded to like yours is the front disc & friction material (not as thick, but swept area is about the same).

...

Assume you have heard of the DuraBurb with a Duramax diesel/Alison combo. Should be lots of info that applies to your planned Cummins/Alison combo.

Good luck and report back on this thread !


Hey, thanks for the info. I have heard of brake calipers sticking which of course causes one pad to wear more then the other. Will have to be cautious of that.

I did see a brake upgrade by using K3500 "dually" rotors, pads and calipers. Even though my truck is a one ton, it doesn't have the braking as the dually does.

I'll keep you posted.

b1jetmech

Wichita

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Posted: 06/27/21 05:35pm Link  |  Quote  |  Print  |  Notify Moderator

blt2ski wrote:

Hour RA is rated at 6080 lbs, which equals the stock tires. Springs are good to 6400, axle as noted 10,000.
Reality, a tire upgrade, common is a 265-75-16, nets you 6800 or so lbs of tires. RA on my 88 and 96 K3500 were 2200-2400 empty. Around 3000 lbs to put on RA before overloading things.
A dually version has a 7500 RA. You could do as I did to the 96, install a 6/1 spring pack vs stock 5/1, make them about 1/16-1/8" thicker, you have 8500 lbs of springs.....
A few things and yes you could handle family and hitch wieght. I would swag going to be 2500-3000 lbs as noted. 20-25% of gross wieght.

Marty


Hi Marty,

That is an ideal installing heavier springs such as "dually"? That would make for a stiff ride empty but would help in RA load. I'll look into that...call my axle guy tomorrow to see what they cost.

b1jetmech

Wichita

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Posted: 06/27/21 05:37pm Link  |  Quote  |  Print  |  Notify Moderator

ksss wrote:

BenK mentioned it, but having had a handful of GMT trucks that I towed with and the brakes suck in stock form. I would for sure budget to upgrade them.


The only upgrade I seen for an existing one ton would be upgrade to "dually" brakes for they are wider and have larger calipers, along with larger wheel cylinders in the back. As of now, I could not find any after market set up. Will keep searching, thanks fort the input.

Chase

b1jetmech

Wichita

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Posted: 06/27/21 07:29pm Link  |  Quote  |  Print  |  Notify Moderator

Is there a way to post pictures directly from the computer? I don't have a picture host anymore. Would like to upload some pics.

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