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Old 11-24-2017, 11:05 PM   #57
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Originally Posted by Keyair View Post
The 4L80E series GM Transmissions, are 4 speed, OD transmissions with a lockup convertor. They bolt right onto the 454, or LS and are the successor to the TH400, and TH475 transmissions.

The E dictates, they need a electronic controller... either stand alone, or linked to the TBI, or EFI on the engine.



The 4L80E is rated at 440ftlb of torque and 18,000lb GVRW

The 4L85E is rated at 460ftlb of torque and also 18,000 GVRW.



However, it is my understanding that the 85 has straight cut sun gears... like the TH475.



https://en.wikipedia.org/wiki/GM_4L80-E_transmission


Last time I checked, I think the controllers were about a thousand bucks. I haven’t ever tried one myself though.

A built up 700 R4 might work. They were pretty strong in their own right, but then it might just be an expensive failure.
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Old 11-25-2017, 07:08 AM   #58
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An alternative to the standalone controller would be to install a GM TBI controller, add the appropriate sensors needed by the controller and then have a "Tuner" (person that modifies the program inside the ECM) to just control the transmission.

I think the only sensor you would need would be the Throttle Position sensor although you might need a Manifold Absolute Pressure sensor as well. The Tuner would block or disable any code not associated with controlling the transmission.

If I ever decided to get rid of my TBI setup that's what I would do in order to keep the 4L80e. The cost for this type of control would definitely be less than $1000.

Brad
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Old 11-25-2017, 08:50 AM   #59
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this is a reply to my response.....my GV OD unit is not working now....a little over 2 yrs and 24k miles. NOT happy.
When your GV was working, behind the Isuzu TD, what type of RPMs were you seeing at 60-62mph?

Mike
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Old 11-25-2017, 11:02 AM   #60
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I think the RPM's with the GV engaged at around 60 is 2300. (+ or -) Without the GV, it is around 2800 +
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Old 11-25-2017, 12:39 PM   #61
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Same same without the GV and Allison at545.
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Old 11-25-2017, 11:12 PM   #62
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I think the RPM's with the GV engaged at around 60 is 2300. (+ or -) Without the GV, it is around 2800 +
Which as Mike pointed out, 2800 rpm's at 60 is what his Allison and my 475 run.

I think the guys at GV maybe onto something. What is happening, is your engine in GV overdrive is putting a lot more fuel into the cylinder at a lower rpm to maintain that speed; so yes, your rpms are down, but the combustion of that much more diesel would give more of a driveline impulse, with a larger interval between impulses; versus an engine turning 500 rpms faster, which would have less of an impulse, but more frequently.
Think an air ratchet tool (without GV overdrive) versus air impact tool (with GV overdrive). Both use the same amount of air in operation to accomplish the same work but the air ratchet is smoother turning at a higher rpm as its firing impulses are more frequent, than the air impact turning at a lower rpm, which hammers.

I maybe wrong, but is it a possibility?

Cheers
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Old 11-25-2017, 11:22 PM   #63
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Gear Vendors Overdrive

Quote:
Originally Posted by Isuzusweet View Post
Which as Mike pointed out, 2800 rpm's at 60 is what his Allison and my 475 run.



I think the guys at GV maybe onto something. What is happening, is your engine in GV overdrive is putting a lot more fuel into the cylinder at a lower rpm to maintain that speed; so yes, your rpms are down, but the combustion of that much more diesel would give more of a driveline impulse, with a larger interval between impulses; versus an engine turning 500 rpms faster, which would have less of an impulse, but more frequently.

Think an air ratchet tool (without GV overdrive) versus air impact tool (with GV overdrive). Both use the same amount of air in operation to accomplish the same work but the air ratchet is smoother turning at a higher rpm as its firing impulses are more frequent, than the air impact turning at a lower rpm, which hammers.



I maybe wrong, but is it a possibility?



Cheers

Tony


Additionally, the GV when in overdrive is under a greater torque load at a lower RPM vs. delivering the same power to the ground in direct drive at a higher RPM. I want to guess that they get hot on long stretches in OD in a motorhome.

These were designed for much smaller vehicles.

Engine induced harmonic vibrations hitting the gears and bearings under sustained torque, making the oil hotter and less effective, it all cascades into failure....
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Old 11-26-2017, 03:08 AM   #64
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Somehow I think we may be getting carried away here. Gear Vendors sells these units for GVW of 25000 lbs. and for all Ford, Chevy and Dodge diesels. They have units in dragsters and land speed record cars. Some sales guy trying to make excuses for a customers failed unit wants to blame out little Isuzu, which happens to be about the lowest powered engine in their applications catalog, I'm sorry but I don't believe it.

The guy with the failed unit admits he was unaware of not using od on downgrades and the proper oil and change intervals may be contributing issues. Furthermore without seeing the oil from the unit and disassembling the unit how can we diagnose the problem with no information.

Remember our TH400's have planetary gears and clutches and bands and our little Isuzu's haven't destroyed them with their little diesel impulse. I may be the only one but I've put too many happy miles on mine to accept the word of somebody on the spot trying to make excuses especially while he is contradicting everything on his company's literature. How many Airstreams with Isuzu's are running GV's that failed for this guy to make such a statement. I'm just not buying it.
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Old 11-26-2017, 07:58 AM   #65
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Okay then; it's not a possibility. I'm good with that.

Cheers
Tony

PS I think oil changes every 1500 miles is a little too much don't you think Dan?
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Old 11-26-2017, 08:46 AM   #66
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Just my thoughts...


The known weakness for the GV is engine braking while engaged. Shortened life of the clutch is well documented when the OD is not disengaged while coasting downhill.

I have not made the leap, yet, but have continued to research.

The GV overdrive is not an install and forget device. It takes some care and feeding. Proper use and maintenance, as with any machine.


Regards,


JD
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Old 11-26-2017, 05:23 PM   #67
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I just had a thought....I've never changed the oil in my U.S gear underdrive unit; oh what I have as it's plumbed in with my engine oil.

Cheers
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Old 11-26-2017, 05:59 PM   #68
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Quote:
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Just my thoughts...


The known weakness for the GV is engine braking while engaged. Shortened life of the clutch is well documented when the OD is not disengaged while coasting downhill.

I have not made the leap, yet, but have continued to research.

The GV overdrive is not an install and forget device. It takes some care and feeding. Proper use and maintenance, as with any machine.


Regards,


JD
I believe the owners manual tells you not to use overdrive going down hill. As you say proper use and maintenance makes it work well.
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Old 11-27-2017, 02:25 AM   #69
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I believe the owners manual tells you not to use overdrive going down hill. As you say proper use and maintenance makes it work well.
Agreed Dan, and as I wrote in the other GV thread (why do we seem to have to have two or three threads started on every subject????) I was more surprised after having Bella's fitted that there was a need for the high level of maintenance....GV never told me before hand, the guy who installed it (and transmission specialist) never told me, I had done two trips and covered around 1000miles before siting to read the manual (and who reads a manual normally) only to find the GV has the highest maintenance requirement of any system on Bella.

In a little 20ft with a 350 small block they work great, but I am conscious of having introduced another thing to worry about.
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Old 11-27-2017, 08:57 AM   #70
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After all this talk on gv I'm shying away. For me I need something bulletproof & idiotproof. Oil changes every 20 000 miles. The Isuzu is a workhorse, maybe I'll just have to accept it spinning at 3200rpm when I drive. I can always work on the sound proofing in the csb( I already drive with a king size heavy heavy quilt over the doghouse it. Works surprisingly amazing.)
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