4.8 vortec??

[cfan10]

How much trouble am I getting myself into, thinking of a 4.8 vortec swap in my 1990 suburban 5.7 tbi/700r4 (are cheaper to come by and less sought after than the 5.3 vortec)

I’ll have some spare change next month, and instead of taking a short vacation…or listening to my mom and trading the 1990 in and buying another newer suburban. I would like to do this swap, I’m mechanically savvy as far as changing parts, not so much with diagnostics.
I need everything back together by Jan 12th 2016 for school, is this actually possible?

What aftermarket motor mounts, or another vehicle motor mounts are usable. The suburban already has an in tank fuel pump.

What will I need from the donor vehicle?

As always thanks in advance for any related advice/experience. It is greatly appreciated.

[kalbert]

The 4.8 swap will be the same as the 6.0 swap, just with less ROI. There are a couple good threads here on how to go about it, and as always google is your friend.

[ElGracho]

I have a 4.8 in my 1985 C10. Did the swap this spring and I messed around and took a couple months.

You will need to change your in tank pump (Delphi EP 381 is the one you need). I used the cheap ebay swap plates. I used 2010 Camaro exhaust manifolds and flanges for them from ebay.

I did my own wiring harness, used the donor truck accessories, 1985 v8 spec radiator, dynomax exhaust kit with 02 sensors added, and the donor truck 4L60e trans. I used the 1985 trans crossmember with the 2005 silverado trans mount slid back on the frame. I had my driveshaft retubed.

I used 1991 suburban gages with an oil pressure sender added to the oil filter bypass adapter on the 4.8 and the water temp sensor turned down for 10mmx1.5 threads added to the passenger side cylinder head. The speedo and check engine light were plug and play. Your inst. cluster should match the one I used. I did have to repin the cluster plug on 85, but you should not have to do that.

I'm very happy with my results, I've been getting 21.25 mpg with my 2.73 rear gears. I've put 9000 miles on my truck since June when I started driving it regularly to work.

[snaptoo]

The subject of the economy of buying and driving the 4.8 came up with a friend that writes for several automotive magazines . He said smart guys are using the 4.8 and e bay turbo setups and making some serious HP !

[andrewmp6]

You need the engine the trans the wiring harness and ecm reflashed with out the anti theft on it.Then you have swap parts to buy like motor mounts headers of you want and other things like fuel lines it adds up fast.I would park your suburban and buy a cheap beater thats better on gas and save up my money then try a engine swap or maybe buy something different.

[RandyP]

The '90 Suburban is not a guarantee to have an electronic speedo in it. Only 1/2 of '90 models had it, at best.

[ElGracho]

EDIT:

Never mind the below. I see some trip odometer clusters were mechanical...

Originally Posted by RandyP

The '90 Suburban is not a guarantee to have an electronic speedo in it. Only 1/2 of '90 models had it, at best.

No. In 1989 maybe, but not 1990. All of the brochures specifically list trip odometer as an instrument cluster feature for all R/V series trucks in all trim levels. The trip odometer speedos are electronic.

http://brochures.slosh.com/frame.shtml?1990/gmc

[N2TRUX]

Originally Posted by cfan10

I need everything back together by Jan 12th 2016 for school, is this actually possible? .

I think you should thoroughly research the entire conversion and make sure you are capable. Its not that complicated, and has been well documented, but its still a big undertaking if you have never done it. With time restrictions added to the mix, I would not suggest it.

[tucsonjwt]

Listen to your mom - hasn't she always been right?

You might get this all done economically, but you still have an old vehicle which will always need something else fixed. Your body style is not especially in demand, so you won't add appreciably to the value of your vehicle. 2000 and up Tahoes/Suburbans/Yukons are plentiful and have all of the modern conveniences and will get 17/20 mpg - better mpg if you don't have a heavy foot and buy a 4.8/3.23 with 2WD. I have owned many of those.

[RandyP]

Originally Posted by ElGracho

EDIT:

Never mind the below. I see some trip odometer clusters were mechanical...



No. In 1989 maybe, but not 1990. All of the brochures specifically list trip odometer as an instrument cluster feature for all R/V series trucks in all trim levels. The trip odometer speedos are electronic.

http://brochures.slosh.com/frame.shtml?1990/gmc

I have a mechanical trip meter speedo in my '87 R10 that I got out of a '90 Suburban. I've parted LOTS of 89-91 suburbans, I know this little factoid. Out of the dozen or more 90 models I recall only 1 electronic speedo to be honest.

But no, trip meter speedo does not mean it is electronic. Actually my 88 K5 has a trip meter. My dad bought the K5 new, I know it's never been swapped.

[slotard]

I'd have no problem going with a 4.8 vs 5.3 or 6.0. Better mileage, makes enough power for me. Without dyno charts in front of me, I'd expect more power out of a 4.8 than a factory 350 but I could be wrong. Less torque I'm guessing. It's the same basic tranny as you have, but there are differences in control so you'll need it.

It certainly can be done in the time you have left, but it depends on your budget, your skill level, etc.

[hatzie]

Originally Posted by ElGracho

EDIT:

Never mind the below. I see some trip odometer clusters were mechanical...



No. In 1989 maybe, but not 1990. All of the brochures specifically list trip odometer as an instrument cluster feature for all R/V series trucks in all trim levels. The trip odometer speedos are electronic.

http://brochures.slosh.com/frame.shtml?1990/gmc

Not all of them were electronic. I have a trip odometer cluster with a cable speedometer.

[ElGracho]

Originally Posted by hatzie

Not all of them were electronic. I have a trip odometer cluster with a cable speedometer.

That's why I edited my post yesterday right after I posted it...

[65standard]

Do all 1991 suburban cluster have the electric speedometer?

[cfan10]

Originally Posted by RandyP

The '90 Suburban is not a guarantee to have an electronic speedo in it. Only 1/2 of '90 models had it, at best.

It actually does have electronic speedometer and I absolutely hate it. Switched twice already and still it doesn't move.

[cfan10]

Originally Posted by slotard

I'd have no problem going with a 4.8 vs 5.3 or 6.0. Better mileage, makes enough power for me. Without dyno charts in front of me, I'd expect more power out of a 4.8 than a factory 350 but I could be wrong. Less torque I'm guessing. It's the same basic tranny as you have, but there are differences in control so you'll need it.

It certainly can be done in the time you have left, but it depends on your budget, your skill level, etc.

As far as budget I'd like to stay around the $1,500 range...as far as my know how, I took a transmission out alone and I'm a girl. Thing is I have no big tools, motor hoist. I can just about change any bolted on parts, but I just don't know diagnostics.

[cfan10]

Thanks to everyone for your advice.

[andrewmp6]

You could spend 1500 alone just for the engine trans and wiring with the ecu.Add on the swap parts and maybe a new driveshaft your looking 3k easy if not more.I would spend the money on a cheap beater that is easy on gas and save up for something better or spend it on your truck later on if you want.

[Edahall]

You might also consider swapping in a 6.2L diesel into your Suburban. It would be a simpler install, less costly and the fuel economy potential would be higher than a 4.8L gas. My old 1982 Suburban would consistently pull fuel economy numbers in the upper 20's.

[bbbc10]

U can get a 5.3/4l60e combo for 500 to 800 here in dallas.....u might need to have a lil more budget around 2k to do it

[MalibuSSwagon]

Originally Posted by cfan10

As far as budget I'd like to stay around the $1,500 range...as far as my know how, I took a transmission out alone and I'm a girl. Thing is I have no big tools, motor hoist. I can just about change any bolted on parts, but I just don't know diagnostics.

Thats a tough number to stay around...I spent $1000 putting the 5.3L in my truck. And that's figuring in the engine at free since I parted out a truck to get it, plus I built my own harness so no money spent there, just time. Took me about a month and a half to get it done. Of course since you'll be staying auto subtract $250 from my figure.

My advice, you can rent hoists from tool rental shops. Get the engine and trans prepped to pull, as in pull the 2 motor mounts bolts and out ready. Also get the new engine and trans prepped and ready to go in. Rent hoist and pull old engine/trans, then put in new ones same day. Return hoist.

I recommend Car Shop CSP2370 mount plates, will place transmission in factory location so you can use the same driveshaft and crossmember. I also recommend having every single part you'll need on hand before turning a wrench.

[hatzie]

Originally Posted by cfan10

It actually does have electronic speedometer and I absolutely hate it. Switched twice already and still it doesn't move.

It's probably not the speed head.. You probably have two good heads. Don't heave em...

From the GM tech manuals...
----------------------------
The Digital Ratio Adapter Controller (DRAC) Processes inputs from the Vehicle Speed Sensor (VSS), and outputs signals to the Speedometer, Engine Control Module (ECM), Cruise Control Module (CCM) and, the Rear Wheel Anti-lock Brake Module (RWAL).

The VSS is made up of a 40-tooth rotor on the transmission output shaft and a VSS sensor coil mounted in the tail housing. As each rotor tooth nears the coil, the coil produces an AC voltage pulse. Each revolution of the rotor produces 40 AC voltage pulses. As the vehicle speed increases, the number of AC voltage pulses per second increases.

The DRAC takes the voltage pulses from the VSS and uses them to open and close four solid state output switches to ground at a rate proportional to vehicle speed.

The Speedometer switch opens and closes at the same rate as the VSS pulses. The ECM and Cruise control switches open and close at half the rate of the VSS pulses. The RWAL switch opens and closes at a rate seven times the VSS pulses.
---------------------------

Test speed head power...
Download the 1990 wiring manual. On PDF page 103 (Section A page 91) you'll find a troubleshooting table.

Test VSS signal...
Download the 1991 Emissions manual. Troubleshooting VSS is on PDF pages 122 & 123 (manual pages 3-78 & 3-79).

You can bench test these electronic speed heads with a regulated DC power supply and audio oscillator or arbitrary function generator.

I've tested tachs with an HP209a audio oscillator and a DC power supply. You should be able to test the electronic speed heads with the same setup with the Oscillator set on square wave out. I don't know the frequency to set the oscillator for specific MPH readings on the speed head but you could calculate them.