The Stovebolt Site Forums The Shop Area Engine Shop Considering a gear change Patrick's...?

HI...on my 55 10 bolt differential how hard is it to install one of Patrick's differential gears. My OD unit is dead and will remain that way for several reasons so I'm looking to get a little higher third gear? Need your advice and we thank you, Steve

Patrick's and others sell a 3.55 ring & pinion kit and a seals & bearings rebuilt kit seperatly, which should really be purchased together, which can get a little pricey.

It's a little easier with 40s cars, as you can just use the 54 powerglide 3.55 rear gear section plus torque tube which fits into the original 40s rear housing and matches also the axles.

Not sure if that can also be done with the truck rear housings, where you can just go and use an existing rear gear section plus torque tube and do a direct swap, saving hundreds of $$$.

Maybe the same 54 powerglide rear and torque tube also fits the early 50s trucks rear housing and axles.
Maybe somebody knows and can enlighten us?

Many years ago I had Patricks kit installed professionally on my 52 truck and the cost has definetly paid back with just savings from gas milage.

However with my car I want to save right from the start.
I picked up my PG rear and torque tube at a local wrecking yard for only $150.
Beats the $700 for new parts and the experience required to properly replace and adjust the new ring and pinion.
Swapping the entire gear section in one piece is easier and much cheaper.

My '50 has Patrick's gears in back and I installed them myself. Not that difficult but you must take your time to properly set the lash. Now I cruise down the highway at 65 with no problem.

The way I understand it is the powerglide rear end will only fit the early 47 0n back trucks. I don,t know what the difference is though. If you have a 2nd series 55 the replacement gearset is 3.38. It is easier to install then the torque tube type 54 & earlier. I can,t say weither you can do it yourself or not. I,ve been doing em for 55 years. If you don,t get it setup right it will be noisey & short lived.

I'm with cmayna....I installed patricks kit in my torque tube '53 about a year ago. I basically spent about 2-3 hours each afternoon after work pulling things apart and re-installing, so maybe 6-8 hours total. You must pay attention to detail and follow the instructions that they will send with the kit. The lash adjustment was not difficult. I personally do not think the switch is an enormous improvement - but I feel fairly comfortable now at 60 mph.

That makes sense Wrenchbender, that 40s car and up to 47 truck rear ends are the same.
Seems like 47-55 trucks had their own bolt patterns.
Weird that 50s car rears and torque tubes fit 40s cars and trucks, but not the 47-55 trucks.
Sounds like the new 3.55 kits are the only option after all.

I think the 3.38 gears only came in open drive line rears.
With the torque tubes the highest gear ratio possible is 3.55, as far as I understand.

Going from 4.11 to 3.55 does make all the difference for longer distance driving.
I have hauled tons with the 3.55 and never look back at the 4.11 gears.
Unless you pull tree stumps regularly, you want a 3.55 rear.
The savings in gas/milage alone make the conversion worthwhile.

Who-me says it,s a 55. They all had open drive shafts but i,m not shure if the rear ends are the same on the 1st series & 2nd series.

I always thought the Advance Design 1947 2nd - 1955 1st series all had the same torque tube and 4.11 rear.

54 went to 3.90 and has a different carrier housing. In fact, to install Patrick's 3.55 gears in a 54, his instructions will tell you that an earlier carrier housing will be needed.

Had an aquaintance put in 3.40s with his 235 powered pick up and loved it. Got much better mileage without winding the engine going down the road. Still hauled well too. Not super heavy loads, but didn't haul heavy loads anyhow. Can always drop a gear if need be. I have 3.42s in my full size van and I love them. I have a 10 bolt. Henry

I made the same swap about a year ago. The 55's had a open drive line. The difference in the cars and truck are that the housing on the cars have an oval design to them while the truck pumpkin is round. The truck pumpkin is interchangable with the trucks from 55 through the mid 60's and are usually 3.90 gears.
In my application I used the 3.90 gears and an over drive transmission. This gives me a final drive in OD of 2.73 on the high way. I also have the hauling capacity with the 3.90 gears.
Gotta love it.
Tom

YEP...its a 54 truck but the PO added an engine and OD unit, open drive line, and a 10 bolt rear end from a 55-57 model truck. Patrick's is going to send out a package to me about identifying the gears.
I will need a new gasket for the dif. after counting the teeth who sells the best one and thanks for the help! T/C Steve

I use Fel-Pro myself, part #RDS 4304. Before you take the cover off, can you get the ID # that's stamped on the front of the differential carrier? It should be at the top, on the front face of the casting. From that, the gear can be determined, or at least what should be in it. If it's a '55 (2nd) axle,the code should be AF, which is a 3.90 gear.

With an open driveline and your later rear, can't you go higher than 3.55 ?
I think the open driveline rears had an optional 3.38?
Around 3 would be like a freeway gear with a 1:1 tranny and still alright with your 235 for city driving.

THANKS BILL and OTRA I will give the housing a look over and a good cleaning for a number. Perhaps as OTRA says I have what I need already. Who needs to go faster than 50 anyways....THANKS, Steve