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Junior Member
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Discussion Starter #1
Happy 4th everyone!

I was wondering if anyone knew how to determine the gross combined weight rating for my tow truck. Its a 1991 4700 with a dt360, 5 speed stick, and 10r22.5s. It has a gross weight of 25500, and weighs 15500 unloaded. I realize I cannot have more than 10K pounds on the rear axle, but what determines how much I can pull. I tow f550 bucket trucks and empty 25 foot box trucks most often, but can I tow a truck with a gross weight thats more than mine, like a 33K pound dump, if the front axle weight is 10k or less? Thank you very much for the help and recommendations.
 

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You can get the Gross Combined Weight Rating from the IH dealer, but I'd say probably right at 40k. Towing another truck may be a whole different story. Our 4900s at work have a GVWR of 33k, and a GCWR of 48,500. I'd highly suggest a 10-13speed swap to get more gear out of that little 360.
 

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Discussion Starter #3
Thanks for the reply. I got this truck 3 years ago, and followed your fuel upgrades. I run about 25 psi of boost, and let off the fuel at around 1250F when it gets up there. It pulls pretty good for an old truck. It has 59K miles, and looks good, but I dont know how cost effective a trans swap would be. The real issue is top speed, so I would like to have an OD trans, because 3000 rpms at 62ish must be hard on the motor. Also, I dont know where to find all the info about the needed pieces for a successful trans swap.
I understand I can get it to pull a load, but with hyd. brakes, stopping is a different story. I have installed an exhaust brake, but the dt360s only allow around 40psi of back pressure. Last year I tried to find exhaust springs that could handle more, but I came up short.
 

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http://thedieselgarage.com/forums/member.php?u=2457 Pipewhiner has heavier springs in hes 360, and it spins to 4k. Screaming all day at 3k isnt too good on your fuel bill, let alone the engine's longevity. With those loads, you shouldn't really change em either. A good wrecking yard will be able to put together everything you need, and personal experience tells me to go with a smaller and more personable yard.
 

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Pulling a truck without the brakes working is a no-no in a lot of jurisdictions now, the engine has a compressor mount and a trolly bar will get past most. There is also a vacuum cylinder to push the pedal that slaves to the vacuum booster. Either would work with air brakes but the slave cylinder will work hydraulic brakes. There is also an electric actuator that will work both for twice the money. Been several years since I helped a friend with a MH.

They have been hassling motor homes with a flat tow vehicle on.
 

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Straight trucks do not have an official "GCVR", typically the axle or transmission is the limiting factor because anything towed over 3500# needs brakes.
 
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Junior Member
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Have you figured your safe front axle towing weight?? You put 10000# on the sling/towbar you are prob ok. But if on a wheel lift/frame lift you may be under 50% front axle weight and this is a no no due to reduced steering stability and reduced braking.
Your question may be better answered on the Tow411 forum site.
 
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