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Isuzu reliability tester
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So I was talking with a tech guy from gear vendors a few weeks ago, we talked for 45 minutes about different scenarios like vehicle weight, transmission, engines, power and tq, etc.

Basicly he told me they do NOT recomend their O/D unit behind any 4 cylinder diesel and it would certainly destroy their O/D unit. He went on to say it has something to do with the harmonics made by the 4 cylinder diesel and would probably work fine with a 6 cylinder or 8 cylinder engine. The one thing I didnt like about this story is that he specificly said the testing they had done on a couple different vehicles were equipped with the 4BT and in 10,000 pound trucks. After lots of talking about my setup 3860 pound truck, 2wd, etc. he said it may be ok since there wont be much stress on the unit anyway. The one thing he couldnt tell me was if it would be any different with my isuzu engine since it runs smoother than the cummins???

Basicly he said with the low vehicle weight, smoother running engine, and non towing nature of my vehicle it would probably be fine but only time would tell.

I am going to run a gear vendors behind my 4l85e so I can have the benefit of all those gear ratios and stay in the power band as well as the .59 final gear for max mpg's on the highway.

So lets hear some discussion. I have merged some posts into this thread from another thread where LRief mentioned a camshaft was broken in the engine due to harmonics and an aftermarket balancer would help solve it.
 

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I had a Gear Vendors on my 3500. It did not make a mileage difference. In double overdrive it used the same amount of fuel with less rpm. It did come in handy once when I hauled a heavy backhoe. I used it instead of the factory o/d and got about 200 more rpm and that helped alot.
 

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it works out to be the stress at low rpms will low or no fluid flow.

They do work really well to tow and haul with though, "splitting" gears is always going to get you there faster, maybe with more maybe with less fuel..
 

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Isuzu reliability tester
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Discussion Starter #4
Now that you mention it that was brought up but then he said that anything over 20mph will be fine, he specificly said the harmonics of the 4 cylinder engine, on a 6 or 8 it will work fine.
 

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the pump in the od doesn't kick in till over 45mph by what the guy told me that I got mine from. He said in the automatic mode it gets enough pressure and shifts and he said it is very bad on them to try to get them to stay in od when lugging low rpm.
 

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that is very true that is what i meant to infer. Either way the pressure is not high enough when low rpms are present in od.
 

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I worked on a toyota T100 with a 4bt cummins and a nv4500 with a gear vendors overdrive. At 65 mph at 1300rpm he gets 47 mpg and at 75 mph at 1500rpm he gets 38mpg. Dont tell me it dont work! It worked so well he built one more. An 04 suburban 2wd 4bt with the chevy 4L65e and the gear vendors overdrive behind that. This combanation gets 38 mpg! Both these trucks I did all the wiring on so I know them inside and out
 

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I worked on a toyota T100 with a 4bt cummins and a nv4500 with a gear vendors overdrive. At 65 mph at 1300rpm he gets 47 mpg and at 75 mph at 1500rpm he gets 38mpg. Dont tell me it dont work! It worked so well he built one more. An 04 suburban 2wd 4bt with the chevy 4L65e and the gear vendors overdrive behind that. This combanation gets 38 mpg! Both these trucks I did all the wiring on so I know them inside and out
I can see the 38mpg but 47 seems a little high though. I just took a trip with my truck and was able to pull 30mpg with a a518 trans I have no od unit when taking off i keep boost below 10psi and when driving i keep it as low as possible usully around 6psi. That will be a 17mpg improvement over my setup just hard for me to believe. What is the gearing?
 

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4bt with TH400 and gear vendors

I'm considering this as I plan out what I want to do. Just a quick rundown, 66 F100 (considering the CV front end swap). This would be a cross between dd and work around the house general utility truck. I doubt I will ever tow anything bigger than a uhaul trailer also I won't be going much over stock on the engine. My concern though is the issue of low pressure line when highway cruising. So long as I can get the suspension worked out I want to be able to cruise at 75mph on the highway and get the benefit of the MPG.

On the flip side of things I don't know how the trans will handle the torque and low line pressure if I'm loping along at around 1200 RPM and making good power. Will the pressure be too low for the trans and start cooking clutches?

I'd also look into some kind of manual lock up converter so I can keep it locked most of the time since I doubt I will need much in the way of torque multiplication.


Any thoughts from the crowd on this setup.

Also if you see this Carcrafter is there any chance I can come spy your setup? I know there is basically no difference between the 66 and 67. It was over 10 years ago when I had my 66 so I'd like to take some measurements and pick your brain if you don't mind. I'm in DFW. If you enjoy a cold beverage I'd be more than happy to bring a bribe :)
 

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SM465 and GV unit

So I came across this looking for something totally different and now I am paranoid.

I am seemingly working on the never ending project where I plan to run a 4bt, SM465, and a GV unit in a K10 chevy. I am all in since I have the GV unit bolted up already.

I guess I am jsut not going to worry about it.

My thoughts though is that since the pump for the GV unit is run off a cam on the main input shaft of the unit which is directly coupled to the output shaft of the transmission it is somewhat independent of the RPM of the engine. Whether you use 20 MPG or 45MPG it is related to your out put shaft RPM which is related to your road speed not gear. So if you are worried about low RPM 5th gear, 4th plus, or double overdrive it does not matter as long as your road speed is over the 20 MPH.

What I do not like about it is the fuzziness of the 20 MPG/45MPG ... I would prefer them to just tell me the minimum RPM the output shaft shaft of the transmission should be running to reach the minimum pump pressure. I haven't directly asked them (GV) this so I cannot really complain. I can do the math to take into account the gear ratio and tire size. I could then mentally or physically (post a sticky note on the speedo) with the minimum MPH before engaging.

Anyway I have not used one yet so no first hand experience except for the installation of a used 93 GV unit behind a chevy NP205.

Anyone else have first hand experience?
 

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It's after the NP205, not between the SM465 and the NP205?

I would really like to run a GV in the NPR, but I have more than the 10K Randy mentioned.

Of course I don't really know which unit Randy was speaking to them about, I would want the one that replaces the carrier bearing on a heavy truck (like the ones pictured here http://www.gearvendors.com/ag4s.html ).
 

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Isuzu reliability tester
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Discussion Starter #12
bradntx, shoot me a PM if you want to stop by, I will have the truck finished up today ( need to finish my new weather pack connectors for the tail lights and a couple other small details).
 

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More OD info

This is an interesting thread for me. I had been shopping around for an "affordable" OD for my truck. I was looking for a used unit. That is scary by itself. I had considered the GV unit the "one" to buy, but the pricing was a little high for me. About 2 months ago I came across a unique unit on "Flee-Bay" and wound up buying it.
This unit I bought was advertised as an untested take out. It was stated in the add that it was for rebuild or parts since it could not be guaranteed. The input and output shaft rotated freely and it shifted well. When I recieved the OD I opened the inspection cover. The lube in very bad shape. I pulled the unit apart and needed to replace all the bearings and seals. That more than doubled the original price.
My OD is a Mitchell Gear Splitter. This is a unit similar to a divorced transfer case in that it is not bolted directly to the transmission. It takes a short shaft between the transmission and the OD unit. This unit is also unique in that there is no 1:1 ratio. "Low" gear is an 8% underdrive. "High" gear is an 18% overdrive. These units were rated at 20,000 gvw and were used in 1/2 ton trucks to motor homes. This unit has normal gearing just like a manual transmission not a planitary setup like the GV. Shifting is by a manual lever. With the automatic the transmission should be shifted to neutral before shifting the OD. With a manual just clutch as normal for shifting.
When I mounted the 4bt/475 turbo/hydro transmission in my short bed pickup I placed it on about the max front to rear tilt so the pan would clear the front crossmember and the transmission would clear the cab floor. When I placed the OD behind the transmission it needed to be mounted at the same angle for drive shaft universal alignment. That put the rear of the OD quite low. The extra length of the OD was leaving me with only a 24" driveshaft. My truck is lowered so the rear axle is high in the frame. This combination just DID NOT WORK. My driveshaft universal angles were way over what could be tolerated. My alignment problem was the opposite of most 4x4 guys with the big lifts.
Just before this thread started I located a used GV unit. I have not purchased it yet. I am waiting to hear more from the rest of you. I love the OD I bought and may hang on to it and completely redo the engine/trans mount in my truck. Since it is finally up and running I hate to take it apart. The short wheelbase and extra 25" of OD plus a short shaft from transmission to OD just makes the drive line too long. The idea of a 2 ft drive shaft doesn't appeal to me. My truck is a toy not a daily driver. It sees no off road use. I am hauling a 650 motorcycle on it now so it sees light loads. With no overdrive in the transmission the truck just "wants" another gear.
Next week I am leaving on a 3400 mile road trip with the truck. I am going to have to force myself to hold the speed down. I'd love to run 75 mph but won't rev the motor that hard. 2000 rpm gives me 65 mph. It is going to be a long trip. I wish I had that 5 speed manual with od now!
 

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Behind the 205

The GV unit for a 4x4 is generally behind the transfer case and requires a cutout switch when in 4wd. Since my truck is going to be a DD and mild offroad use (not rock crawling) I do not need the gear splitting in 4wd plus it will not work at that low a speed. There is a ranger unit that goes in front of the transmission but i do not think it is rated for more than 400 ft lbs.

There are a bunch setups with GV but the new stuff is way too expensive. I actually have 2 of the Laycock Demormandville (sp?) designs for a 66 Sunbeam Alpine. GV and LD in England got together and beefed up the unit. I still have not used even the sunbeam unit but my grandad said it worked great. It came out of the car sometime back for reasons unrelated to the overdrive.

This type of unit has been around for a long time and used in a number of british cars including jags and rovers.

The gasket set for a GV is fairly resonable I think it was 40 bucks and a deeper resevoir is something like 150 but I am not sure on any of the bearings etc....

Another piece of info is that older units for a Dodge or chevy with an np205 transfer case is that the have changed the adapter to eliminate the need for replcaing the transfer case rear bearing with a sealed bearing. Of coarse my had no bearing and was the old style and GV doesn't support the old adapter. I finally found a sealed bearing that was supposed to fit and was actually the input shaft bearing from a nv3500. I still had to modify the adapter a tad to make everything fit right.

I will be chacking the trans fluid in the unit from time to time to make sure the gear oil has not seeped is or vice versa.

Good luck with the used unit Beck.
 

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I've got one of the old European units too.

I have one of the old European units too. I took mine out of a Volvo if I recall. At the time I was hoping to use it as a transmission in a pulling garden tractor. That never materialized. It has been in my attic for a few years. I was planning to modify it to manually shift it instead of hydraulic pressure holding it in gear. Something along those lines anyway. Track speed in hot pulling tractors makes all the difference. I hoped to launch in direct-shift to OD-then shift back to direct if needed at the end of the pull. Launching with too tall of a gear is not possible, but an upshift after the rpm comes back up would probably work. At the end of the pull it is just a matter if you have more traction or power. If the tires never get a bite the motor will spin a big gear. If the tires bite hard a downshift would be needed.
I think I witnessed a diesel pulling truck doing something similar last week. It appeared to be a clutchless manual transmission. Lenco? I know they upshift clutchless. Do they downshift clutchless?
Wow, I got way off subject....Sorry!
 

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Isuzu reliability tester
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Discussion Starter #17
I tried looking into US gear until I noticed the price, my looking came to an abrupt halt soon after LOL.

I do hear the US gear units are top notch though.
 

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I got about 100,000 miles out of mine before it left me stranded 1200 miles from home without all the tools I needed. I tried to buy the parts to rebuild it before I left on my trip but they would only sell me a rebuilt unit. Of course once I was broke down they were happy to ship me the parts I needed to fix it. The thing that pissed me off the most is I live about 30 miles from them. Gear Vendors said mine failed because I used it to back up my trailer too much. Long story short I fixed it got home took it out and changed my gearing and am much happier without it.

I would only recommend Gear Vendors to someone that I did not like.

J
 

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I got about 100,000 miles out of mine before it left me stranded 1200 miles from home without all the tools I needed. I tried to buy the parts to rebuild it before I left on my trip but they would only sell me a rebuilt unit. Of course once I was broke down they were happy to ship me the parts I needed to fix it. The thing that pissed me off the most is I live about 30 miles from them. Gear Vendors said mine failed because I used it to back up my trailer too much. Long story short I fixed it got home took it out and changed my gearing and am much happier without it.

I would only recommend Gear Vendors to someone that I did not like.

J
I'm confused. You got 100,000 miles out of it, knew it needed rebuilt, and started a 1200 mile trip. If you suspected your transmission was bad, would you have driven it.

Their parts policy, notwithstanding, you certainly brought a good bit of your grief on yourself. I'm not crazy about that type of repair policy, but it certainly isn't uncommon in the aftermarket world to not be able to get parts directly. If you knew it needed to be rebuilt, then you shouldn't have used it. 100,000 miles seems like a reasonable service life for it, and whether or not you liked their repair policy, you are somewhat bound by it. They have no obligation to change their policy to suit you.

In short, you are entirely the one to blame for your misfortune. Not sure how you can speak negatively about the product, given your experience with it. The repair policy is another matter.
 
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