727 questions

[rikubot]

Hi guys/gals

I have a newly rebuilt 727 behind the 440 in my '69 Charger and I had a question about the feeling of the "drive" gear. It's a '71 model tranny and everything was gone through and a rebuild kit from Mancini was installed, plus a new reverse band. The only thing not gone through was the valve body, which appeared to have a shift kit in it. Anyway, from a stop through first gear, the acceleration seems inconsistent and almost like it slips. When in first and second on the gear selector, this is not the case. I've never ridden in another 727 BB car, so I have nothing to compare it to. Is this a valve body issue? The guy who rebuilt my tranny is a pretty good mechanic, so I'm not sure what the deal is. Thanks in advance,
- Mike

[Kern Dog]

I only saw one question, not 727 of them.

[c00nhunterjoe]

Could you elaborate on what inconsistant means? What is different between 1st gear in drive and 1st gear in 1 as far as acceleration goes?

[John_Kunkel]

Anyway, from a stop through first gear, the acceleration seems inconsistent and almost like it slips. When in first and second on the gear selector, this is not the case.

Sounds like a faulty overrunning clutch (sprag).

In Drive, 1st gear doesn't have the rear band applied so any fault in the sprag will cause slippage, once shifted to 2nd and beyond the sprag isn't used. When the shifter is placed in 1, the rear band applies and takes over the function of the sprag. It's unusual to have a failure in a fresh trans unless the builder assembled the parts incorrectly (reversed the position of the springs and rollers) or never checked them at all.

Unfortunately, there's no way to accurately test the sprag without disassembling the trans, the sprag is all the way in the back of the main case.

[rikubot]

Could you elaborate on what inconsistant means? What is different between 1st gear in drive and 1st gear in 1 as far as acceleration goes?

It feels to me like slippage, only in the first gear while in drive. 1st feels solid when the shifter is actually in the first gear.

[rikubot]

@John Kunkel,

That would definitely explain the problem. I am not sure if my buddy messed with the sprag,but I will ask him. It reminds me a lot of how it drove before the rebuild but not as bad. Maybe he reassembled it exactly how he pulled it out, or didn't touch it at all. What are the risks of driving it like this?

[rikubot]

About how likely do you think it is the sprag? I'm not too worried about the cost or work to drop it and pull it apart, but if it's not that that would be a bummer.

[rikubot]

I only saw one question, not 727 of them.

I'm just getting started! 

[Kern Dog]

 

[rikubot]

Bump

[John_Kunkel]

What are the risks of driving it like this?

If the sprag is the problem, you're at little risk during normal driving but if you put your foot in it hard you risk exploding the trans. Sprag failures are the cause of explosions 99% of the time.

[c00nhunterjoe]

Google "727 sprag failure" and take a look......

[rikubot]

Good Lord that was terrible, I'm thinking I might not drive my car until I get this issue resolved...

[68CoronetRT]

Might as well ask in this thread vs starting a new one.

I'm starting to look into a 833 to 727 swap. I'm over the 4 speed and want a nice reverse manual valve body auto.

So my questions are basically about upgrades. I want to order a mail order trans from Cope but was wondering if anyone can suggest upgrade parts and what's worth the money. Car is mainly a street car with the occasional strip night couple times a year. Going with the PTC Converter(Neutral), and B&M Flexplate for the externally balanced motors. I also want to retain engine braking from 3 to 2.

[John_Kunkel]

No matter how you build it you'll always have engine braking from 3-2, it's 2-1 engine braking that depends on the valve body you choose. If the valve body has low band apply (LBA) you'll have engine braking in 1st gear, if no LBA there will be no engine braking in 1st.

A fully automatic valve body will always have LBA, only the manual valve body will come either way.