my thing with a gv it doesnt offer that much overdrive and its so expensive. its only 22 percent. most overdrive trans are 30%. the gv itself can take all kinds of power but the trans you have in front still has to be able to hold what your putting through it. by the time you go through a non od trans then add a gv you could have built a monster od trans. a 4l60 thats capable of holding 650 hp and 650 tq can be bought for a less than 2 grand. the only thing that kills your is the adapter for a nailhead. if you want to get real crazy and run 6 gears patc offers a 6l90e stand alone controller. they are good in the 600 hp range stock and are in junk 3/4 and 1 ton trucks. just my thoughts.
It sounds like the OP's intent is to get better MPG. Assuming you get ~25% better MPG and gas goes back up to about $4/gallon, it will take a long time to pay back even $2000, unless you drive you truck a lot more than the 1500 or so miles a year I drive my 64 Wildcat. For example, if he gets 25% better MPG, that is about 10 MPG. If he drives 1500 miles per year that's a savings of only 37.5 gallons per year. At $4/gallon that is $150/year. At that rate it will take over 13 years of driving 1500 miles at 10 MPG to break even. It seems like there are better investments out there (not the stock market, though). Not trying to start a war or highjack a thread, but I always wonder if those considering overdrive strictly for increased MPG consider the payback time. There are other benifits such as better driveability and reduced engine wear.
Higher numerical gears give you snappier around town acceleration, lower numerical gears are better highway economy. It's a matter of having your cake and eat it to, or not.
I can tell you that the reason I wanted an overdrive had everything to do with better MPG and lower RPM on the highway. I never even thought about how long it would take to pay it down, not even once, nor would it have made any difference in my decision.
Yes, the GV is only .78, and truth be told, I wish it was closer to .70. The GV drops my highway RPM's by 600 RPM, and that works well enough for me. So far, I have done a best of 18 MPG going 50-55 MPH. I believe the .78 has something to do with GV's claim to exactly split the gears in most transmissions. I knew my car would see the drag strip, not a lot, but at least once a year, so the durability was important to me. I put it behind a THM400, and it cost me 1000.00 to build a fixed pitch 400 to replace my SP. The guys I have talked with who built the 2004R's have paid about 2000.00 to make that transmission last behind a stout (500 HP) BBB. Then there is the torque converter, and we know you get what you pay for in that case. Phil Sedlon made the swap back in 2005, and the grand total was 3200.00. (post #7) http://www.v8buick.com/showthread.p...R-in-a-1970-GS-A-Tutorial-Pictoral&highlight= It cost me right about 3000.00 to install the GV including a new drive shaft, but that was back in 2006. I'm not sure about the 4L60 and how stout you can make them, but I know the fastest GN guys usually run a 400 as they eventually give up trying to use the 2004R. It really depends on how you use the car. Heavy car + big power + perfect traction finds the weak link every time. A transmission with all the good stuff is going to last for a long time on the street with little abuse (no traction)
built they are limited to 600 hp or so but if you need more than that there is the 4l80e or 6l90e built idk anything that would kill it however it needs a stand alone controller. there are quite a few 800-1000hp trucks running the 80e built of course. with his nail though he could run a 60e or the 700 built up. i cant see a nail making over 400 hp or enough tq to kill it. or a stock 80e would hold the nail but it takes a little more power to turn a 80e.
The main reason I am looking into an OD is for easier highway speeds. I paid a lot to have the engine rebuilt and to have the carbs tuned to run correctly and had the SP400 rebuilt that I would hate to ruin it because of a lack of OD
As I said, that and gas mileage on long trips were my main concerns. You certainly have enough information in this thread to make a decision. The GV is your best bet if you can fit it, being you paid to have the SP rebuilt.
i agree the only other thing you could do is sell the built sp400 but idk if you would be able to come out like that.
We still don't know what gears he has in the rear. Or what kind of driving he plans on doing. Any racing or all cruise or hi way?
I went with the 200-4R. But it sure had nothing to do with mpg. I just like riding down the highway and got tired of doing it at 3000 rpm's. 2100 rpm's is much better with the OD trans.
With that set up the gear venders is your best, cheapest and easiest choice. You will still have the 3.73 for your light to light racing and you just click on the of for cruising. plus if you put the switch on the shifter you can do some gear splitting and always stay in the power band. bolts up easy all you need to do is shorten the drive shaft. i want to do this to my ride but I do have the x frame. According to the specs it would fit but I want to get my hands on one and physically put it in place b4 I spend the money. With the. Low end torque of the nail you could put different gears in the rear and get better mileage. Depend how much of the racing you plan on doing. I have a 3.42 rear in mine now but after I burn off the first set of tires I'm going with the 3.08 rear to cruise and go on some trips. in doing some research for your question I found a old hot rod web site that specifically mentioned that for a good torque engine like the nail the 3.08 was a good choice. In fact they did quarter mile runs with rear ends from 4.11 to 3.08 and all in between. The quarter mile time were better with a 4.11 but not enough unless your going to the track all the time. It was like a few tenths. And top speed was obviously better with the 3.08.
I was going to go with the 4L60E in mine and even bought the right yr preferred to start with. But, after looking at all the costs involved "bell housing, stand alone commander, tail shaft conversion for speedometer" and still only having a used tranny i am opting for the GV unit. Sure you can get an adapter plate and mess with TV cables, new cross members and hope it holds up to the torque "HP isnt the issue with the 200 or 700 as much as torque is IMO" but i would rebuild what you have and look for a used GV. I missed out on a whole truck last yr for $2500 with one and i know i could have easily sold the truck after removing it for that money. So the units are out there if you look and wait. For now i am opting to pull the 5.3 out of my wrecked GMC truck and use the 4L60E i bought for my 72 Nova so at least the 4L60E purchase isnt a complete waste.
well thats why i mentioned the 80e its super strong. your better off if you use the non electric trans like the 200 or 700 than the 60e in a these cars. the controller adds about 600 bucks. only way i would step up to electric is the 80e. you can get a race 700 that will hold 600 ft lbs. still would be fine behind nailheads. monster even has a 700 rated at 1000 ft lbs now its just under 3k price tag.
Curious how you are determining your ideal cruise rpm. What is your cruise speed now? Are you going 60 mph or 80 mph? What is your current rpms at cruise speed? Have you played with different rpms and speeds over a long enough distance to come up with a target range based on observed mileage? How is your engine built? (Don't say "rebuilt" or "bigger cam") OD seems like a good choice with 3.73's (I didn't catch tire size) I can think of a few circumstances where 2700-3200 rpms will offer better mileage. Any examples of similar built engines in similar vehicles you can go off of? Are those actually well tuned examples? It's a big check to write for a guess, maybe you already have precise info not shared to the thread o No:
Yes dyno numbers would be good to know where the HP and torque peaks, or at least what cam is in the engine and what kind of port work if any that the engine had and tire size to make an educated guess of what RPM would be the best to cruise at. Derek
I don't have any kind of dyno numbers. The engine is just a stock rebuild with a TA-25 cam with a eelco 3x2 intake on 20" wheels tires are 27.5" tall in a 1950 Chevy 3100 pickup with a rebuilt SP400. Cruise speed was 70mph at about 3000rpms.
Someone more familiar with where the peak HP and peak torque is would be better to tell you where you would want your cruise rpm than me. But I would hazard to guess that at least 500 + RPM less would be much better for that combo at that speed? I would think the G/V unit would be the way to go for sure, but not sure what the optimal rear gear would be for you? GL Derek
