Ford 4R70W question

[Falcon_LS]

In my Grand Marquis, the transmission seems to slip at the 35 MPH mark, although it happens sometimes at other speeds as well. Just that the 35 MPH mark is what I kept noticing, but it doesn't always do it either. The engine revs higher for one second, there's no acceleration and then it continues to accelerate. Initially, I reckoned this may be gear shifter wear, but I checked that just to get that out the way, and it isn't the issue. So I added half a bottle of Auto-Rx, and over the course of the past 1,000 miles, it has helped some and there is much less slipping right now compared to when I got the car 3 weeks ago.

I'm not sure what ATF the previous owner used, but I have a feeling it's your typical ACDelco Type III as opposed to Mercon V as recommended by Ford (Type III is a bit of a lighter shade of red but then again it's not guaranteed it is Type III). People go for the cheapest option possible here and their mentality is "It's American fluid in an American car so it should work".

Given the situation, should I leave the ARX in there for longer, or should I do a cooler line flush with fresh Mercon V and then add a dose of ARX to clean up the transmission before repeating the flush?

Thank you!

 

[Colt45ws]

I would change with Mercon V with no ARX and then do that again in 5k or so.
I assume youve run it hard some during this ARX clean? I noticed when I did it on another trans I didnt really notice a difference until I was late for school one day and beat the carp out of it.
It was much better after that.
I hate to sound like a koolaid drinker, but is it possible to get the parts and stuff to do a JMod over there?

 

[Falcon_LS]

The JMod is actually on my list.

I just have a couple of other things to sort out first. Replacing my alternator with a 135 amp unit (one of the diodes are dead) and then doing some suspension work (PI springs and shocks).

 

[spasm3]

I have to ask, whats JMod stand for?

 

[The_Jeff]

Jmod is a valve body tweak to firm it up.

 

[Trav]

OP given the operating temps it may be just a sticking valve body due to varnish.Do not start beating the snot out the transmission for the mechanic in a can to work.
I cant tell you how sick i am of hearing "beat on it" or "drive it like you stole it" for ARX to work,it either works or it doesn't.
IMO beating on a transmission especially a sickly one isn't going to make anything better if anything it will just damage the unit.

For sticking valve bodies ARX may not be the optimal product as it does not do well on varnish,BG trans flush works very well,run it for 20 min,shift it through the gears and flush it out.
Fill with Mercon V and add 2 bottles of lubeguard red in a transmission with this capacity when refilling.Drive it normally afterwards.

 

[racecougar]

I'd do the Jmod and change the fluid over to Mercon V as soon as you can. A trans cooler would certainly be a good idea as well.

 

[Falcon_LS]

Originally Posted By: Trav
OP given the operating temps it may be just a sticking valve body due to varnish.Do not start beating the snot out the transmission for the mechanic in a can to work.
I cant tell you how sick i am of hearing "beat on it" or "drive it like you stole it" for ARX to work,it either works or it doesn't.
IMO beating on a transmission especially a sickly one isn't going to make anything better if anything it will just damage the unit.

For sticking valve bodies ARX may not be the optimal product as it does not do well on varnish,BG trans flush works very well,run it for 20 min,shift it through the gears and flush it out.
Fill with Mercon V and add 2 bottles of lubeguard red in a transmission with this capacity when refilling.Drive it normally afterwards.


Thanks a lot!

Originally Posted By: racecougar
I'd do the Jmod and change the fluid over to Mercon V as soon as you can. A trans cooler would certainly be a good idea as well.


Being an export model, the transmission cooler is standard.

 

[Falcon_LS]

An update. When I first got the car and stripped the interior to clean it up, there was a receipt from a garage for an oil and filter change (Motorcraft Syn Blend 10w30 and FL-820S). I reckoned this was where my vehicle was serviced before so I paid them a visit to see if they have any records of any sort.

One of the so called 'techs' recognised the vehicle and said the previous owner would bring it in often for its regular service intervals. Had a word with him about the transmission service, and it had a simple drain and refill roughly 2 weeks before I purchased it. I asked what fluid they used and he showed me a bottle of Motorcraft Type M, which is the only Motorcraft ATF they have, claiming 'genuine' fluid was used! When I said this was the WRONG fluid, he goes it's all the same...this costs $2.50 a quart whereas Mercon V $5.10 a quart.

Needless to say, I got 24 quarts of Motorcraft Mercon V and flushed it all out. The slipping has significantly reduced, but there's till a very slight bit of slipping. Going to drive it for a while, then add Automatic Transmission Cleaner before I do another cooler line flush.

 

[Schmoe]

That transmission is notorious for slipping. It's why that particular transmission is so smooth for a while. I put in a Factory Tech shift plate on my F150. Didn't really cost much more as you got to open up the bottom of the transmission any way to do the Jmod. If you drive "normally," you won't really notice the shift plate except it will grab a little quicker and shift faster. Now if you floor it from a stop, it will literally throw your head back into the seat when it grabs second. No sliding going on there. Well worth the money!

 

[Trav]

Use about 3 cans of the cleaner.Dont forget to get some lubeguard red or platinum even if it has to be ordered.2 bottles should do it,it may make a significant difference in this unit as it provides additional protection from heat and does improve shift quality.

Once you satisfied the transmission is functioning properly you can have it checked out with an advance scan tool,it can tell you the amount of actual transmission/converter slippage.0-1 is the normal range for new and units in good shape of the 4R70W and 4R100W type,i see 1 most of the time with the Autoenginuity and Genisys scanner.