Question: Advice on pulling a trailer with 3.73 gears - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
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6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum

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Old 07-10-2019, 10:01 AM   #1 (permalink)
ansan1200163
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Join Date: Jul 2018
Location: San Diego
Posts: 30
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I am a proud owner of a 1997 2 door Tahoe 4wd EL80e (not the EL60e) 3.73 gears. Driveline in excellent condition, tranny and rear diff both recently rebuilt with updated carrier.

In 4wd this thing has awesome pulling power but in normal 2wd mode the Tahoe is a real pig. At a stand still , say a stop sign, going up a hill, sometimes it takes a second or two for the engine/boost to overcome the incline and get the truck moving.

So I have concerns about putting a trailer and need some advise. Can I drive with trailer in 4hi on hard surfaces and on the hiway?

I don't think there is anything wrong with the truck, other then lack of stand still low end grunt she runs well. I consistently get 18-20 mpg on hiway as I have the lighter chassis being 2 door.

I also have the 3/4 ton rear end (I believe) and tow package. I would like to tow a small camper, perhaps 2,000 lb. Using it for home away from home , I am a land surveyor.

__________________
1997 2 DOOR TAHOE
FACTORY 6.5 TURBO
214,000 MILES @ 7/19/2018
Z71 TOWING AND 4X4 PACKAGE
BOUGHT AT 205,000 MILES
LITTLE TO NO ENGINE BLOW BY
KN FILTER, FACTORY INTAKE
PMD RELOCATION AND NEW INJECTION PUMP.
SOOT TRAP DELETE WITH STRAIGHT PIPE
RECENTLY REBUILT:
EL80E TRANSMISSION AND EXTERNAL COOLER.
3.73 REAR DIFFERENTIAL WITH UPDATES
ENTIRE NEW FRONT SUSPENSION

Last edited by ansan1200163; 07-10-2019 at 10:08 AM.
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Old 07-10-2019, 02:59 PM   #2 (permalink)
diesail
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Join Date: Apr 2009
Location: In, on or about the water, MD
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Well since nobody has jumped in that actually knows something about a '97 Tahoe I guess I will throw my two cents into the ring.

First, you should not be using 4WD on dry pavement unless you have a selection for "Auto 4WD", I don't know if this was an option in '97 or not.

The fact that you say it pulls hard in 4WD but not in 2WD makes me feel that that rear differential is suspect. Again, I don't know what was used in '97 but I would hazard to guess that it is a Positraction and it is worn and slipping.

Just my guess, good luck!

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Old 07-10-2019, 09:35 PM   #3 (permalink)
kmagg
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You definitely don't want to run in regular 4wd on dry pavement. Unless you want to replace your transfer case. I wonder if maybe it's building boost faster/easier in 4wd because of the extra strain put on the engine by having to turn more moving parts. Do you still have the stock vacuum operated actuator system on the turbo? These can have problems with vacuum pumps and lines/hoses connecting the components. Do you have a boost guage to see what's it's doing when taking off? Since the rear was recently rebuilt, have you been hearing any noises from it?
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200,000 miles, OPS/LP relay, new glow plugs, F style intake-EGR delete, new crank pulley, Spectra sending unit with ACDelco tank sock, new fuel & brake lines front to back, rebuilt (by me) stock turbo, new stock Bosch injectors, Heath PMD relocation with Dtech PMD, Heath fuel pump, new timing chain & crank sensor, air intake snorkel removed, new CDR, resealed engine (except head gaskets), new oil pump, Feed the Beast mod
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Old 07-11-2019, 12:50 AM   #4 (permalink)
ansan1200163
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Join Date: Jul 2018
Location: San Diego
Posts: 30
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Hey thanks for the input.

First, doubt the diff is the problem. I had it rebuilt at a axle specialist and they have checked it twice for me. (With the updated carrier and clutch packs, the shop had to add more friction modifier due to sticking). That said they have looked over everything and all is good with driveline.

As far as turbo and boost, I decided to stick with OEM system as a failsafe against over boost. I don't know what the boost is at now but other then the initial takeoff on inclines,power is good. I have changed the vacuum pump and the hard lines. I have a carb spring holding additional pressure on the wastegate and that definitely provides more power. I have the spring 'tuned' to keep tension but not cause defueling , which has only happened once when I was setting it up. I haven't plumbed in boost guage yet, but it's on the list.
So here is an example of how the Tahoe is a piggy: If I am in 2wd at a dead stop with front wheels against a 2 in curb or parking guard, I can't get enough power to jump the curb. I have to reverse few feet then jump it. In 4wd, I don't have that problem.
I just remembered, when I had the transmission rebuilt, the stall speed was changed. I think it was lowered 100 or 200 rpm. I can't remember the details but I think the guy said something about moving through the gears better with the diesel engine.
Still think it's strange this thing can yank a jet ski or boat trailer out of the water in 4wd but cant go over a small curb in 2wd.

I like the idea of this being related to the turbo/boost vs the driveline. BTW, I don't have the auto 4wd, it's 2wd, 4 lo/hi (3 buttons).

Can anyone tell me if it's safe to switch between 2/4 drive while moving?
__________________
1997 2 DOOR TAHOE
FACTORY 6.5 TURBO
214,000 MILES @ 7/19/2018
Z71 TOWING AND 4X4 PACKAGE
BOUGHT AT 205,000 MILES
LITTLE TO NO ENGINE BLOW BY
KN FILTER, FACTORY INTAKE
PMD RELOCATION AND NEW INJECTION PUMP.
SOOT TRAP DELETE WITH STRAIGHT PIPE
RECENTLY REBUILT:
EL80E TRANSMISSION AND EXTERNAL COOLER.
3.73 REAR DIFFERENTIAL WITH UPDATES
ENTIRE NEW FRONT SUSPENSION

Last edited by ansan1200163; 07-11-2019 at 01:06 AM.
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