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post #1 of 18 (permalink) Old 10-16-2010, 08:30 AM Thread Starter
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Gear Vendors Under/over?

So I've accepted the wisdom that gearing will gain me the most performance boost for the dollar. I know the 4.11's really wake the car up along with a good torque converter and a better driveshaft. However, as I am using my Thunderbird as a daily driver, I really don't want to lose mileage, particularly on the highway.

So has anyone ever used one of the gear vendor 2speed transfer cases? It's my understanding that they are a significant ratio drop, allowing you to either split each gear (a little overkill in my opinion) or just give you a second overdrive in top gear.

So, what are the pros and cons? Anyone have any experience with them? Gotten one under the car? I did a search and came up with a 7 year old thread... didn't give any real info though.

Thanks!
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post #2 of 18 (permalink) Old 10-16-2010, 09:32 AM
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moved to diffies


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post #3 of 18 (permalink) Old 10-22-2010, 09:17 PM Thread Starter
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moved to diffies
Anyone got any ideas about it?

Not really a diffie, it's a 2 speed transfer case more so, but I don't mind where it is, so I won't complain.

I mostly want to know if anyone's used one, what experience they have with them, etc? My thinking is add that and a TrackLoc 4.11, run with the straight gears, then engage the second over on the highway. Should get better overall mileage I'd guess (as long as I keep my foot out of it anyway).
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post #4 of 18 (permalink) Old 10-22-2010, 09:22 PM
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Originally Posted by Woodman View Post
Anyone got any ideas about it?

Not really a diffie, it's a 2 speed transfer case more so, but I don't mind where it is, so I won't complain.

I mostly want to know if anyone's used one, what experience they have with them, etc? My thinking is add that and a TrackLoc 4.11, run with the straight gears, then engage the second over on the highway. Should get better overall mileage I'd guess (as long as I keep my foot out of it anyway).
I would think that since the driveshafts in these cars are in a fixed location, it wouldn't be that hard to custom up a couple of driveshafts and stick your 2 speed case in the middle somewhere - maybe put two bucket seats in the back and let it stick up the center since the gas tank is under the ds.

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post #5 of 18 (permalink) Old 10-23-2010, 08:38 AM Thread Starter
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I would think that since the driveshafts in these cars are in a fixed location, it wouldn't be that hard to custom up a couple of driveshafts and stick your 2 speed case in the middle somewhere - maybe put two bucket seats in the back and let it stick up the center since the gas tank is under the ds.
I haven't actually seen one, but I understand it hangs off the tail of the transmission, and doesn't take up a ton of room since it just has a straight through or a .5 to 1 (guess) ratio option. So a shortened driveshaft would be in order. I'll do some reading up and find out what all would be needed, start saving up for it maybe. I'd really rather do a six speed manual swap, or even a T-45, but that's lots of money and fabrication and I don't have the time for that currently.

Ok, was digging around on their site...
With 4.10's, and their tailshaft OD which uses a planetary gear, you get a final drive ratio in 4th over of 2.27 to 1 which is a slight improvement over the stock in my case 3.27 to 1 rear ratio which in OD has a final drive of 2.32:1, so it seems like a best of both worlds situation... you can leave it in automatic mode and it'll split every gear giving you an 8 speed, or you can turn it off and run your regular 4.10's on the street or strip, and kick in the double over on the highway for some improved mileage.

I'll have to look into it, but it's a compact unit, goes in place of the stock tailshaft, you use a shortened driveshaft which on the thunderbird HAS to be an improvement, and you get better acceleration, and better highway mileage.... In theory anyway.

Any ideas, anyone ever used one? Anyone?

Last edited by Woodman; 10-23-2010 at 09:37 AM.
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post #6 of 18 (permalink) Old 10-23-2010, 05:48 PM
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Fitting a 2-speed OD unit on the back of the 4R70 in one of these cars would be a lot more expensive and difficult than a T45 swap. Is your only concern gas mileage? Cause 4.10s wont hurt your highway mileage that much, maybe you'll lose 2mpg tops. The real reason people don't want to do it is that the motor humming at 3K gets old pretty quick. Try this, drive around with OD off for an entire tank of gas, and see how much mileage you actually lose. No OD with 3.27s would be comparable to 4.30s with OD, so if you can live with the mileage you lose, and the rpms you're turning on the highway, then go ahead and get 4.10s and be done with it. If you don't like that, get 3.73s instead, cause they are very livable on the highway (80mph = 2600rpm) and I did'nt lose any gas mileage going from the stock 3.27s to the 3.73s.

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post #7 of 18 (permalink) Old 10-23-2010, 06:44 PM Thread Starter
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Fitting a 2-speed OD unit on the back of the 4R70 in one of these cars would be a lot more expensive and difficult than a T45 swap. Is your only concern gas mileage? Cause 4.10s wont hurt your highway mileage that much, maybe you'll lose 2mpg tops. The real reason people don't want to do it is that the motor humming at 3K gets old pretty quick. Try this, drive around with OD off for an entire tank of gas, and see how much mileage you actually lose. No OD with 3.27s would be comparable to 4.30s with OD, so if you can live with the mileage you lose, and the rpms you're turning on the highway, then go ahead and get 4.10s and be done with it. If you don't like that, get 3.73s instead, cause they are very livable on the highway (80mph = 2600rpm) and I did'nt lose any gas mileage going from the stock 3.27s to the 3.73s.
I might go with the 3.73's and a good TC then. Mileage is a concern, as well as better acceleration out of the box. The bird runs good overall, but is a bit stodgy off the line.
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post #8 of 18 (permalink) Old 10-23-2010, 09:12 PM
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These Gear Vendors things have been around for quite a long time; I'm pretty surprised they aren't more popular and being used a lot more than they are. They always almost sounded way too good to be true, but they're available. Maybe it's the price and fabrication required to get one going that's keeping them down?

If it mounts on the back of the trans, would it make the DS shorter? These cars could certainly use a shorter DS. But if it adds a bunch of weight.....yeah these cars don't need more of that either.

I remember reading up on somebody's featured car in HotRod/CarCraft (can't remember which...loooong time ago) who actually had two TH400s in his ride. One was modified to become a slave gearbox of some sort, and driven from the tailshaft of the first one.
Sounds kinda neat, but imagine carrying around the weight of an extra automatic trans. And I don't think all "6" speeds could be used effectively in that situation, doesn't seem like they'd add up to a sequential upshift pattern in automatic modes.

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post #9 of 18 (permalink) Old 10-23-2010, 09:45 PM
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Originally Posted by 94 Thunderbird XX View Post
I remember reading up on somebody's featured car in HotRod/CarCraft (can't remember which...loooong time ago) who actually had two TH400s in his ride. One was modified to become a slave gearbox of some sort, and driven from the tailshaft of the first one. ....And I don't think all "6" speeds could be used effectively in that situation, doesn't seem like they'd add up to a sequential upshift pattern in automatic modes.
Did some math for something to think about. In the case of the two TH400s (no pun intended) the stock gears are: 2.48 1.48 1.00. Assuming an ultra conservative 2.73 rear gear ratio we'd get:
2.48 x 2.48 x 2.73 = 16.79 final ratio
2.48 x 1.48 x " = 10.02
2.48 x 1.00 x " = 6.77
1.48 x 1.48 x " = 5.98
1.48 x 1.00 x " = 4.04
1.00 x 1.00 x " = 2.73
Also assuming that those two trans' shift schedules could be synced together properly in automatic mode....

For comparison, the Final Ratio of our cars with just one 4r70w and the commonly swapped-in 3.73 gears:
1st gear 2.84 x 3.73 = 10.59
OD .70 x 3.73 = 2.61

and now with some one-bad-mother-shut-yo-mouth holeshot 4.56 gears:
1st gear 2.84 x 4.56 = 12.95
OD .70 x 4.56 = 3.19

So, is the First/First ratio of the 2x TH400s a "holeshot" ratio, or is it a "rockcrawler" ratio?

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post #10 of 18 (permalink) Old 10-23-2010, 10:56 PM
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I hand one of the gear vendor under/over a couple of years ago it was for an old jag. It was not big or heavy just heavy for its size.
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post #11 of 18 (permalink) Old 10-23-2010, 11:55 PM
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Arent these things really expensive? I thought afew years ago they were $3000 to $3500.

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post #12 of 18 (permalink) Old 10-24-2010, 08:46 AM Thread Starter
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I thought I read on their website that they weigh around 40 lbs or so...
The two TH400's seems to be a bit of an overkill, where this unit is a gear splitter, so it has two ratios, a 1:1 and a .78:1 if I recall correctly. So if you were to use it with 4.10's, it's close but slightly taller than the stock ratio with a 3.27 in our cars, where if you pair it with a 3.73 you get a good drop in fourth + over.

So I'm curious... how much would a T-45 swap cost me? I prefer manuals over autos anyway, and I'd be able to keep the 3.27's and add a trac-loc vs. going with say a 3.73+trac-loc.

I'll dig around in the manual swap section for the answer to that, just thinking out loud.

Thanks for the input so far, keep it coming.
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post #13 of 18 (permalink) Old 10-24-2010, 12:54 PM
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Yes, two trannys would be total overkill IMO.

Quote:
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I hand one of the gear vendor under/over a couple of years ago it was for an old jag. It was not big or heavy just heavy for its size.
- Robert
So tell us more about it! How'd it drive? Easy to operate? Maintenance? Love it? Hate it?

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post #14 of 18 (permalink) Old 10-24-2010, 04:20 PM
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I didn't get a chance to use it. This older lady lost her husband who restored old jags. Got that and a 4 carb 12 cyl , 2 carb straight 6 , manual trans and alot of other stuff. Almost put the gear vender , manual trans and 4 carb 12 cyl in a ranger I had sitting. Ended up needing money so I sold it all.
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post #15 of 18 (permalink) Old 12-08-2010, 01:06 PM
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I know I'm a little late to this post, but I thought I would add some information.

Here’s some very good reading on the two common overdrive units available (I think US Gear has been sold and nothing is available for them anymore. ):

http://www.rverscorner.com/info/auxtrans.html

Basic gear vendor units run new $2900 - $3500, used they usually go for around $1500 - $2500

They make units that bolt to the back of transmissions via adapters (which are friggin' expensive: I think somewhere like $700 for the piece of cast aluminum) and they offer a standalone unit designed to replace a carrier bearing in a dual driveshaft setup. They are nothing more than a automatic planetary gear setup with a .78 overdrive ratio.

They have a VERY good reputation and have been around for many years.

They have a lot of really nice features that they offer specifically for the performance market: AutoDrive, AutoShift Sequencer , and the AutoLaunch. One of the problems with accelerating quickly with a gear vendor is when you shift out of one gear; you have to at the same time shift the gear vendor out of O/D to get true “gear splitting”. In the past that was virtually impossible with a race car. With the AutoShift Sequencer the electronics senses when you upshift and it automatically downshifts the gear vendor into dirddft drive. Then at a preset rpm, it automatically shifts into O/D.

One drawback is that they default to direct drive when you shut them off and won’t go into O/D until a certain speed is reached, i.e. you can’t start out in O/D.

Anyway I just thought I would share that information.

And now for my question:

How would the PCM handle the “extra set of gears”? Wouldn't it throw a code if it saw a major rpm shift, but the speed not change?

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post #16 of 18 (permalink) Old 12-08-2010, 03:16 PM
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I might go with the 3.73's and a good TC then. Mileage is a concern, as well as better acceleration out of the box. The bird runs good overall, but is a bit stodgy off the line.
Then just change the Torque Converter to a higher stall.

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post #17 of 18 (permalink) Old 12-08-2010, 04:19 PM Thread Starter
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Then just change the Torque Converter to a higher stall.

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The current plan is once I pick up my Grandma car, put a Dirty Dog TC in and get the JMod done.
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post #18 of 18 (permalink) Old 12-08-2010, 06:23 PM
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