Swap out, rebuild, or improve broken 727 tranny on Newport?

[Henrius]

Looks like setting up several years did something to the automatic transmission of my 1972 Newport. It had about 100,000 miles on it since its only rebuild a long time ago. Now it just sits there when I start the engine, shift it to drive, and press the accelerator.

I don't know anything about repairing/rebuilding automatic transmissions. The shop is giving me the option of swapping out the original for a rebuilt one, or rebuilding the transmission in the car now.

I always think: Is there a way to improve what was the in car, for efficiency's sake? For instance, I've heard there were some 727s with a 3rd gear lockup, that might improve gas mileage. One thing I am not interested in is making this heavy Newport a muscle car.

I would appreciate what other people think about transmission options for this car.

 

[BigblueC]

Have you had anyone other than the shop who wants to replace the trans look into why it isn't functioning? That's where I would start as it could be a simple/cheaper fix than a complete rebuild/replace.

If I were in the situation of rebuild or replace I would either: a) have the original trans rebuilt to O.E. specs, maybe some updates, or b) keep the original trans on a shelf and replace it with a newer overdrive trans (which will most likely involve re-gearing the rear end).

It just depends on your budget and what you want to do with the car. Either way I suggest not loosing any factory pieces, like your original trans.

 

[oliver]

So the car sits for a while and then doesn't move when you throw it in gear? Try letting it idle in Neutral for a good 10 seconds before putting it in "D" and see if that helps.

 

[Ross Wooldridge]

...or shift right down to low 1.

 

[Big_John]

Also check the fluid while idling in neutral. You probably know that, but I like to cover the simple stuff first.

I would go for having your trans rebuilt if possible.

 

[CudaJames69]

Check the fluid when you first start it. How far up the stick is it ? If it's very high , the converter is draining back into the trans . Could be front seal or converter problem .

Put it in reverse first , higher pressure in reverse .

 

[Henrius]

Have you had anyone other than the shop who wants to replace the trans look into why it isn't functioning? That's where I would start as it could be a simple/cheaper fix than a complete rebuild/replace.

If I were in the situation of rebuild or replace I would either: a) have the original trans rebuilt to O.E. specs, maybe some updates, or b) keep the original trans on a shelf and replace it with a newer overdrive trans (which will most likely involve re-gearing the rear end).

It just depends on your budget and what you want to do with the car. Either way I suggest not loosing any factory pieces, like your original trans.

Thanks for the info. Yes, I am trying to have the restoration shop diagnose the problem, instead of sending it directly over to the transmission shop. The transmission was "slippery" after not using the car for a few weeks when I last drove it. Now they say it will not move at all.

What are these newer overdrive transmission you are talking about? I might be interested in that.

 

[BigblueC]

Well "slippery" can be a lot of different things, even just a filter/fluid change. Are you feelin' lucky?

What are these newer overdrive transmission you are talking about? I might be interested in that.

I have to confess, I'm also a Chevy guy, and have no experience modifying Mopar stuff. If we were talking Chevy, you would have options like 200/700r or the electronic controlled 4L60/70/80E. I'm sure there are similar mopar options, and that there are members here that are knowledgeable in these types of swaps. But beware, these "simple" swaps can get complex and expensive quickly (modified trans tunnels, shorten drive shaft, relocating cross members, re-gearing the rear end, etc.). I do know that bell housing to put a 200/700r behind a big block mopar are readily available, but that's blasphemy and I offer my apologies to the members.

If this was my Chrysler, I would have the original trans rebuilt by the most reputable shop that I could find. but it's your car and you have options. Just make sure that you have a plan of action before starting.

 

[Gerald Morris]

I just got the original 727 for Mathilda, our 66 Newport rebuilt yesterday and it made a WORLD of difference! I got it done for a modest price too by a shop which has been in business for 42 years. Both of the owners have worked on 727s over this timespan, and their honesty and rock solid knowledge convinced me. I'm ecstatic with the results now. I'll post this at length on my own, but if indeed you've got more than a trivial issue, find a good shop and have it built to OE spec, with maybe some modest upgrades like a shift kit or such.

Lockup torque converters and overdrive will take you past the original 727. I suspect overdirve is beyond any of the 727s per se, though their descendants like the 36RH have it. Don't know if such can be made to bolt on to a B/RB block motor. You CAN change your rear end gears up to some nice tall ones! That will give you much of the benefit of overdrive and is very feasible. Try something like 2:76 or 2:91.

 

[Henrius]

I just got the original 727 for Mathilda, our 66 Newport rebuilt yesterday and it made a WORLD of difference! I got it done for a modest price too by a shop which has been in business for 42 years. Both of the owners have worked on 727s over this timespan, and their honesty and rock solid knowledge convinced me. I'm ecstatic with the results now. I'll post this at length on my own, but if indeed you've got more than a trivial issue, find a good shop and have it built to OE spec, with maybe some modest upgrades like a shift kit or such.

Lockup torque converters and overdrive will take you past the original 727. I suspect overdirve is beyond any of the 727s per se, though their descendants like the 36RH have it. Don't know if such can be made to bolt on to a B/RB block motor. You CAN change your rear end gears up to some nice tall ones! That will give you much of the benefit of overdrive and is very feasible. Try something like 2:76 or 2:91.

Thanks for the advice. What is a "shift kit?"

The lower axle ratio lower the engine RPM but also reduces acceleration, right? Do you happen to know what the factory rear end gear was in your car?

 

[BigblueC]

The lower axle ratio lower the engine RPM but also reduces acceleration, right?

Yes. The numerically lower gear ratio, say 2.71:1, will have less mechanical advantage than a gear ratio of 4.88:1. When you talk to someone about gear ratios the terminology is flipped. 4.88 is a low/short gear, 2.71 is a high/tall gear.

A shift kit will modify the shifting characteristics allowing you to "tune" the transmission. Typically when someone talks shift kit, there talking about making the trans shift quicker and firmer.

 

[moper]

Later model OD for a mopar big block is not easy or cheap. I'd not bother. If you want an OD gear, just buy the Gear Vendors OD unit and install that. These cars ran their lives at highway rpms with a 3 speed transmission. IMO OD is not worth the money until you're adding more gear for acceleration.
Have your 727 rebuilt. It's not expensive in the big picture. Have a reputable place do it, get a warranty, make dur they replace the convertor or send yours out for flushing, and you're good to go.