I found a 9 inch rear end with 3.00's in it that would fit my 51 Merc good. Would it be a bad idea to run this with my Merc-o-matic and bone stock 112 hp flatty? Currently I have 3.31 dana 44. Thanks for looking.
I would guess that will be a little high . It will work, but it will be sluggish off the line, but should cruise good..... if it can get there! Lol. Bones
You will lose about 10% of your off-the-line acceleration ability. Find some 3.25 gears to put it back how it should be. Or just enjoy being able to cruise a bit faster without winding out the engine...if it'll hold it's speed, that is!
yes those 300's are a tad high. a 325 or 355 would better. My dad bought a new 59 ford car, 223 six automatic. it came factory with 355's
I wouldn't mind less rpm's at 60-70 mph but I'm concerned the air cooled transmission might not appreciate it.
Just yesterday I was checking the trans fluid and saw a little NPT plug just forward of the dipstick and I wondered if I could put a sender probe there.
I have 3.00 gears in mine, but I have a 400 Ford and a C6. Going to change back to 3.55. The RPMs are too low and doesn't move the water through the cooling system. Overheating SUCKS!
Im surprised at the cooling claim, I run 2.75 gears and 285-70-15" tyres (real tall!) on the rear and my 429 doesn't overheat even on cruise night.
I don't think cooling would be an issue. I let it idle the other day for 45 minutes when it was 90°F last weekend and the temp got up to 195° after about 30 minutes, but when I got on the road it shot down to 150°.
I just put an aluminum radiator in it and a new mechanical temp gauge so I was testing it for cooling capability.
My other question about a 9 inch, Does it have a lot of parasitic loss to run one? I realize its overkill in my car but do you think a stock flathead/auto would turn this rearend sufficiently? I don't wanna regret this. The one I'm looking at is from a 66 TBird its complete from drum to drum and it's only $150. I've also got a line on a 3.50 ring and pinion for $80 to put in.
I suspect a '66 Tbird housing will be too wide for your car, by the sound of it an 8" from a Mustang would be a more logical choice imho.
Where you located, Casey? Lots of 8" rears around here, usually from 67-68 mustangs. The 9" is definitely overkill, but if you set it up right you won't have any issues. You probably have less efficiency in the merc-o-matic than in the rear. Also something to consider, as you're finding out, is 9" centers are cheap and plentiful, so you can change the gears whenever you want. After you do it once or twice it's really less than an hour job. Going on a long trip? Put in the 2.78s. Stoplight racing? Put those 5.13s in. You get my drift.
Since your Merc-o starts out in 2nd gear it will be a little dead. I took out a Ford-o, put in a Cruis-o which start in 1st, replace the rear end with an 8.8 Explorer and 2.74's and could not be happier. My Crusi-o can be selected to start in 2nd but I now never use it that way. 1-2 is 15 mph and 2-3 is right at 30 mph. To me a 3.00 would be OK if you continually use 1st to start. There are some old trans guys that could make that happen but there a getting few and far between.. There are adapters to put in a C-4 which may be in your future. Like stated above 3.25's would be better and are reletively inexpensive.
Didn't run a distance check on these, I just know they're on your side of the lake. I've always been a parts chaser, getting a good deal on a part but blowing the "deal" on gas money. https://appleton.craigslist.org/pts/d/princeton-ford-565-narrow-5-lug-8-rear/6909888712.html https://milwaukee.craigslist.org/pts/d/ford-8-rear-axle/6909102058.html https://minneapolis.craigslist.org/hnp/pts/d/minneapolis-ford-8-inch-posi-rear-end/6895467250.html https://duluth.craigslist.org/pts/d/duluth-ford-8-mustang-rear-end/6904174196.html https://madison.craigslist.org/pts/d/jefferson-ford-9-ford-8-rear-end/6899930442.html https://desmoines.craigslist.org/pts/d/fort-dodge-ford-8-9-rear-ends/6894097918.html
I came to senses and I removed the differential carrier to get to the bottom of this. The side gears have an insane amount of play. Definitely what I was hearing. I'm bringing it to a 4x4 shop tomorrow to have them rebuild it. Basically the same as I thought last June. But since then I replaced the axel wheel bearing hoping that was it. It helped but this is the real problem. Pinion was nice and tight. There's some cast off oil above it but I'm not messing with that til I have to.
I got it out and stripped all the grease and paint of down to bare iron. Then painted with VHT engine primer and enamel. Gotta drop it off at the rebuilder so they can set the backlash for the rebuilt differential. Having them install new pinion seal too. It turn out the differential case itself has elliptical bores for the side gears. Had to buy new one. Probably from a previous owner rocking it back-and-forth D,R,D,R to get unstuck.
the 3.00 to about 3.08 was a common gear behind automatics in the later '50s and '60s. The thing to bear in mind is that the 9" Ford is a resource hawg. Most of us don't think much about it with our later engines but it may be something that you notice in your old Merc. You'll be fine once you get cruising it will probably only be noticable off the line.
The Rear end for a Merc-o-matic gears are 3.23 & My Merc. has Standard rear 3.73 so when I changed the Engine and Power Glide, I tried to Change the Tire Ratio to Help it out. When I take of with the Car it Fly's. Just my 3.5 cents Live Learn & Die a Fool
We used to swap out the gears from a standard car into our automatic cars from the '50s and 60s to get a lower gear cheap. They wind a little more on the highway but it changed our hole shot a ton.
I've always read that standard trans Mercury's with Dana 44 had a 3.91 rearend, and the Merc-o-matic's have a 3.31 My Merc-o-matic definitely has 3.31's 43÷13=3.307
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