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Inline overdrive gearbox sources?

13K views 11 replies 9 participants last post by  Elwenil 
#1 ·
I'm wondering if anyone makes a manual gearbox that I can mount inline behind my manual trans in my truck that would give me another higher gear...or overdrive. It seems like this should be a simple thing...just a two speed gear box...push in the clutch and switch from 1:1 to overdrive.
I've looked at Gearvendors...they seem way over complicated and way too expensive for me.
Seams like some of the older larger trucks had something similar to what I'm talking about...I'm hoping to find a wrecking yard item I might be able to make work.
Basically I need better mileage out of my '84 W350 with TBI'd 416 stroker motor. It's got plenty of torque to pull higher gears, but the RPMs are way too high at freeway speeds. I could change both rear-end ratios...but that's spendy too.
Any thoughts?
 
#2 ·
mikeames said:
Any thoughts?
Unless you do find something like what you're describing (I wouldn't know about the older truck applications), the solution is pricey - gears, convert to 5spd (NV4500), Gear Vendors, or even go diesel.
 
#3 ·
He's talking about a Brownie Box, which I think were usually a lower split gear rather than an overdrive gear.  They are very hard to find these days and only fit a few transmissions.  For overdrive the cheapest route is to simply swap in a 5 speed.  Otherwise a Gearvendors or US Gear OD add on is about your only choice.
 
#5 ·
340SHORTY said:
I know years ago Borg Warner offered one, but that was 35 years ago..

where would a person look for this Laycock OD??
Sounds like your local junkyard that has a few Volvo cars in it might be a good place to start,
 
#6 ·
340SHORTY said:
I know years ago Borg Warner offered one, but that was 35 years ago..

where would a person look for this Laycock OD??
1960's - 1980's Volvo cars (some 90's too, i believe) It is commonly found behind Manual Transmissions, although i've heard it was available behind Autos too.

I once read in a magazine, that the Laycock overdrive was popular in certain drag racing circles, for a dual purpose car (street/strip) to offset low gear ratios for highway driving, while being strong enough to hold together for drag racing too.
 
#8 ·
340SHORTY said:
just talked to the rep at MO. he said the Volvo OD was only rated to about 180 HP. the adapter to put it behind my NP 435 is 900.00 ....
J-Type or P-Type?

I'm pretty sure Leon's Turbocharged 440 W350 is putting out at least 3 times that number
 
#10 ·
440 4spd Power Ram said:
There is a much cheaper way of adding a overdrive like the Gearvendors unit without the high price, I have a P-Type Laycock overdrive from a Volvo 740 Turbo mated to the rear of the NP-205 in my W-350.

The P-Type Laycock DeNormanville is the same unit Gearvendors now builds and can be added for under 1k, Maximum Overdrive sells the adapters and input shafts to use a J or P type Laycock overdrive that can be found in Volvos for cheap, the J-type is very common, Volvo used more of them than all other makes put together. The P-type is stronger but harder to come by, still cheaper than a Gearvendors unit.

Seven forward gears is nice, second over and third over are quite useful while towing, or just showing off by going through all seven gears as fast as I can {lol}

The Laycock shifts into overdrive at the flip of a switch, on power or not it does not really care though backing off the throttle is a good idea ;)

The control box the Gearvendors unit uses is not needed, only a switch and a pair of relays to lock out the overdrive in reverse and while in four wheel drive.
This is great stuff. I know alot about cars (or at least I thought I did :)) and I've never heard about this. I learned something today. Great stuff. how much length does this unit add behind a 205?
 
#12 ·
A Ranger is the same as the Brownie box I mentioned above.  They are most commonly found for B/W transmissions in my experience, but do exist for GM/Muncie and New Process, though they are ridiculously rare and impossible to find parts for.
 
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