ClassicCar

raidmagicverizonnet

I have a Twin H 308 with a 3 speed manual trans with overdrive. Is there another transmission option? Are there any modern overdrive transmissions that will work in this car?

Lee ODell

kgap sells a adaptor kit to put a GM 700R overdrive automatic transmission behind the Hudson 308. I bought one but haven't installed it yet.
Lee O'Dell

Tallent R

You can change it to a Hydromatic if you are up to the task of putting in a new crossmember as well as sterring column and pedal assembly,
Roger

raidmagicverizonnet

I like that option Lee. Was the kit just to bolt the trans to the block or was there more to it. If you don't mind me asking how much was the kit?

MikeWA

If you have, say, a 4.11 rear end ratio in your car with the stick, and you change to a 700R4 (or a hydramatic, for that matter), wouldn't you also have to change rear end ratio to something around 3 or so?

J Spencer

If you have a 4.11 ratio you will have a 2.88 ratio in overdrive or with a with a automatic overdrive as both are 30% reduction. A 3.90 ratio would be 2.73 and a 3.58 (51 automatic) would be 2.51. Original overdrive ratio of 4.59 makes it a 3.22.

To figure RPM at speed the formula is Axle ratio X MPH X 3.36 divided by outside tire diameter. EXAMPLE 2.88 ratio x 65MPH x 3.36 divided by 28" tire diameter = about 2250 RPM's. Hope this helps.

Jim Spencer
WNY/Ontario chapter

Lee ODell

raidmagicverizonnet 4:31AM Flag
Posts: 22Hitchhiker
I like that option Lee. Was the kit just to bolt the trans to the block or was there more to it. If you don't mind me asking how much was the kit?

The kit comes with adaptor, gear reduction starter and instructions. I got the kit some time ago, waiting for the hydro to wear out before using it. Do not remember the cost. I can make a copy of the instructions and send you a copy if you like. You can PM your address to me.

Lee O'Dell

DocHornet

I can only wonder... why? Unless you are missing a left leg, why would you want to revert to the anachronistic Hydramatic, or even try to retrofit a more "modern" auto tranny?

These 3-speed overdrives are a joy to drive, essentially a 4-speed box, and they are virtually bulletproof. Even a rebuild of the transmission is simple and inexpensive. I did my own (no prior experience) for a total parts cost of about $150.

Trust me, you WILL spend close to two grand to convert over to an automatic, and that's if you do all the work yourself (lots of fabricating for the tranny mount for one thing, as noted above)
Caveat emptor

Tallent R

The big problem if you want to change to an automatic as Doc aludes to is the crossmeber is welded in. This is fine for the standard shift but to get an automatic in the crossmember needs to be removeable,
Roger

raidmagicverizonnet

I'm not convinced I want to do this I am just researching my options. No way I get into this for 2 grand. I already have an overdrive trans and I can build my own crossmember I built all that on the T bucket I sold to buy this car.
I'm going to spend some time cruising with this set up as is before I make any decision on what I want to do long term

Tallent R

There is nothing wrong with the original overdrive unit as was stated they work well and are durable. And frankly are prety neat to drive ,making a shift by letting off the gas very much like an automatic transmission would.
Roger

brumac

Why not change your rear axle ratio. It is a DANA 44 and there is a variety of ratios available. I am changing to a 2.72 in my 308 powered 54 which will give me about 2000 rpm at 60 mph. A lot less expensive than an adapter and new trans. It will also make the old Hydra-matic easier to drive in traffic. The Hydra-matics are near bullet proof if properly maintained and is what B & M Transmission built their reputation on, back in the day.

Bruce

hudsonguy

Also, you have to consider the starter and flywheel differences when making a switch from manual OD to automatic. I would concur you could easily spend a couple grand to do this.

I've got the single lever OD mated with a 4.11 axle, and I love it. Having said that, I do want to upgrade my differential to a Dana 44 from a Hornet with a 3.73 gear installed. I hope I have the funds to do this soon, so I can save some gas money going to San Mateo next summer.

dougson

I had my Dana 44 rebuilt and fitted with 3.91:1 gearset. I was told that 3.91 was as low numerically I could get without changing out the entire carrier. Total rebuild plus Richmond 3.91 gears was $1250. I've posted here before about my 5 speed conversion using a WILKAP adapter. I love it but would not recommend the conversion to the light of heart! Very expensive and very complicated.

faustmb

I have always liked driving stick, and I do enjoy driving column shift. However, when driving in heavy traffic my left foot enjoys the break. I also had a right wrist injury from mountain biking about 10 years ago which has never healed right and takes a lot of fun out of stick shift.

If I ever pursue a daily driver Hudson again, I will likely use a modern automatic transmission. My truck had one and I didn't miss shifting one bit, no pun intended.

46HudsonPU

Related question - What is the final drive gear ratio on a non-od two-lever Hudson tran?

Lee ODell

Hi Rick

The final drive gear ratio will be whatever the rear end gear ratio is. The 3rd gear in non overdrive trans is 1 to 1.

Lee O'Dell

46HudsonPU

Thanks Lee - that makes it pretty simple. Looks like optimal gears for the rear to be 3.08 - 3.27 (3 speed, non-OD) (2200-2400 RPM for 60 MPH - depending on the size of the tires).

MikeWA

Rick- Gearing that low will give a good cruising speed, but make it a real dog off the line. Tradeoffs, I guess. I had a '59 Ford with automatic, and the transmission died, so I put in a stick. Left the rear-end gearing as was, probably about 3.10 to 1. Had to slip the clutch some from a standing start, but good cruising speed.

46HudsonPU

@MikeWA - The rearend I have acquired is a 3.73. It is my intent to put that in, and see how it does.

Depending on how that works (and my level of satisfaction with the highway performance), I may change to 3.55, 3.27 or 3.08 gearing.

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