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My 49 GMC has the closed drive-line and differential with the stock 4.11:1 gear ratio.
Does anyone have experience with converting diff to 3.55:1 with a kit like that available from Patrick's? Is it worth doing since my truck is almost 100% stock?

G'day mate,

Fred Stevens has a great write up on this in the Tech Tips section. I put the 3.55 kit in my 41 at the end of last year. I thought long and hard about whether to do that or go to an open driveline. Whether its worth it really depends on how you use the truck. The 41 is a daily driver for me and I do a few longer trips. There is a noticeable drop in revs. With 31 inch tall tyres the truck would cruise happily at 50mph. Now it cruises really well at 60 - 65 although I usually sit at just under 60. If you do decide to put in the 3.55 get the overhaul kit as well and replace all the bearings etc. If you have any more questions, fire away. Welcome to the bolt.

Bob

I did the Patrick's upgrade BECAUSE my truck is almost 100% stock AND I wanted a daily driver. We've put about 850 miles on it since changing to the 3.55:1 gears and life is good.

Like mozzie says, if you go this route, get the overhaul kit along with the ring and pinion kit.

Thank you both. Did either of you do the work yourself?

Yup, wasn't too bad a job, just make sure you can lay your hands on the special tools, dial indicator, pin spanners, etc.

I talked to the guy that did my engine rebuild this past week. We got to talking about this job and he can and has done it for $3-400. Does this sound reasonable?

I think that $300 - $400 is VERY reasonable for the job involved. Bear in mind that $60 - $75 per hour seems to be a going rate for mechanical work on autos, trucks, motorcycles, etc.

I had maybe 20 hours of my time involved, but a lot of that time was spent cleaning parts, reading manuals, searching for or making tools and so forth.

I think its a job you could do yourself. It is a messy one, but you can do it yourself. It just means you'll need to buy a few tools.

I was at harbor freight yesterday and noticed they have pin spanners ($5) dial indicators and magnetic bases (about $20 for the set), feeler guages and most of the other tools you need to rebuild these rear ends.

Speedway motors also has a rear end rebuild tool kit.

As far as the install kit goes- It is definately a good idea to replace the bearings etc... I would check with some of the standard parts houses, especially NAPA, to see if the price they can sell you the individual parts compares to Patrick's. Having a list of the parts you need is very helpful. In the more modern 10/12 bolts there are two axel seals, a housing seal, a cover gasket, three bearings, a crush sleeve and a shim kit. Maybe someone can chime in with the parts for this project...

Randy's Ring and Pinion is also an excellent source - check with them for any specialized
tools required. Good Luck!

'67 Chevy 1/2 Ton 283 350 Auto.