need some hamb help. i have a caddy 500 to th400 ****** in my 49 hudson. i put an s10 rear end behind it. my problem is 2 things. 1st, it shifts very early at low rpm, and will be in third at about 15-20mph. 2nd problem, i get up to about 55rpm and am redlining. cant even get on the damn freeway with this thing yet. ive never had a problem like this in any other car before, so i'm stumped. any advice or knowledge in this area would be appreciated!
makes no sense...55RPM is redline?.... tire size? rearend ratio? all this can be figured out on paper before building your car... we need MORE info.....
Or your transmission is not functioning properly....sounds like the vac*** line is not hooked up for the modulator... I also agree the gearing on the S-10 rear might be out of whack some, but not the entire problem unless you put some way undersized tires on it...
x2 on the vac hose. I had a problem once with the vacuum line to the modulator on a TH400 in a Jeep: Reved really high and shifted 1-2 with a really really harsh bang. Replaced the cracked vacuum hose to the modulator and it was ok again.
Damn, a s10 rear behind a caddy 500.... I pretty sure the s10 had 3.80's ?? for the 4.3 and 4.11 for the small v6's and the 4 bangers..... I'm guessing you might need around 3.00's depending on your tire size
The S 10 had an overdrive and was probably a T5 . If the vacuume was not hoked up to the module, it would hang in 1st till very high RPM and then hit 2nd real hard. It would have nothing to do with high RPM on the freeway. This is gears gears gears. Nothing more, nothing less. You need to change gears. With the 500 cid caddy, you could even stand for gears in the 2 series like 2.56s. These were real common in the 70s in the later Trans Ams . The whole rear ends go real cheap and are all posi's in the T.A's It might be worth a look to see iff they would be the same width to fit the Hudson.
Can you hear it shifting into 3rd gear? Shift points are controlled by vacuum- early shifting sounds like low vacuum or malfunctioning modulator. Also- do you have a kickdown mech hooked up? Redlining @ 55 mph is like being in 2nd gear. Which means that it is probably not holding 3rd gear- again, a transmission/valve body issue.
With regards to a 3.80 rear gear-- I had a '66 chevy truck with a 3.73 rear ge****t- it would do like 2500-2700 @ 60mph w/ a 29"-ish rear tire, if i remember right.
Not sure of gear ratio in rear end. ****** shifts smoothly 1st 2nd to 3rd but shifts from 1st to 2nd at about 5-10mph and 2nd to 3rd at about 15-25mph depending on how much gas i give it. I'm running 6.70/15 tires so they are decent size.
Top gear in a Turbohydramatic is 1:1- According to a common rpm calculator, you would have to be running a 6.38 axle ratio to hit 4500 RPM @ 60MPH, with a 29" tire in top ( third) gear. 2nd Gear in a TH400 is 1.52. 4500 RPM / 1.52 = 2960 If you're running 4500 RPM in 2nd gear @ 60 MPH, it should calculate out at more like 2960 RPM when you're in third gear with your current setup. That would mean that you are currently running a 4.11-- but if your tires are shorter ( less than 29"), it could be more like a 3.73. My guess is that you are running a 3.73 diff ratio with a 27" tire, and transmission that's in 2nd gear at highway speeds.
Also your speedometer could possibly be way off...but gotta be rearend gears will more than likely have to be changed
Don't forget that tire diameter is part of your final drive ratio. Feet traveled forward each revolution is surly part of the equation. Those old cars had some tall tires. My T-bucket winds out at 55 as well. It has a La Salle rear end that had 30in touring tires. Currently the T has lower profile 50 series tires from the 70's. It's a no brainer. 4 inches off the top leaves it lacking in top end. I will be changing my rims over to steel moonies to accommodate tall tires of the original hot rods in the 40's. You have a S10 rear end. If I'm not mistaken, those came with tires that would fit under a ½ ton. Same as my Nissan Frontier, it has full size ½ ton pickup tires under it. You can go to your local tire shop and find out what the S10's offered in sizes (for the year of the rear end) and compare them with what you have now. If you are going to run low profile tires, you need to up the ratio to compensate. Any rear end shop can tell you the the tire size vs. ratio. Since you have a large motor cranking that rear end, you will have no problem pulling a taller ratio than the 4-6 cyl. S10's offered. Heck, the kids put built 305's in them and burn rubber. That's one strong rear end. EDIT: LOL looks like 58 fridge and I had the same idea... I was typing when a friend called up and just had to tell me about her trip to the beach to see the Grunion Run. So yeah, all what ppl said here is good stuff!!!
My high school car was a '67 GS 400 with a built 455/TH400 and a 4:10 posi. It ran like a champ but it was done on the highway about 55 or 60. But man, it went like hell in a race! If you want your 500 to live a long healthy life you'd better get a higher gear.
While searching for info on tire sizes, I ran across these companies that are supposed to be giving cooper and coker a run for their money... DIAMOND BACK VINTAGE TIRES, 888-922-1642 www.dbtores.com. UNIVERSAL VINTAGE TIRE, 800-233-3827 sales@universaltire.com.
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