[tlsmith]

Sorry for a crazy question, but here goes (I did do a quick search and found nothing). Has anybody put two transmissions in series, with the second one turned backwards, for extra gearing. Could you even run an automatic in front of a 4 speed and have four ranges of gears. I know you likely would never need that many but 4 speeds are plentiful and I already have one. I know you probably couldn't shift on the go but wondered if it might be a cheap way for more gears?
Tim

 

[IHRAcer]

Unfortunately, the torque multiplication from the first transmission would snap the input shaft on the rearmost transmission in a heartbeat.

 

[nhdiesel]

This has been done many times for many, many years. Farmers and do it yourselfers used to build vehicles to use around their property using scrap parts, and for extra gear reduction, would mate two transmissions together. Many guys have done it for trail 4x4s (and even street trucks) for extra gearing. I wouldn't mount either transmission backwards though...for extra overdrive, put both transmissions in OD and you get double overdrive. For deep reduction, put both in low. With practice, you will learn to shift both transmissions together for close ratio shifting.

For a transmission that is built just for this, do a search for "brownie box". There are 2, 3, and 4 speed aux. transmissions that mount behind the main transmission. I bought one for my Ram to go behind the Spicer 5-speed. Its a 3 speed with overdrive (and the Spicer is OD), so I get double OD and some serious reduction. Yes, there are versions small enough to put in a 3/4 or 1 ton truck. My aux. would even fit in a 1/2 ton.

Jim

 

[Grigg]

I would not try a regular transmission forwards or backwards.
If I did want an auxiliary transmission for a pickup sized truck I would be looking for a Spicer 5831 3 speed auxiliary. There are different versions with different OD ratios, including some with no OD at all, (just direct and two under drives). So don't count on every auxiliary transmission to be an OD.

Here is a picture of a slightly larger Spicer 6231A


I had a 5831 recently, and will try to post a picture of it for those interested.

Grigg

 

[toolmanoffroad]

like said befor guys are running two trannys in line, but mostly for gear reductin on the trail (have a friend who is running one now). Everything would have to be perfect to keep vibrations down when using it as an overdrive. HMMMMMMM... turning arround a devorced 205 to make an overdrive, and you could even switch it back to 1:1 by puting it in high gear :rasta: :rasta: bounce

 

[F350JOHN]

This guy put two transmissions in his F-250. Its hard to find info/pics on that setup anymore, but I do remember it in the magazines. There is a gear ratio section with some info.

http://members.aol.com/jzettel73/Index.html

 

[slorocco]

The four wheel drive crowd have been doing this for some time mainly to get additional lower gear ranges.

Here are a couple examples which just use the low range box off of an NP203 transfer case to get additional low gears.

http://www.high-impact.net/transmission_and_gear/doubler.htm

http://www.wideopenwest.com/~rballard2820/Th400-NP203-LC transfer case.htm

 

[Mikel]

Unfortunately, the torque multiplication from the first transmission would snap the input shaft on the rearmost transmission in a heartbeat.

Tire traction is ALWAYS the limiting factor. If he's going to run super-sticky 44" tires, I would say you are right. Otherwise, all that torque is going to get wasted in tire slippage long before it does any damage.

 

[gryphon68]

Another option is a Gear Vendors unit. They have Under and Overdrive units to fit most transmissions. I believe they have controls available to use them as either a manual select or automatic so that it doubles the number of gears (3 speed auto becomes a tight ratio 6 spd)

http://www.gearvendors.com/

 

[Cumminskota]

we call these machines "jitneys" we use them in the woods i've had 4 speed mounted to 4 speeds , 4 speeds mounted to 3 speed autos thats best and easiest way cause you can only run one clutch a toyota 22r with a toyota 5 speed and a chev 3 speed will haul over a cord of wood easily..mounted on a 2 ton chasis at that, so a 4 bt yall could have fun with

 

[DennyT]

Yep, I know a guy in Texas who has more than 2 in his binder You just keep the backups in direct drive until you need the reduction. You stop slam the others in whatever combo you want and crawl away literally at a snails pace.

 

[tlsmith]

Thanks

Thanks for all the input and interesting info.
Tim

 

[Mikel]

I have a 1966 Oldsmobile Toronado with a switch pitch torque converter. Depending on throttle position, the torque converter switches from high to low stall, for better acceleration or cruising rpms.

It doesn't turn my 3 speed TH425 into a 6 speed transmission. It just makes each gear higher or lower.

 

[willowbilly3]

I have seen it done too. When I lived in Alaska there was a drunken cowboy that had a one ton chevy with a th400 and a 454. He had a pickup muncie 4 speed put behind and hauled some hellaciuos loads on a 40 float trailer, never had a problem with the second tranny. I always thought in lower gears you might twist off the input since the torque would be multiplied several times from what it was designed for.
I also saw another hillbilly put a 56 Ford car overdrive 3 speed in his F-350 4x4 as a rear driveline so he could get down the highway better with those 4:56 gears. Of course he didn't used od in 4x4.

 

[Grigg]

Here are a bunch of pictures of auxiliary transmissions
http://rides.webshots.com/album/562077498ZXMnmh

Grigg

 

[IHRAcer]

Tire traction is ALWAYS the limiting factor. If he's going to run super-sticky 44" tires, I would say you are right. Otherwise, all that torque is going to get wasted in tire slippage long before it does any damage.

It also helps when you use a super HD tranny like the one in the link posted by F350JOHN, his rear tranny must be a 3053A Spicer based on the ratios that he posted.

 

[Cumminskota]

I have a 1966 Oldsmobile Toronado with a switch pitch torque converter. Depending on throttle position, the torque converter switches from high to low stall, for better acceleration or cruising rpms.

It doesn't turn my 3 speed TH425 into a 6 speed transmission. It just makes each gear higher or lower.

you mean a lock up torque convertor?

 

[Machman]

you mean a lock up torque convertor?

Nope..

What he has is a fore-runner to the lockup torque converter known as a "Switch-Pitch" or "Variable Vane". It could switch between two different torque conversion ratios..

Haven't seen one of those in years..

http://en.wikipedia.org/wiki/Super_Turbine_300

 

[nhdiesel]

Thats why when they are converted for use, there is usually a spacer plate or adapter housing between the transmissions that include a bearing for support.

I can't wait to get the 3-speed Spicer into my Ram. I wish I had an extra (and the extra room) to put one into our Durango for towing duties. The double OD would be awesome, and having extra gears would be great on big hills with a trailer.

Jim

Something to consider, An Np203 range box or GV, brownie, etc is designed to be used behind a transmission either mated or divorced, etc. These things have thier own bearings and are fully internally supported.

Non-planetary manual transmissions use the crank pilot bearing to support the input shaft from deflecting from the cluster. I know it's been done just driving an old 3 or 4 speed with a driveline, lovejoy or belt setup on the input shaft, but I really wouldn't suggest doing this for an on the road rig.

 

[91 12v]

Not sure if this is what you're after, your original post mentioned a cheap way to get more gears. Both these websites offer overdrive/underdrive components but they are a bit spendy at over 2000.00 each but practically bullit proof.
www.high-impact.net/transmission_and_gear/dualrangeoverdrive.htm
www.stak4X4.com/3speed.htm
There is also the Ranger Overdrive unit that fits between the clutch and transmission. I beleive Advance Adapters sells that unit. It's only rated for 400 ft/lbs of torque though.