2nd Gen Non-Engine/Transmission Double overdrive Question???

[Mundgyver]

Good morning to the Forum



I'm contemplating the idea of putting in a gear-vendor overdrive in to the truck. The question I have is for anybody with one of these units installed. In the realistic world, what did you see in the way of a gain in fuel mileage from before install and after install

The next question has to do with the Speedometer. Are any modification necessary in the way of compensating? Are there any areas of concern with cruise control?

I'm looking at putting this on a 2500 SWB H. O. with 6 speed. I currently get 22. 4 mpg on long trips. I want to top 25 mpg if I can.





Thanks for taking time to look at this Mundgyver

 

[B.G. Smith]

Opinion

I don't have an O/D unit but from past experience I would say that with the 3:54 rear you wont be able to gain any fuel efficiency unles you drive extremely fast (85+). First, the engine is only turning about 2k at 70 mph and seems to lug at and RPM much lower than that. Second, there will be some mechanical energy loss through the gearing of the O/D unit which will have to be overcome to break even. JMHO bg

 

[sheldon]

The wind resistance will do you in anyway. Besides, 22. 4 is very good for a 24v. Mine runs about 21. 5 unloaded and 12. 5 when grossed out in excess of 16,000 pounds.

 

[GLASMITHS]

What sheldon and B.G. said

I have a GV (see sig). I ordered the truck equipped for the GV and for towing. It works great with the 4. 10 - I would not put it on a 3. 54, unless, you intend to run in 4th and GV.



I have used both running empty at 75, the rpm about 2200. But the fuel mileage is no different than inDodge o/d at 70. When I tow I stay in 3rd and use the GV for o/d. There is one drawback that is not very clear in the instructions and the installer didn't inform me correctly. YOU CANNOT USE THE GV WITH E-BRAKE. Ask me, I just replaced mine. It will cause 40-50% more wear. Mine lasted about 55K. Should have lasted 100Kplus. If you are keeping the TCC locked up for braking, you have to come out of GV, period.



If you want it for extra mileage, it will never have a payback. How long will it take you to save $3200. 00. With my truck, it takes a serious incline to make me downshift to 3rd only. It is more driveability than miserability

 

[Mundgyver]

All good points to ponder. Thanks for the replys.

 

[Evan A. Beck]

Diesels + Gear Vendor = problems. I have seen so many GV units fail because of upreated engines. I would never buy one, becuase the failure rate with a diesel is so high. If you have a 2WD, and your GV fails, better call a tow truck. With 4WD you'll be able to limp home with the front axle. GV units are expensive to say the least. Why do you want double overdrive, anyways? Most of the guys that have a GV installed on their trucks think that loweing engine RPM is a good thing. That's just not true at all... I hate to sound negative, but save your money. You'll just end up wishing you had never installed the thing.



25 mpg? Adding a GV will not give you another 2. 6 mpg. 22. 4 mpg is really good, higher than most 24V trucks. Lowing your RPM will not really give you any gain. The load on the engine will actually go up because of more load on the drivetrain in double OD, so you won't see much gain in MPG.



I'm not sure what you have for power on your truck, but getting some balanced injectors and an EZ box will give you a slight MPG gain.

 

[GLASMITHS]

GEAR VENDORS OVERDRIVE AND DIESELS

The failure rate of the GV has no relationship to power. It is rated for 30,000 lb. The failure rate, imho, is related to hotrodding with HP, and abuse while towing(my problem) (un-knowningly ):-{} :-{}



If your rpms drop below 1800 on the 24V, your mileage goes down with it.



When and if this one goes out, I will spend the $600. 00 for a replacement. Its worth it if you have a 4 . 1 0 . and a 16. k fifth wheel trailer. If my truck was 3. 54, 6 speed, as Mr. Beck said, a set of 275 injectors and an EZ will be much better and 1/3 the cost. or less.

 

[Mopar Man]

GV and OD

I have a 5 speed with 3. 54 rears and a GV OD. I agree, 5 speed plus the GV is really overgeared --I can watch the EGT climb so I don't use it except on long , but not steep, downhills. For towing, I use 4th plus the GV which I find perfect, and a quick button push and fast clutch/declutch and you are pulling in 4th direct. . (The difference between 4 + GV and 5 direct is about + 200 RPM's) I also use 3rd, then 3 +GV, then 4 direct, then 4+GV I have one location where I pull on to a 65mph road at a uphill and 3+GV is great when pulling a trailer. I really bought my GV to get the half gears for 3rd and 4th. I love it.

 

[GLASMITHS]

Driveability

As Mopar Man explained-excellent example.



Another one: In the past, before the EZ and DTT, I could not pull the mountains in WV (I-64) in 3rd direct. So I downshift to 2nd and GV. If no GV have to slow down to 35 and downshift to 2nd; and let all the Phords pass With the GV and 2nd you can maintain 48-50 and pass most of them. In the spring trip I never had to go below 3rd direct-55mph Pass all the OTRs and Phords. Never saw a Chebby. Maybe they are afraid to go that way:-{}

 

[Paul]

Do not expect to gain any mpg. If you do it will never pay for the unit. The reason I installed one is for the extra gears and to OD my OD on the highway. With the 12 valve and 4:10 gears it works great.

 

[Doubleclutch]

Us poor 5 speed 12v guys are the ones who can use the GV most. The 6 speed guys have the gear splits we need in the 5. Again, as has been previously mentioned, the 4th over will keep the 5th gear nut firmly attached. I need greater than 75 mph to consider fifth over with my 3. 54 and 33" tires. Not to conflict with Evan, GV has been making improvments to their unit, and have an industrial (no moving parts) heat exchanger for the upper crust fellows who tow with enhanced fueling. These upgrades were what made the unit acceptable for me. . up to the enhanced fueling part. I received several warnings about the E-brake addition, and have a ground cut/out switch to keep the brake from working in OD. (easy add)

Greg

 

[GLASMITHS]

DoubleClutch

Who may I ask, are "the upper crust fellows"?

 

[Evan A. Beck]

I have found the GV to hold up best in the gasoline applications, such as Class A and C motorhomes. They are usually powered by a 454 or 460, and of course the 6. 8L V10. We have had virtually no GV failures in this type of application. I attribute it to the power band of the engine, and the way the GV is used. I would say that two out of every three we have installed on diesel pickups have failed within 6 months. Interestingly, they fail less frequently on AT equipped trucks. Perhaps this is because the shifting of the GV is not being done by the driver... Hmmm... Also, double OD that kills the GV, not the split shifts below OD.



In fact, we recommend against putting a GV on a Cummins or PSD because they just tear it up. Literally! I have seen them with busted gears, etc... The GV is no match for a 350+ HP Cummins... It seems to do ok behind an IDI Ford with a C6 3-speed...



I have very little experience with the US Gear product, but I am curious to how it performs compared to the GV. All I know is that it goes in between the T-case on a 4WD, and uses a different (non-hydraulic) shifting mechanism. Anyone have any experience with it?

 

[GLASMITHS]

HUH

A GV does the shifting on an AT?



I always shift mine manuel. The first shift at 18mph in 1st must be in manuel or it won't shift till 45; and you can't use it to split gears in auto mode. Maybe mine is an old model

 

[Shooter]

Direct/ GV od is 2200 rpm @75mph. Can't cruse any sweeter than that. Mine has an input that locks out od, shifts to direct when E brake is engaged, also 4 wheel drive. I grenaded one in 12k miles, The Power Shop did the R&R. The xchange unit shifts smooth, The original always banged into and out of od.



I only use mine while towing and only in direct as the truck will pull ok in 1,2 and 3rd, just not fast enough. I do not tow in Dodge OD.

Would I do it again ? I would get a 6 speed w/ 4:10's and get a US Gear. I have developed an alergy to automatics be they 4 speeds or 2 speeds.

 

[Evan A. Beck]

Re: HUH

Originally posted by GLASMITHS

A GV does the shifting on an AT?

The GV has two modes, manual and automatic.

 

[E-9]

US Gear

I have had a US Gear unit in my truck for 70,000 miles now with no problems. I installed it for the ability to split gears while towing, not the overdrive. Also, if fifth gear fails, I still can run fourth over, which is only slightly lower than fifth direct. I can tow in double overdrive and do when the conditions are right, but most of the time is in fifth gear direct.

 

[Doubleclutch]

Upper crust fellows

Who may I ask, are "the upper crust fellows"? Glasmiths, those are the guys with twice as much power as me. Evan's experience makes me pretty nervous about the unit in my truck. I've talked with the GV Boss and have some assurances that keep me from pulling the thing off. I really like my OD and would miss it a lot.

Evan- Rick at GV mentioned significant fixes for the older units: 1) Older products (2000 and older had a pump cam on the input shaft held by

a woodruff key - the keyway can lead to failure of the input shaft ) newer

products all have ball type driven pump cams and cannot be broken (at least

not yet and we have them behind 1500 hp in racing applications).



If you have an older GV you can replace this input shaft with the later

style very easily, it just slides out

of the front of the overdrive.



2) Nitrite Annulus have been standard on our cummins product for 3 years.

Serial number ends with an E on all 99 -2001 units and all 2002's have

this process. The nitrite (actually a nitrate process) greatly extends the

ability to hold up to heavy use when towing. To upgrade both the input

shaft and annulus would be most cost effectively done as a factory reman.



3) If you are towing heavy with a pumped up motor (upper crust- Glasmiths) you should use our

commercial cooler - which is easily bolted on to the overdrive and provides

16 row dual manifold quality cooling, without motors pumps, fans, or any

external plumbing.

This is a copy of the letter Rick was kind enough to send to me. I've deleted prices per the TDR forum guidlines. I have no affiliations with Gear Vendors, and am only a customer. I asked because I value the experiences guys like Evan have shared with us. Greg

 

[Evan A. Beck]

Re: Upper crust fellows

Originally posted by Doubleclutch

Rick at GV mentioned significant fixes for the older units: 1) Older products (2000 and older had a pump cam on the input shaft held by

a woodruff key - the keyway can lead to failure of the input shaft ) newer

products all have ball type driven pump cams and cannot be broken (at least

not yet and we have them behind 1500 hp in racing applications).

I have seen these get completely sheared off, leaving flakes on the pan. Serious carnage! IMO, the cam driven pump is ok, but the oil capacity is just too small. I think they would have fewer problems with a larger oil reservoir and better filtration.



The US Gear unit just plain looks more stout than the GV. I like the way it mounts to the transmission better than the GV does. Plus, the GV uses small studs & nuts to hold it to the tailshaft of the transmission. Looks like a weak link to me, but I haven;t seen any problems with cracking, etc.