3 GM 6.5's later now I have a Cummins

I'll start off saying I don't think I have set up my engines any different than anyone else. I used Heath diesel injectors, pcm and water injections.

First engine was the original stock engine that came in the suburban. The number eight cylinder cracked which from my understanding was a know defect.

Engine (2005 GEP long block) two was went down from cracked main webs. Engine (2008 GEP long block) went down due to broken crank, main caps and cracked main webs.

The vehicle is used in vacations which are usually in the mountains.

Still have the original 4L80E transmission and 14 bolt semi float rear end.

So after 8 months going back and forth with GM I decided to do a engine conversion with a cummins.

14 weeks later I can not be more happier in doing this. With 21mpg plus and more power than a 6.5 would dream of in comparison I say I did the right thing.

Here are my thoughts.
The 12v is not as fast (but very close) acceleration. Maybe with a little more work on setting up the shift points on the tranny to match the low torque would help.
The 12v VE engine is more quiet than the 6.5. Starts way easier than the 6.5, in any temp(engine hot or cold)
Better fuel mileage towing or empty.
Here is my set up.
12v VE Cummins, Bosch 175hp injectors (15hp over stock) Stock VE pump, 98 Cummins inter-cooler, 02 Dodge Cummins radiator, Fass fuel system, Hy35w turbo 3" down pipe to 3.5" exhaust, straight through muffler

Quote:

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Originally Posted by computer monkey

14 weeks later I can not be more happier in doing this. With 21mpg plus and more power than a 6.5 would dream of in comparison I say I did the right thing.

Here are my thoughts.
The 12v is not as fast (but very close) acceleration. Maybe with a little more work on setting up the shift points on the tranny to match the low torque would help.
The 12v VE engine is more quiet than the 6.5. Starts way easier than the 6.5, in any temp(engine hot or cold)
Better fuel mileage towing or empty.
Here is my set up.
12v VE Cummins, Bosch 175hp injectors (15hp over stock) Stock VE pump, 98 Cummins inter-cooler, 02 Dodge Cummins radiator, Fass fuel system, Hy35w turbo 3" down pipe to 3.5" exhaust, straight through muffler

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Welcome to the Cummins Club!! I would have to say the same about my conversion. I'm getting 26 mpg and that's with oversize 305 tires and a lift kit.

For better fuel economy and more power, advance the timing about 1/8". You might also consider installing a 3200 rpm spring. This is the best bang for the buck performance upgrade. Next thing is to install a Denny T Stage II Fuel Pin and turn up your injection pump. But before you do all of this, make sure you've got a pyrometer installed.

Hi EdaHall

Sorry, I guess I should have listed all I have done.

I have all of the gauges from the 6.5 build (boost, EGT and trans temp). I have installed a 3200rpm spring. I haven't set the timing on the pump yet.

I have turned the pump up to compensate for the low idle instead of turning up the idle screw.

Just about everything is stock and original except the cummins engine, intercooler and radiator.
ie A/C, tranny, transfer case, axles.

The Cummins does indeed make its power at a significantly lower rpm than the 6.2/6.5L. I'm using a manual transmission and my engine pulls very hard even from just above idle. I don't know for sure if such a thing is sold but you might check for a torque converter with a lower stall speed for your 4L80E. The converter that it has was probably matched for the 6.5L.

I did some searching and it looks like the torque converter on your 4L80E has a stall speed of roughly 1700-1900 rpm's. Max torque on our Cummins engine comes in at roughly 1600 rpm's so even with the wheels locked up, you are already above the rpm's of max torque of your engine. I also found out that there are converters with different stall speeds for your transmission. Here is one with a stall speed of 1300-1600 that better matches our engine's torque curve.

http://www.racetransmissions.com/sto...roducts_id=281

Also check these guys out.

http://www.transmissioncenter.net/4l80e.htm

http://www.partshp.com/Converters.htm

Computer monkey, does your Suburban still have the stock body and suspension lift?

Does the 5.9 clear your hood(especially up front)?

What did you use for an tranny adapter?

I'm contemplating on a 5.9 swap to my 99' Burb'.

Chase

Hi Chase,

I had to use a 2 inch body lift and a 2 inch cowl hood.

Destroke tranny adapter purchased from AutoWorld in Great Falls, Montana
PCS standalone tranny controller.

Sure looks good!

Myself, was hoping a 5.9 can fit without any body/suspension lift because my kids are small and can't quite climb in.

I had enough problems with the 4BT but it fit because it's short but a 5.9, as long as it is won't be able to get away with it.

Chase

Honestly after doing the conversion, I wouldn't even considered doing it without the body lift and raised hood. Body lift is easy to install and will make your life a lot easier.

Have you towed anything with your 4bt suburban?

With the 6bt, I have towed 9000lbs with 3.42 gears and 265/75R16 tires at 70mph. I don't know how much longer the stock (and original) transmission and 9.5in 14 bolt rearend will hold up.

I didn't tow with the 4BT, Ended up selling it before hand.

It had plenty of torque for being a 105 horse.

If your tranny goes out rebuild it. The 4l80E's are the strongest besides an Allison. When the TH400 was being designed there were no "bean counters" overlooking the engineers shoulders when designing the th400. GM added an over drive unit and made it a 4 speed. All the internals are made of steel which is why they are so strong. But, that's if you don't have other plans for a tranny conversion.

Chase

Quote:

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Originally Posted by b1jetmech

I didn't tow with the 4BT, Ended up selling it before hand.

It had plenty of torque for being a 105 horse.

If your tranny goes out rebuild it. The 4l80E's are the strongest besides an Allison. When the TH400 was being designed there were no "bean counters" overlooking the engineers shoulders when designing the th400. GM added an over drive unit and made it a 4 speed. All the internals are made of steel which is why they are so strong. But, that's if you don't have other plans for a tranny conversion.

Chase

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The 4L80E isn't all that strong. The inline engines tend to bring the weekness's out in em. There main weekness though IS the OD unit that GM added on.

I'm still using the 4L80E and will continue even if this on bites the dust. I have 182k miles on the original. I have always towed in over drive without any problems. I would think by know it is getting a little weak, but it's still hanging on.

One of the first things I did was add another tranny cooler, a shift kit and manually up the line pressure by adding a resistor. Now that I have the standalone tranny controller I do all that in the programming. I think this has contributed to it's long life in the heavy towing department.

Quote:

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Originally Posted by THEFERMANATOR

The 4L80E isn't all that strong. The inline engines tend to bring the weekness's out in em. There main weekness though IS the OD unit that GM added on.

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The only thing I hear breaking on th400 and 4l80e on high horse and torque applications is the case. Adding an aluminum pan helps out. A TH400/4L80e can be built to handle 1400 HP. that's not far behind an Allison.

Nelson Racing engines put 4l80E's behind their 1,500 plus HP twin turbo engines.

TCI builds a 6 speed version of the 4L80 that handles 850 hp right out of the box. They didn't do any mods to the rotating assembly other then adding more clutches and modifying a planet assembly for a lower ratio in first. They doubles the over drive clutch pack from 3 to 6.

Chase

Quote:

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Originally Posted by b1jetmech

The only thing I hear breaking on th400 and 4l80e on high horse and torque applications is the case. Adding an aluminum pan helps out. A TH400/4L80e can be built to handle 1400 HP. that's not far behind an Allison.

Nelson Racing engines put 4l80E's behind their 1,500 plus HP twin turbo engines.

TCI builds a 6 speed version of the 4L80 that handles 850 hp right out of the box. They didn't do any mods to the rotating assembly other then adding more clutches and modifying a planet assembly for a lower ratio in first. They doubles the over drive clutch pack from 3 to 6.

Chase

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Yes they can handle big HP, but how much torque? The ALLISON isn't rated in HP for just this reason, rather it is rated in torque input as that is what breaks em. The 4L80E has been tryed behind the DMAX and found fairly lacking with the torque input in heavier vehicles. Lightweight ones like the DURAMAX grand national, and the DURAMAX MUSTANG have proven pretty tough. But I know some guys in the vans have cursed the 4L85E behind the DURAMAX from GM.

Quote:

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Originally Posted by THEFERMANATOR

Yes they can handle big HP, but how much torque? The ALLISON isn't rated in HP for just this reason, rather it is rated in torque input as that is what breaks em. The 4L80E has been tryed behind the DMAX and found fairly lacking with the torque input in heavier vehicles. Lightweight ones like the DURAMAX grand national, and the DURAMAX MUSTANG have proven pretty tough. But I know some guys in the vans have cursed the 4L85E behind the DURAMAX from GM.

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I hear the same complaints about Allison's breaking/slipping.

Now don't get me wrong the Allison IS a stronger transmission, why? Because it's bigger. Starting with the input shaft and through out the trans body. PLUS, they are the easiest transmissions to overhaul. They come apart and go together with minimal special tools unlike the older trannies do.

My praise for the 4l80E comes from seeing them handle abuse like no other tranny can.

Take the torque converter, a torque converter shop explained the differences between the 4L80e and the Allison. they claimed the 4L80e's converter is stronger then the Allison's because the 80e's is manufactured from heavier gage material where the Allison's suffer from thinner sheetmetal causing the clutch to not seat as it should. They couldn't get enough tripple disk-billet kits to modify them quick enough! The 4L80e's factory converter weighs 80 pounds and is larger then the TH400s.

There is a 2,200 HP twin turbo gas chevelle running around with a 4L80e. Don't know if he has any problem's as of yet but with that kind of power there are other issues besides the tranny.

I'm willing to try a 4l80e in a truck puller because the internals greatly benefit from steel, where most other trannies of today use aluminum which flexes more.

As time goes on three will be more after market parts available for Allison besides Alto clutches and valve body mods.

A 4l80e can be built for anything.

Chase

6000 miles since the conversion running the 4L80E. I have 183k total miles on this transmission so far..I think I made the right choice in keeping it in the conversion.

Update:

I have a little over 12,000 miles on the install with no minor or major issues. Little things like charge air cooler hose clamp broke, had to replace the power steering pump and steering box. Extremely happy with the set up. I have been getting 17.8 mpg averaging between 65 and 75 plus mph. Tows our trailer very well with no over heating problems even in hundred plus weather.

4L80E is holding up great.

I have 191k on the body with original front end, transmission and NP246 transfer.

I did change out the 14 bolt semi float rear end yesterday. This rear end had 3:42 gears. The new rear end is a 14 full floater out of a 03 2500HD with rear disc brakes. I found the conversion axle swap was cheaper then buying the rear disc brake conversion for the 14 semi float. The new axle has 4.10 gears. I am going to disconnect the front drive shaft for now and run the 4.10's to see how I like them..I sure I'll like them better pulling the big trailer and I even bet I'll gain 1 to 3 mpg in towing over the high gear 3:42's.

Computer Monkey,
What was the cost for this conversion, did you do this yourself, where did you find the cummins engine?

I have a 95 Suburban and found out today that the block is cracked around the crankshaft, along with the heads being cracked. Not sure if I overlooked how prone these engines are to cracking but the machine shop said they are surprised to find one not cracked.......doesn't sound reliable to me.

In short, I'm thinking of doing a engine swap but not sure if the cost is better then just buying an Expedition. I need seats, for the family, and will only tow minimally. Any advice would be great. Thanks, Chris

Hi Chris,
Your correct in getting rid of the 6.5. If you are cracking the block around the crank then you are doing more than what that engine can handle.

First I would research all you can on http://www.4btswaps.com

If you decide to keep the 4L80E you won't have any problems with it as long as you keep the fluid cool and changed. 195k and still going.

Here is my thoughts on the 4L80E. From the start I added a deep dish aluminum pan to it. I also installed a shift kit to raise the line pressure (this was ten years ago). High line pressure, cool fluid and frequent oil changes I believe is the key to a strong 4L80E

Autoworld (http://autoworldmt.com/) supplied the engine mounts, transmission adapter, transmission controller, A/C and alternator brackets and pulleys along with miscellaneous stuff. Drive shafts, throttle mounts cruise control etc I got local.

I used a 94 to 02 radiator, 94 to 02 intercooler. If you do not haul large loads the 89 to 93 radiator and 92 to 93 intercooler will work. It will make the install easier. Also look into installing a 4BT with the P-pump. They also have a lot of torque, more than the 6.5 and again will make the install easier. My opinion, do not use the bread truck transmission adapter as it will cant the engine around three degrees to the passenger side. The Destroke is expensive but very solid and nice. I recommend the PCS transmission controller. You will be able to set up the transmission exactly how you want, line pressure shift points, torque converter lock up etc. I used the TMC-2000. If you do use this controller I can send you my file to upload. All you would have to do then is change you gear ratio (very easy) and tweak the shift points to your liking. It also comes with a data logger which comes in handy when setting up the controller. They didn't have the simple shift when I did my install.

I did the a two inch body lift. Help with the room when you move the trans/transfer case back. I have the 4x4. I kept the IFS front end. Many people say to do a solid axle swap.

Ok with that all said, are you going to do the work yourself and paying someone. If you are going to pay someone I say by the Ford. If your doing it your self I say then go for it.

I found the engine in a running 1992 Dodge truck for 1500. I rebuilt the engine for around 1200. Total cost to me was close to 8k including painting.

Hope this helps.

FYI

I remove the 4:10 gears and installed 3:42 in the new axle. I didn't like the lower gears. Engine was turning 2400rmp's way to high for the 6BT

Engine dyno'ed at 212hp and 520ft/lbs at the wheel with 3:42 gears.

Results:
18mph on high way, 13 to 16 in town