A few questions about my gears
#1
OK I'm not real up on performance upgrades and my new pony seems to have quite a few I need help on. Unfortunately, I don't know much about the stuff that has been done to the car I bought other than what I was told by the guy I bought it from, who doesn't seem to have been the person who had the upgrades done.

What I've been told is the car has 3.88 gears, a manual reverse valve body kit and the original cobra jet converter. I just started driving it and have noticed when I turn a corner the rear tires chirp like the rear end is solid no slipping. I can feel it grabbing and letting go in the rear. Why would that be?

Also, I now know that the manual reverse valve body kit makes my transmission act like a manual with no clutch. I must manually shift through the gears, which are reversed from normal. My question is, is there particular rules I need to know about when using this type of setup? I think starting out in 3rd is not a good idea, but should I ease off on the gas when I switch from one gear to another?

Thanks!
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#2
Good questions, but I'm not much help either.

I would think that letting up off the gas would help with the shift to save wear and tear, but I'm not 100% sure about that. Hopefully one of our other members will have more expertise in this area.
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#3
I can Help with the first question for sure. The rear end has some type of locking mechanism, such as a limited slip or a Detroit Locker. Which from your description of it grabbing and letting go is a characteristic of the Detroit under a partial load (easy on the gas). If you mash the gas it simply locks solid and spins both tires, 3gears or at least tries to. A limited slip you don't usually feel it when it engages or disengages. #2 As for the reversed valve body/ manual shift. this was done for performance driving/dragracing. You can slam the gears as hard as you want. But you must start in 1st gear and go through them all. This is my understanding of how they work from what I've read. Anyone else know more? As I'm not 100% positive? I don't have any first hand experience with a transmission set up this way? JTS 71 Mach1
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#4
If you wanna verify the gear size, put the car up on a lift, make a crayon marking on your driveshaft, spin your rear tires one rotation and then see how many times the driveshaft rotates. Should be 3.88 times.
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#5
Not an expert but have never heard of 3.88 gears in a 9" rear end 3.89 was an option I hope someone wasnt blowing smoke when they sold it to you.And if this is the same car he told you ran 9 second quarter mile I would like to see the time slip sounds impossible with those gears.Not trying to be rude just realistic.Sorry if I offended anyone.
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#6
I'm not offended in the least bit. I appreciate the straight answers and want nothing else. I have no doubt the gears have been changed and that someone went to a lot of trouble to build this car to do well in the 1/4 mile. I've had 3.73's put in my 1995 GT convertible and these gear are without a doubt lower. If anything I'm inclined to say they are much lower. 4.10 or even 4.56. The speedometer in my GT is off by 5 MPH at 30 with 3.73's and the speedometer in my 73 is off by 20 MPH at 30. The speedometer says I'm doing 50 MPH when I'm doing 30.

I have been trying to contact past owners to see if I can find the one who did the hot rodding that can tell me what I have.

One thing for sure is the Detroit Locker has to go. People look at me strange when I turn a corner and the tires squeal. Even with the Pro-Trac 50 Street Pro racing profile tires.

The engine is another mystery. It is not the original Q code but a 351 C 4V. I'm thinking why would someone who obviously is building a track racer to be a fast as possible take out a 351 CJ to put in a standard 351C? Just doesn't make sense. Generally when that is the case it is because I'm just missing some facts. When I changed out the starter I got the block cast numbers and it was DOAE-L with a cast date code of 0E22. I posted the numbers on a few boards and some said it was a "standard 2 bolt 351C" which made no sense. A few said I need to pull the pan to see if it was a 4 bolt block.

Doing some research of my own I found a lot of conflicting information on the Internet. While some called it the basic 351C others said it could be a Boss 351. The Boss 351 Registry list the DOAE-L as a Boss 351 cast number and even has a picture of a 1971 R code Boss 351 block with the DOAE-L date cast of 0D11 which is one month earlier than mine. Someone also made note that mine has screw in studs which is a Boss 351 head thing. Of course it could be just wishful thinking, but it would make more sense that the builder replaced the original CJ with a Boss. That would be a step up not down.

In any case I find half the fun is trying to determine what it is, but it can be frustrating at times so I really appreciate any input from more experienced people. I've been restoring old classics for some time but I have never been much of a hot rodder so I'm lacking knowledge in that area.
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#7

If someone pulled the 73 351 CJ and used a 70 351 C block with 70 or 71 heads it is an upgrade.

Other than 4 bolt mains the 73 Q code was a low compression motor.
Also if it was a late 73 motor it would have the smaller valves in the heads and the 70 combo would be a huge upgrade.
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#8
Your rearend could be several options, As stated a locker or some people have even welded open rears to lock both wheels. The most common change is to put a mini spool in an open carrier, either one is not desirable for street driving as you know. If you want a posi that will function on the street and still give you posi. Look for one of the trac lock units which is what Ford used. New ones are not the cheapest thing to buy, anywhere from 350.00 and up just for the center carrier.
The trans can be switched back to normal buy simply replacing the valve body, without pulling the trans.
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#9
Quote:If someone pulled the 73 351 CJ and used a 70 351 C block with 70 or 71 heads it is an upgrade.

Other than 4 bolt mains the 73 Q code was a low compression motor.
Also if it was a late 73 motor it would have the smaller valves in the heads and the 70 combo would be a huge upgrade.

IF you planned to keep the engine stock I can see this but would it still stand for plans to hotrod the engine? I mean if you were going to hotrod the engine wouldn't it be better to do it to the cobra jet rather than the 70 351C ? I don't know I'm just asking.
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#10
(12-19-2011, 12:15 AM)DCDetector Wrote:
Quote:If someone pulled the 73 351 CJ and used a 70 351 C block with 70 or 71 heads it is an upgrade.

Other than 4 bolt mains the 73 Q code was a low compression motor.
Also if it was a late 73 motor it would have the smaller valves in the heads and the 70 combo would be a huge upgrade.

IF you planned to keep the engine stock I can see this but would it still stand for plans to hotrod the engine? I mean if you were going to hotrod the engine wouldn't it be better to do it to the cobra jet rather than the 70 351C ? I don't know I'm just asking.

The 70 closed chamber heads and higher compression pistions would over ride any 73 CJ benifits. The 73 had 4 bolt mains but low compression and if it was a late 73 with small valve it was worse.
You never know if it the change was a performace thing or did the original motor die?

I have a 73 Q code mach1, bought it 6-7 years ago off the original owner
He put a 70 motor in it and a locker with 430 gears and line lock so he could race it.
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