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Discussion Starter · #1 ·
My 1970 mustang is experiencing some odd symptoms. The car will rev up then slam into gear. (* no slipping) once in gear its fine. shifts 1,2,3 no problem. Once i let off the acceleration peddle it pops into neutral. The vacuum lines are good and the transmission fluid level is fine as well.
 

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If it's slamming into gear then IMHO I would look at the valve body...... likely that the valve(s), springs, etc. are sticking doe to dirt, varnish buildup, etc.
 

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Discussion Starter · #4 ·
If it's slamming into gear then IMHO I would look at the valve body...... likely that the valve(s), springs, etc. are sticking doe to dirt, varnish buildup, etc.
would that cause the popping out of gear and going into neutral? it sounds like a mechanical issue, but it also sounds like a pressure issue?
 

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Most common reason for this is always going to be fluid. Did you check it while idling? If it's overfilled or underfilled, it will cause exactly this problem. Sticking valves would be my second guess. If your vacuum modulator is disconnected, it will slam into 2nd really late (even when driving gently) and try to get back into lower gears very early when you decelerate too.

If you put in something besides Type F fluid, sometimes that will cause foaming, and that can also cause some erratic shift problems!

Also - welcome to AFM!
 

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Discussion Starter · #7 ·
Most common reason for this is always going to be fluid. Did you check it while idling? If it's overfilled or underfilled, it will cause exactly this problem. Sticking valves would be my second guess. If your vacuum modulator is disconnected, it will slam into 2nd really late (even when driving gently) and try to get back into lower gears very early when you decelerate too.

If you put in something besides Type F fluid, sometimes that will cause foaming, and that can also cause some erratic shift problems!

Also - welcome to AFM!
Thank you sir,
It definitely feels like a pressure issue. I thought a mod valve would be to simple. I found a guy online who explained these exact symptoms and took it to a shop. Turned out being the front pump rings. Any thoughts on that?
 

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Thank you sir,
It definitely feels like a pressure issue. I thought a mod valve would be to simple. I found a guy online who explained these exact symptoms and took it to a shop. Turned out being the front pump rings. Any thoughts on that?
Well, the simple truth is, once you get past "It has fluid", "It's not foamy", "Vacuum is hooked up properly", and "Shift selector is where it should be in relation to the shifter", you're probably going to have to open the case to find out what the problem is anyway. Crack in the case? Busted pump? Varnished valves? Who knows. But thankfully, the old C4 is easy to work on, and very tough. I'd be surprised if it's something internally broken. Usually the rings in these aren't an issue - but we are talking about something that may be 55 years old here too, so it's possible!
 

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Discussion Starter · #9 ·
Well, the simple truth is, once you get past "It has fluid", "It's not foamy", "Vacuum is hooked up properly", and "Shift selector is where it should be in relation to the shifter", you're probably going to have to open the case to find out what the problem is anyway. Crack in the case? Busted pump? Varnished valves? Who knows. But thankfully, the old C4 is easy to work on, and very tough. I'd be surprised if it's something internally broken. Usually the rings in these aren't an issue - but we are talking about something that may be 55 years old here too, so it's possible!

your right about breaking it open. I sat through some rebuild video's and although transmission are a tricky science it doesnt seem all that hard to break it open and inspect some parts. Good news is i have a second transmission and this one will be purely education for me
 

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your right about breaking it open. I sat through some rebuild video's and although transmission are a tricky science it doesnt seem all that hard to break it open and inspect some parts. Good news is i have a second transmission and this one will be purely education for me
C4 is actually one of the best transmissions to learn on, because of its simple design. Aside from the complicated hydraulic circuits, the actual operation of the transmission is very easy to understand.

Back in the day, the C6 was regarded as the better transmission between Ford's automatics, but with modern friction materials and parts, the C4 can be built to handle 1500+ horsepower reliably, and it still uses a lot less power and weighs less than the C6. For an itty bitty transmission, it punches way above its weight. Out of the old 60s automatics, most people would say the Powerglide is best (for dragstrip use) because it has the lowest frictional losses, but it's only a two-speed. Past that, it's a tossup between the legendary Torqueflite 727 (a bigger, heavier transmission also with Simpson gearset) and Ford's mighty mite, the C4.
 

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Discussion Starter · #11 ·
C4 is actually one of the best transmissions to learn on, because of its simple design. Aside from the complicated hydraulic circuits, the actual operation of the transmission is very easy to understand.

Back in the day, the C6 was regarded as the better transmission between Ford's automatics, but with modern friction materials and parts, the C4 can be built to handle 1500+ horsepower reliably, and it still uses a lot less power and weighs less than the C6. For an itty bitty transmission, it punches way above its weight. Out of the old 60s automatics, most people would say the Powerglide is best (for dragstrip use) because it has the lowest frictional losses, but it's only a two-speed. Past that, it's a tossup between the legendary Torqueflite 727 (a bigger, heavier transmission also with Simpson gearset) and Ford's mighty mite, the C4.
How does the C4 line up against the TH350 by Chevy? I’ve heard those are tanks as well. A lot of people use them for drag car because they can handle so much.
 

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C4 is superior to the TH350. It's got just as much strength (or more), but is lighter. Of course, it does depend on what parts you put in it! In stock form, they're about the same, and even modified, I think they have similar potential - but the C4 is a bit smaller and has less frictional loss than a TH350. Similarly, the TH400 is a big beefy sonofagun, much like the C6, and in the same manner, pretty much nuclear blastproof even in stock form. But heavy, and steals more horsepower than its smaller brother.

Edit: I had to look up some numbers to make sure of my facts. I was surprised to see that these transmissions are closer in size than I thought they were! TH400 is not much heavier than a TH350, nor is TH350 much heavier than a C4. However, the taxable horsepower on a C4 beats 'em all. It's really efficient, and typically only steals about 25 horsepower, which is not much worse than some manual transmissions! None of these other automatics can touch it in terms of efficiency (much less the big heavy but "you can't hurt me" C6).
 

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C4 is superior to the TH350. It's got just as much strength (or more), but is lighter. Of course, it does depend on what parts you put in it! In stock form, they're about the same, and even modified, I think they have similar potential - but the C4 is a bit smaller and has less frictional loss than a TH350. Similarly, the TH400 is a big beefy sonofagun, much like the C6, and in the same manner, pretty much nuclear blastproof even in stock form. But heavy, and steals more horsepower than its smaller brother.

Edit: I had to look up some numbers to make sure of my facts. I was surprised to see that these transmissions are closer in size than I thought they were! TH400 is not much heavier than a TH350, nor is TH350 much heavier than a C4. However, the taxable horsepower on a C4 beats 'em all. It's really efficient, and typically only steals about 25 horsepower, which is not much worse than some manual transmissions! None of these other automatics can touch it in terms of efficiency (much less the big heavy but "you can't hurt me" C6).
Man you know a great deal about trannys.
 

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Man you know a great deal about trannys.
I think it's worth mentioning, the TH350 and 400 are both great transmissions. If you have a GM, it would not make sense to convert and buy expensive bellhousings to use a Ford transmission, nor would I use a GM transmission on a Ford, unless you're at top level dragstrip competition with an engine that makes tons of torque. Then the lower power requirement of a two-speed Powerglide starts to make sense.
 

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I think it's worth mentioning, the TH350 and 400 are both great transmissions. If you have a GM, it would not make sense to convert and buy expensive bellhousings to use a Ford transmission, nor would I use a GM transmission on a Ford, unless you're at top level dragstrip competition with an engine that makes tons of torque. Then the lower power requirement of a two-speed Powerglide starts to make sense.
I have another question for you. I don’t know what exhaust to get for this car. Obviously once I fix tranny id like it to sound great. Right now it’s just open headers and I feel a bit guilty driving it through the neighborhood on test drives. I like the growl of the cobra, saleen, Shelby and Mach 1 mustangs. I don’t even know if that attainable on the older applications. I want something low and clean with no raspyness. Something that’s not loud in the cabin.
 

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I have another question for you. I don’t know what exhaust to get for this car. Obviously once I fix tranny id like it to sound great. Right now it’s just open headers and I feel a bit guilty driving it through the neighborhood on test drives. I like the growl of the cobra, saleen, Shelby and Mach 1 mustangs. I don’t even know if that attainable on the older applications. I want something low and clean with no raspyness. Something that’s not loud in the cabin.
Most newer cars utilize an "X" pipe, which tends to equalize pulses from side to side, making it sound 'smoother' and more 'formula 1' like. The other tonal aspect that I think you are looking for is probably a result of the chambered mufflers that are typically used on newer cars. It has a throaty, hollow sound. Flowmaster is the typical go-to for a muffler of this design. In order to keep volume down, you'll want longer ones; avoid the 44 series, as their stubby length does not do much to relieve volume level. Chambered mufflers: Mating call of the modern millennial. To an old fart like me, they sound like Black Cat firecrackers in a trash can. Nope, I'm not prejudiced or anything. ;)

Personally, I prefer the mellow tone of Magnaflows, but then again, I also love the savage rasp of glasspack mufflers. Generally speaking, the longer the muffler, the quieter. It does not mean additional performance loss, just more room for the pulses to interfere with each other and come out of the exhaust with less noise.

If I were you, I'd check out Youtube samples of "Magnaflow" "glasspack" "flowmaster" and maybe "turbo muffler" to get a clear idea of the tonal quality on each. Listen to multiples of each kind to get the best understanding, because mic quality varies a lot, as well as how it sounds on cars with headers, cast iron manifolds, H-pipes, X-pipes, no crossover, and different cam types.
 

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Most newer cars utilize an "X" pipe, which tends to equalize pulses from side to side, making it sound 'smoother' and more 'formula 1' like. The other tonal aspect that I think you are looking for is probably a result of the chambered mufflers that are typically used on newer cars. It has a throaty, hollow sound. Flowmaster is the typical go-to for a muffler of this design. In order to keep volume down, you'll want longer ones; avoid the 44 series, as their stubby length does not do much to relieve volume level. Chambered mufflers: Mating call of the modern millennial. To an old fart like me, they sound like Black Cat firecrackers in a trash can. Nope, I'm not prejudiced or anything. ;)

Personally, I prefer the mellow tone of Magnaflows, but then again, I also love the savage rasp of glasspack mufflers. Generally speaking, the longer the muffler, the quieter. It does not mean additional performance loss, just more room for the pulses to interfere with each other and come out of the exhaust with less noise.

If I were you, I'd check out Youtube samples of "Magnaflow" "glasspack" "flowmaster" and maybe "turbo muffler" to get a clear idea of the tonal quality on each. Listen to multiples of each kind to get the best understanding, because mic quality varies a lot, as well as how it sounds on cars with headers, cast iron manifolds, H-pipes, X-pipes, no crossover, and different cam types.
Interesting take on the millennial mating call but your all to right. New school Muscle Cars sounding like soda cans and Honda civics. I’m much like you prefer a clean quality sound while stepping on the gas but low at idle. Glass packs sound great with a bigger cam providing that pause between firing. My Buddy had a 67 Chevy with a 383 and a larger cam and glass packs. It sounds amazing and even tougher on a cold start.

I have an x pipe o plan to put in. Better airflow like you said. A lot of people would assume it would restrict air flow but it’s the exact opposite.

I done some YouTubing and audio isn’t the best in most videos but your right I’ve got a better idea but havnt found what I’m looking for. Magnaflow sounds really great and clean so far.
 

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FWIW I've put Magnaflow setups on quite a few cars (and trucks), and I like the fact you hear the engine when you're on the throttle, but they don't make your ears bleed when you're just cruising. I must be getting old, or it's just that I grew tired of my ears ringing from 2 chamber Flowmasters in my old Fox Mustang.
 

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FWIW I've put Magnaflow setups on quite a few cars (and trucks), and I like the fact you hear the engine when you're on the throttle, but they don't make your ears bleed when you're just cruising. I must be getting old, or it's just that I grew tired of my ears ringing from 2 chamber Flowmasters in my old Fox Mustang.
John, I feel exactly the same way except that I've always hated Flowmasters. I had Cherry Bombs (with no pipes) bolted direct to my Aluma-Kote Blackjack headers back in the day. lol
I love the mellow rumble of Magnaflows. They're not annoying out on the highway, but they sound mean when you're being rowdy. They are my favorite.
 
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