To rebuild or not?

[cherrybomb]

I've got a 99' EB 4 door, with the 5.0L. She's got just over 100k on the clock, and in the ~3 years I've owned it, I've never changed the trans fluid. Presumably, it was maintained normally before I got it, but there's no knowing for sure.

On a recent trip from Southern California to Henderson, Nevada I noticed that when in overdrive the 4-3 downshift was VERY sluggish, and caused a significant amount of engine flare. Once arriving at my destination, other down and upshifts seemed a bit lethargic as well.

Once I parked it over night and let it rest/cool down things returned to "normal" but I was of course especially conscious of the shifts. I've always felt they were a bit soft, and when I am accelerating at full throttle the upshifts sometimes feel like they come late and are too soft.

Initially, I thought for sure I had some significant wear in the clutches and that I would have to rebuild for sure, however after doing some research here it seems as though I may just need to flush the fluid and possibly install a shift kit.

So the question is, considering the age of the transmission (100k+), the symptoms, and the work involved to drop the pan, do a shift kit, and flush the fluid. Should I just bite the bullet and rebuild, or not?

If I rebuild, I'll be following the 4r70w diary posted here, and the Thunderbird/Cougar website how-to's from which it's drawn. My truck is still stock drivetrain wise and should be making no more than stock horsepower, however I've addressed all the other "upgrades" I was interested in and the engine and transmission were the next on the list for upgrades anyway. In other words, more power is on it's way after I address the trans.

I intend to build the trans for the ~350 hp NA since my options are limited here in California and I'll likely be doing things over a longish period of time. When/if I exceed those numbers I'll go back into the trans and replace/add clutches and accumulators etc.

Of course, if I do the rebuild, I'll be replacing the Torque Converter as well.

So, what do you guys think? To rebuild, or not?

 

[rizzjc]

Well, it's not hard to drop the pan, replace the filter, and refill, so I'd do the first. 'Course, if it has NEVER had a fluid change, best to flush the whole system. A little more involved, and to me it's worth it to have a shop do it for me. But, make sure you replace the filter.

 

[CDW6212R]

I'd select a VB kit for your intentions, buy that and the Sonnax VB o-ring kit, and the rubber coated accumulators($17 on eBay). Do the VB work and drain the TC to get as much fluid as possible. Use good Mercon V, I'd skip the high dollar stuff until I knew that the VB was the cause of poor shifting. You don't want to invest $100 into fluid and then be needing a rebuild soon. If you do like good firm shifting, go for the HD VB kits, the $100 kits, not the $40 kits. Regards,

 

[PeteinCalif]

I suggest a rebuilt valve body. It wored for me.

I bought a rebuilt valve body from Central valve body. They advertise on Ebay. Call and talk to the owner, Donney. I found him very helpful. If you do the rebuild later you will still need a new valve body. My wifes 98 4.0 sohc Explored was really getting unpleasant to drive (85,000 miles and never serviced but was replaced by Ford at 35/40000 miles). I had a transmission shop install it when they changed the fluid and filter. Thats my story. Pete

 

[CDW6212R]

Unless the mileage is very high, swapping VB's is not the best idea. You do not know what the cause of the symptoms is yet.

Most Ford valve bodies are at issue with most symptoms, but the answer is not to replace any VB parts with stock parts. The majority of all VB kits are for improving a stock VB, not to replace anything with an identical component. Rebuilt VB's are basically at best a nearly new stock VB.

VB kits are basically designed to change stock components with much better aftermarket parts. The point is to correct design issues and the poor stock shift qualities. The aftermarket parts typically correct inherent weaknesses, leaks, or known deficiencies. Rebuilt VB's do not achieve that, they simply are supposed to give you what you had when it was new, which is not great.

Only if there are major wear issues in a VB is there any need to replace one or rebuild one. All VB's are designed and matched for that vehicle, rebuilt VB's are not and sometimes create new issues because of that.

I know that some companies with rebuilt VB's will also install the aftermarket kits(or TSB stuff like in the 5R55E). That is great if you know that you need a VB because the OEM unit is not worth using.

The 4R70W is a great transmission, and very strong. The main items that go out are few compared to weaker trannies like the 5R55E, A4LD etc. Read the rebuild diary as you have done, the main items to deal with for a rebuild are in there. Without high mileage or serious issues, try for a VB kit etc. as I mentioned. The costs are not wasted and you may get a lot more out of it before you are ready to build it. Regards,

 

[cherrybomb]

Thanks for all the quick input.

I think I'll go ahead with just doing a VB kit and fluid replacement. Now to start buying parts.

CDW, I assume you're referring to a TransGo HD Kit. Something like this kit? This is the only one Summit has with "HD" in the part number. There is one kit that costs more but only because it comes with a video. I think I can handle the job without it.

Who knows, maybe this way I'll save myself the rebuild until I do have > 350 HP or so. ;-)

 

[CDW6212R]

TransGo has more choices now than they used to. That link is for a kit without any instructions. I'd see if they are still on eBay for around the $90 range, they used to be about $110 for the AODE/4R70W.