I have an 88 GMC K1500, 4x4 with a 700r4 tranny.
I was told I needed a K2500 to pull my trailer with boat.
What do I need to do to be able to pull a 4 to 5K lb. 26 foot boat.
Some one told me to buy a transmission cooler and helper springs, Is that all I need to do???

Some one told me to buy a transmission cooler and helper springs, Is that all I need to do???

Pretty much, for a boat and under loads pull it out of OD

To be legit? :laughing:

http://brochures.slosh.com/1991/th-comm38.jpg
1991 combinedweight ratings based engine, trans, and axle ratio.

Mechanically, its easy to make a 1500 into a light duty 2500. Swap in the 3/4-ton springs, 9.5" axle, make sure its the 1.25" rotors. Trans cooler and deeper gears couldn't hurt. Don't tow in OD. Make sure your trailer brakes work - I hope its a tandem-axle with brakes on all 4 wheels. Weight equalizer hitch should help too (I have no experience with them though).

Maybe ask in the tow rig forum :idea:

I have an 88 GMC K1500, 4x4 with a 700r4 tranny.
I was told I needed a K2500 to pull my trailer with boat.
What do I need to do to be able to pull a 4 to 5K lb. 26 foot boat.
Some one told me to buy a transmission cooler and helper springs, Is that all I need to do???

You don't need a 3/4 ton to pull that load. Like mentioned above, DON'T pull in OD.

But if you feel like wrenching, you can do what I did with my 1500 and put a 14 Bolt Semi-Floating 6 Lug axle out of a 1/2 ton Z-71 along with 1 ton springs out back and call it done assuming the axle is geared correctly for towing.

All you NEED is a big tranny cooler, helper springs would help, I was able to pull 4k lbs. with my K5, when it had 33s and 3.73s. I just made sure that the tranny wasnt too hot, I had a good sized cooler so it was all good. And definatly keep out of OD.

Thanks for all the info. I am getting the helper springs and a tranny cooler on Monday and deffinetly staying out of OD. I hope that works!

I don't know if it makes a diffrence but my truck has eight lug wheels. Is that an indication of bigger breaks as oposed to the six lug wheels???

if yuor truck has 8 lug wheels its probably a "heavy half ton" in which it should already have the semi floating 14 bolt refered to above as the 9.5", and double check but you might have a tranny cooler already, brakes should be good also.... just my .02

I don't know if it makes a diffrence but my truck has eight lug wheels. Is that an indication of bigger breaks as oposed to the six lug wheels???

It could mean you have an HD 3/4-ton with '1500' door tags. :D

Exactly,If it has 8lug wheels it's a HD 3/4ton. The 1/2tona and LD 3/4tons had 6lug wheels in 88'.I had one of those 88' LD 3/4tons with 6lugs.

1500- 2500 starts with changing the frame. Then you change the transmission. Putting 2500 axles under doesn't make it is a 2500 if it has the lighter duty 1500 frame and transmission.

Fix your gear ratio would be the biggest help. if you are running a 31-33 with a 700R4 or a 4L60e I would go with a 4.10 if you plan to be moving 5k regularly. If you have a TH350 then 3.73 for same range of tires.

1500- 2500 starts with changing the frame. Then you change the transmission. Putting 2500 axles under doesn't make it is a 2500 if it has the lighter duty 1500 frame and transmission.

Fix your gear ratio would be the biggest help. if you are running a 31-33 with a 700R4 or a 4L60e I would go with a 4.10 if you plan to be moving 5k regularly. If you have a TH350 then 3.73 for same range of tires.

I jut checked my GMC has 6 lugs. (my bad)
So dose that mean I can pull my load with a tranny cooler and heavy duty spring helpers?? I don't want to break anything...

dont waste time or money on the springs, your hitch is only rated for 500 tounge wieght x 5000 load wieght, if you cant put 500lbs in the back of your truck you need a new truck.

the bigger and better the cooler the better off youll be. get the 26000 with an electric fan and a tranny temp gauge.


of coarse you can always go beefy and slide a 14b ff if youre going to put a new axle in anyways.

1500- 2500 starts with changing the frame.

OBS 1500s & 2500s use the same basic frame, just a different front frame clip.

just hook up the damn thing and pull it...you're not going to break anything. 5000 pounds is weak sauce an s10 could pull 5k if it had to.

just hook up the damn thing and pull it...you're not going to break anything. 5000 pounds is weak sauce an s10 could pull 5k if it had to.

That's what I was just thinking but hadn't said it yet. In fact I have been a passenger in an S-10 towing a Caddy on a trailer.

OBS 1500s & 2500s use the same basic frame, just a different front frame clip.
Sort of Right and Wrong. Frame is taller rails on 8lug HD 3/4 and even taller on 1 ton. I "think" the LD 2500 might have the same rail on the 88 up truck but I KNOW it doesn't on 87 down.

There is a current Light duty 2500 6 lug. Even a 5 lug 2500 in the pre 86 vans. In the current line up it gets you a SF 14, higher spring rate, cooling package/tow package and a 4L60e with some beefing and revised shift points and a tow mode. the LD 2500 van still got a 10bolt. I know because I smoked two in my old 2500 work van. Van LD 2500 upgrade was all cooling package.

The HD2500 is 8 lug and depending on the motor it gets you a SF14 for the smaller motors and a FF14 for bigger motors. 4L80 for smaller motors and Allison for the bigger.

That's what I was just thinking but hadn't said it yet. In fact I have been a passenger in an S-10 towing a Caddy on a trailer.


they have the power to pull, and so does a honda, but what the real issue is is control, brakeing, and life span. he allready has a long bed so he wont have to worry about swaying as much, hes got weight so that if he romps the brakes he wont just slide into a jack knife, and he wants to keep pulling it for as long as possible, not just one trip.

That's what I was just thinking but hadn't said it yet. In fact I have been a passenger in an S-10 towing a Caddy on a trailer.

I have an 02 Z-71 and I tow my trail rig with it.
My car hauler weighs 1,500 pounds and my trail rig fully loaded with tools, gear, food and fuel weighs over 5k so I am almost pulling 7,000 pounds with a light duty pick up.
Now I am not going to tell you that my truck makes pulling this load around look easy, it does not. I am going to buy a 3/4 ton Duramax probably next year but my truck can do it. I towed my trail rig from Nevada to Ohio and the only problem I had was fuel consumption. I probably go wheelen twice a month and have no problems. I dont use helper springs. All you really need to do is put in a large tranny cooler like everyone has told you and just for good measure, you should ad a tranny temp guage too.
You definatly want to have breaks on all four wheels of your trailer and the electronic controller in the cab, it is safest that way and usually legally required too.

Thank you for all your help. This is a great forum with awsome people.

where do you put tranny cooler??? I looked at the front of my radiator and there is the hood lock attachment right down the middle leaving me 7 inches
on either side and top to bottom is 16 inches???

You can put a tranny cooler any where you want really. They make them small enough to fit behind the grill in front of your radiator. You can also put in a different radiator with a tranny cooler already built into it. They also make smaller coolers that will fit in your frame rails or any where else you would want to place it. I have seen tranny pans with cooling tubes in them and cooling fins on them, those would help to disapaite heat, they even have small in line type coolers but those are usually better for power steering pump coolers. If you were willing to spend a few extra bucks and buy a fan too, you could put the cooler any where you wanted to. You could mount it under the bed of the truck and have a fan pull air through it, you could mount it anywhere.

I know this really isn't what you asked, but you better double check those weights. I don't know of any 26' boat and trailer combinations that weigh less than 5k. Probably not less than 7k. What model boat are you planning on towing? Don't forget to add for fuel, ice, drinks, food and a lot of accessories on the boat may not be included in the "hull" weight.

That being said, we regulary tow a 7800lb rig short (<10miles) distances with a 2wd 1/2 ton on a regular basis.

You might look into a B&M shift improver. Electric gizmo that ups you line pressure in the tranny. Helps you tranny live. Around $40. Air bag would be my choice before helper springs. Adjustable for when there is no load.

i am in between the same thing you are doing..enclosed trailer, 2 dirtbikes, 2 quads, and a whole bunch of stuff..your rig can take it no problem..i got a k10 i put a hitch in and ran the wire..i just need a drop down hitch and put my ball in..but if its all tow it wouldn't hurt for deeper gears like other people said..when my dad had an avalanche he drove it from NJ to MIchigan (14 hours)the trailer hgad another 1000 pounds in it..brakeless too i think...14 feet or so..

where do you put tranny cooler??? I looked at the front of my radiator and there is the hood lock attachment right down the middle leaving me 7 inches
on either side and top to bottom is 16 inches???

I've notched out the bracket that runs infront of the radiator to fit a giant cooler, I just reinforced it using some light gauge angle and welded it up. I think the cooler I installed was 12"x24" like 26,000lb gvw. I think there is more room behind the chevy grill than the gmc, for doing stuff like that though.