6.5 td swap to 5.3 ?s

[mcnally351]

So I have an 01 gmc c3500hd cab and chassis work truck sporting an anchor 6.5 that is giving me trouble . Doesn't start if it isn't 80* out and now is smoking horrible with some valve train noise. Truth is it could probably be fixed but I have no desire to work on this turd. I've replaced cracked heads on a 6.2 with all the hard lines, it's sucks.

Anyway, I love the truck it has a huge frame and I have towed over 5 tons with my dump trailer. I'm thinking of doing either an ls swap or a cummins.

My question is will a ls bolt right up to my 4l80e? Do I need to change the bell housing? I'm aware of most of the conversion parts because I'm swapping my k5 blazer over , but I had my harness modded on the blazer but I've heard guys doing a four wire hook up to the obs Chevys? I know my truck has a drive by wire now and electronic trans can it all be controlled by the ls harness.

Sorry lots of questions but trying to plan this repower. I do have a 6bt also that I can swap over but it's in a working truck. Thanks-

[clinebarger]

You can run the factory 4L80E, You will need a Crank spacer, Flexplate, & Crank bolts from a '01 & up 6.0L/4L80E 2500HD. Reuse the torque converter bolts that are in the truck now.

Your DBW 6.5L pedal is not compatible with LS engines. You will need to mount a LS pedal.

A 5.3L will be a absolute DOG in a 3500HD, The truck is TOO heavy!

A 7.4L or 8.1L is a way better choice.

[mcnally351]

Thank you for the reply. I know its heavy. You think it's not enough? I guess I'm not thinking enough about torque, this 6.5 was so anemic I figurered a ls swap would be a step up . I'm still thinking about swapping my first gen cummins over with the dodge trans , I was trying to keep from major metal fab but I don't want to loose the truck. I'm sure a 6.0 could keep up and be better then the 6.5 but the truck would be better off with a diesel

[mongocanfly]

I've got a 6.0 lq9 backed with a nv4500 and 4.10 gears in my 1 ton and it does fine pulling 10k gross load trailer..but the hp and torque come at a much higher rpm range than a diesel..on the dyno I'm getting 297 hp and 345 torque at rear wheels but that happens at 5 grand..ita a dog until you wind it up

[mcnally351]

Yeah that makes sense and I'm aware that it won't have a diesel low end grunt but I know how to drive an underpowered truck lol. I'm still going to give it a go. Worst case I bite the bullit and cut up my first gen dodge , just more work. Thanks for your input ! I figure a large single side gas tank would be good. Are suburban tanks in the rear or big Side tanks?

[mongocanfly]

I wouldn't call mine underpowered,, its just in a different rpm range..with my 5spd manual 1st and 2nd run out of gears quick with the 4.10s but when you hit 3rd at about 30-35mph it will put you back in the seat..it only takes about 8-10 seconds to hit 85 mph from 30mph..and pulling my 9500lb tractor it will actually pick up speed going up a pretty good hill once I downshift to 3rd..my buddys 454 1 ton auto looses speed all the way up the same hill with a smaller tractor..down side is the gas hand drops at the same rate that the speedo goes up.

[mcnally351]

That's a good point. I agree the bbc of that era is no prize. Thanks for the input I have a lot of figuring to do

[Pillow]

Here is my $.02... Having owned and towed "light" with the 6.5 and 6.0 and 5.3 LS motors.

IF your 6.5 is running right, it will be a better all around daily towing/hauling than a stock LS. And with the 6.5 you need to do some improvements over stock, period. Chip, full exhaust (I ran no mufflers), and bigger turbo (HX40 IRRC). Remote mount PMD and get rid of the vacuum controller for boost control. So for about 1500, you have a very solid base that breaths much better, better power, and runs cooler. Check out DieselPlace.com or thetruckstop.us for more info.

I would routinely take our old 1999 2500 Suburban 6.5 over the wife's 2005 Escalade (6.0) when we towed the trailer (6Kish). On the hills I would be passing gas truck everything as they couldn't make the grade (pun intended). Now the Burb was never fast fast, but much better than stock. Same with a 7.3 or old Cummins - work is needed to get them going over stock.

I loved the 6.5 because it was quiet. Really, not that bad at the rattles. Mated to the 4L80E it is a the perfect tow vehicle. And empty on the open road I could get over 20MPG in the Burb - no hope in the Escalade!

Also forget about the 5.3 doing anything heavy for towing. Just not big enough even with the stock truck cam.

Anyway I hope that ramble helps.

[mcnally351]

Thank you pillow. That's great info. Did you do any pump mods ? If any can be done. I'm not sure which way to go. Maybe I'll assess the 6.5 problems then compare the swap. Thanks for the input bro

[Pillow]

Happy to help!

The only pump mod I did was adjust the timing on it to 1.94 degrees. But you need a scanner to do it. And it really doesn't do that much. The chip is where the power comes, just like any modern vehicle.

Check out the forums I linked, loads of info there. More than I can remember for sure. But I really liked our 6.5s (I owned three over the years). But when diesel got so expensive, I went smaller for a commuter car. With the wifes newer Escalade (6.2 w 6L60E) I just couldn't justify two big family haulers. That being said, the 6 speed auto really helps when towing, especially in the lighter duty trans!

[mcnally351]

Awesome ! Thanks , I just registered to the diesel place and I'm weighing my options. I don't what the 6.5 forever but good to see some different ideas. I just need to see how bad my problems really are. I think I have a stuck valve, Lots of smoke. Thanks again

[mcnally351]

I picked up a 6.0 and a 4l80e in a donor truck. The truck is running, I'm robbing the motor and trans, harness and fuel tank.

I believe i can use the relocating plates for the motor mounts I'm not sure if the 3500hd mounting is the same as a 89-98 obs chevy trucks. I'm using the whole fuse block with ecu and harness. my friend is going to wire it up for me but I'm not sure if there is anti-thief that needs to be refreshed to run.

i will post pics soon-

[mcnally351]

[mcnally351]

[Pillow]

Lowrider status!

[mcnally351]

Yeah buddy. Lol. I got the motor and trans out. Found two broken exhaust manifold bolts. This looks like an iron head motor by the rust. Is everyone using easy outs to remove these? I know it is a common problem. I hate easy outs

[mcnally351]

[suburban99]

Originally Posted by mcnally351

Yeah buddy. Lol. I got the motor and trans out. Found two broken exhaust manifold bolts. This looks like an iron head motor by the rust. Is everyone using easy outs to remove these? I know it is a common problem. I hate easy outs

Broken exhaust bolts are very common on these motors...I had 5 on my donor motor. I welded a nut on the broken stud and took them out with a wrench. The welding helps to loosen the broken stud..

[mcnally351]

Originally Posted by suburban99

Broken exhaust bolts are very common on these motors...I had 5 on my donor motor. I welded a nut on the broken stud and took them out with a wrench. The welding helps to loosen the broken stud..

Thanks suburban99, yeah I read that. I saw a couple of guys doing that same method. I just picked up a screw extractor kit and I'm going to try one if that fails I'm going to fire up the mig

[72MARIO]

I wouldnt even bother with a screw extractor. That will take to long. ..just fir up the mig if there broke off flush weld a washer to the stud then a nut onto the washer they come right out.

[mcnally351]

Originally Posted by 72MARIO

I wouldnt even bother with a screw extractor. That will take to long. ..just fir up the mig if there broke off flush weld a washer to the stud then a nut onto the washer they come right out.

Looks like that's the way. Thanks for the heads up. I'll post how I make out. Hoping to have them all out and the old 6.5 out of the 3500hd this week