So i have 65 valiant and it was originaly with a 170 and a 3 speed manual.

i have swaped out the engine to a 225 and a 904 from 1970 something.

And here comes the problem,

When i drive around 65-70 mph the engine revs 4000-4200 give or take

its ben that way for years.but whit the manual and 170 i think it vas runing on mutch lower rpm.

this morning i was reading the repair manual and found out that the final ratio on both the manual and automatic gearboxes are 1.00:1
So why is it reving higer whit the automatic vs manual at the same speed?



And the rear axel question is:
if i want to change the ratio in it,what parts do i need to change?is it only the gear and pinion?what ratio would be good?can it be changed whitout problems.it is the original 7 1/4 axel from 65.

And yes i know it would be easier to change the whole axel to 8 what ever.

but the problem is that they dont grow on threes here in finland

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Plymouth Valiant 1965
225/4bbl/904/7 1/4
HEI ignition/msd blaster 2 coil/mallory module

Maybe due to slippage?

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

After writing the message i realised the same thing,automatics alvays slip a litle right?

But is it sliping too mutch?

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Plymouth Valiant 1965
225/4bbl/904/7 1/4
HEI ignition/msd blaster 2 coil/mallory module

10% slippage is too much for a stock torque converter at highway speeds. Are you certain your tachometer is correct? Give us the tires size and we can calculate the engine speed for a given road speed. A 170 with a manual transmission should have 3.55::1 gears in the axle.

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Joshua

Not too shore about the engine speed tach is sort of cheap and so on,but judging by ear its screaming on way to high revs.


but i think my tire size is 235/65-14 and i think the ratio is 3,55.

i have to check the size tomorrow to be sure.

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Plymouth Valiant 1965
225/4bbl/904/7 1/4
HEI ignition/msd blaster 2 coil/mallory module

You should be around 3200 RPM at 70 MPH with 3.55 gears and 235/60R14 tires. There are numerous RPM/speed calculators to play with, but this one is cool for Dodge fans. http://vexer.com/automotive-tools/speed-rpm-calculator

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Joshua

Is tach on 4 cyl setting?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

You really need to confirm what rear end gear ratio is currently in the vehicle.

One other note, the short stroke 170 "feels" much better in the 3000 to 4000+ RPM range, compared to a 225.

So between the loss thru the automatic's torque converter and the change to a longer stroke engine... the new combo is going to feel like it is working a lot harder, at your given highway speed.
DD

As Doc noted, the stock 170 will rev much higher than a similar 225. Or put another way, my Valiant used to have a stock 1bbl 225, button 904, & 2.93 axle. I was driving on the highway, 65-70mph, & hit the gas hard to pass a car. The trans downshifted, the engine made more noise, & my Valiant slowed down a couple mph.

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63 Valiant Wagon
225 - 4 bbl

Sorry for the long wait.i have been busy with life and Stuff.

Thanks for the answers so far,the only Thing i can confirm now is the wheel size and that's 235/60-14.winters here and i don't have reliable rpm meter so it's pointless to take it out on a ride.and i havent checked the ratio either,you know it's could and wet outside now.

But with that said i thank for the answers sofar and il get back to the subject in the spring

/speedy six

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Plymouth Valiant 1965
225/4bbl/904/7 1/4
HEI ignition/msd blaster 2 coil/mallory module

The very first thing you need to do in the spring is to get under the rear of your car and take the differential cover off and count the teeth on the ring and pinion gears..divide the pinion number into the ring gear number...thet's your gear ratio...your automatic doesn't slip at highway speeds ....if it did, your transmission would run so hot that it would self destruct....with a 3.55:1 ratio. that would be a bit much @70mph for the 225 engine...you need a 3.23:1 to calm things down @70mph....that's exactly what I did to my 1956 Dodge pickup truck....swapped out the 3.55s for 3.23s....now it's perfect around town at lower speeds and it goes great @70mph all day long.

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1956 Dodge 1/2 ton w/318,..1952 Ford 1/2 ton w/Hemi,..1940 Plymouth Business Coupe w/flathead six, dual carbs, and headers

If he has the diff cover off, clean the outer end of the ring gear where it mates to the diff...if it's a mopar rear with stock gears they will be stamped with the part number and diff ratio...bring some rags and brake clean...if you find nothing or the gear has rusted from disuse (sitting for a while...) time to count teeth...use a grease pencil to mark your first tooth (keeps you from being lost if the ring is over 40 teeth and you are falling asleep).

-D.Idiot

If its a open rear axle jack up one rear wheel turn wheel two turns and count the number of times driveshaft turns 3 1/2 turns you got 3.55, 3 1/4 turns you got 3.23 and so on, if its a posi jack up both wheels and turn them one turn