I am just curious if the two axles will swap out.
Which is the best of the two axles?
I have a vibration in my 88 with the 8.8 that starts around 55 to 60 mph all the way up to about 70 mph. When you let off the gas it is a bit more pronounced. Since I am not using the 85 right now I thought about swapping out the complete axles.

Another issue might be that the 85 has a 2 piece drive shaft while the 88 has a single aluminum drive shaft. Both drive shafts have new U-joints and the 85 has a new bearing carrier and rear transmission mount.
i don't know if i would need to swap the cross members or not..
Both vans are 138 WB with 302 engines and AOD transmissions
Both are, I believe 3.55 gears.

Thanks
Anna

 

Just a thought..........

Maybe get the drive shaft "Balanced" first??

I know that Fleet Pride are all over the place, and they can build/make drive shafts and also balance new/old drive shafts at a reasonable price.

I once had a Jeep drive shaft build, from the OEM yokes, and given the need length, new shaft, re-used yokes, new U-joints, balanced, out the door for like $150.

Not saying that you could have a problem with the differential now, like worn pinion, bad bearings, ect. Just saying that variable vibrations at speeds could be many items, like off balanced drive shaft, said problems with diff. out of balanced tires, tire belt slips, ect.

Also.......if the drive shaft is 2 piece, you could have a bad center support bearing.

 

Thanks Wildman
Yes balance the drive shaft is one of the things on the list. I had a drive shaft shop replace the U-joints but he said the joints were factory and there was no damage on the shaft so I shouldn't need to balance it.
Well I started noticing a ping like sound (best way to describe it as aluminum really doesn't ping like steel) and I ran across a TSB on the aluminum drive shafts around that year and Ford was replacing them because the Yoke is crimped on and that is where the noise comes from. Well that TSB was around 1990 so no help from Ford now. I talked to the guy at the drive shaft shop and he said he would make me a good deal on balancing and welding the yoke to the shaft.
I still need to do that and that could very well be the problem.





There are several things going on and I need to get busy and check them out.

The left rear wheel has a very very slight wobble in it. i did not check it again since i have had the tires rotated. BTW balancing and rotating the tires did not change the vibration coming from the rear.
I pushed and pulled on the driveshaft checking for a bad pinion bearing and saw no play 10k miles ago.

Next drive line problem...
The clunk when the transmission shifts into OD at lower speeds depending on conditions, ie, throttle, no throttle, up or down hill ect. At higher speeds say getting on the freeway, it does great and you hardly feel it shift to OD. BUT at lower speeds when it does clunk, it almost always feels like it is in the rear axle.
Last night I kept it in D and pushed and let off the throttle several times under different conditions and there is absolutely no clunk or loose feeling in the drive train from inside the van.
I have only put a little over 10kon the van since i have had it and it has always had all the symptoms mentioned above. I took it to a old transmission shop in town a few weeks ago and the owner test drove it. He said he had an older ford truck that has been doing the clunk for years and to just drive the van. He said everything else seems just fine but he didn't drive it at higher speeds, just in town.

So I am just tossing ideas and thoughts around what it might be and what I should do about it. i plan on keeping it as a daily driver for years to come and so don't mind doing what needs to be done to keep it in top shape. I am also not sure of the mileage on it because I know it has rolled over at least once but all the signs are that it only has 115k on it.. I am not sure how much compression would tell me about the mileage (100k vers 200k) but it had 180psi all the way around Dry test (no oil in the cylinders) and just barely warm when I tuned it up last. Also when i had the plenum off a while back it wasn't really all that dirty inside compared to other pictures I have seen of some.
The intake before and after cleaning it by hand at the car wash..

 

While on the subject of rear axles, If it did come down to rebuilding it, The local shop said around 2k!!!
Humm, I have tossed around the idea of buying a master rebuild kit, both axles and bearings and giving it a shot my self. there is some really good videos out here on how to do it and my dad besides owning a mechanic shop when I was younger, he was also a machinist tool and die maker so I have some basic common knowledge that would help out. I guess it is just kind of intimidating because I have never done it.. I did pull the 9" differential out of the housing and inspect it (for what ever good that dis as i didn't know what to really look for except for a visual inspection and rotate by hand. I did that because the 85 had sat for a long time and i was just replacing the axle bearings and wanted to clean the housing. Someone had been in there before because there was no factory gasket, only black sealant.



I am wondering though like you said, perhaps the drive shaft is the vibration and the clunk that feels like it is coming from the rear axle when it shifts into OD is just being transferred from the transmission.

Another thought might be,, last year when I replaced the springs, shocks, radius arm and i-beam bushings, I was also going to replace the spring shackle bushings. I even dropped one side of the axle and pulled out a front leaf spring bushing only to learn that my new bushings would not fit so I put it back together.
But I read somewhere that worn springs and bushings can through off the pinion angle enough to cause vibrations. They physically don't look all that bad though.
What is your thought on this? If the spring shackles and the leaf spring bushings that the shackles mate to at the rear were sagging a bit along with the springs....




BTW,, I was just looking at a pic i took of the yoke on my 88 when I had the drive shaft out.. I just noticed that the nut holding the yoke on is red... Do you think that is factory or could someone have been in there too?

 

I somewhat remember the old aluminum shaft problem, about the crimped yokes, but that was Long ago.......

From your one picture, it looks like the shaft is plugged welled,or is that for one of the balance weights???

The shifting clunk, could it be from the torque converter locking up for overdrive?? Was that not a problem with other's?? If the 'ole time tranny guy told you to just drive it, that's your answer........just drive it *of course, not like you stole it, or something.....*

The red nut at the pinon flange, I'm sure that's OEM, I'm sure they used some sort of ID for that special "crush Nut" for setting the backlash.

You wrote about a rear tire wobble?? Was it the tire or the rim bent from bouncing off curbs?? That would cause a tire to wobble, but should show up with spin balancing.


Needed to add........When you clean out the differential, did you find any foreign particles in there, like silver looking oil, metal chunks?? If not, your good to go.

 

A year or so I had found a page that listed all the TSB's but I am a sloppy secretary and it is buried somewhere in the thousands of unsorted bookmarks I have...

I am not sure what that is for on the driveshaft. I will ask the guy when i take it to be balanced...

The clunk,, i have read posts about this where many say its a normal and other posts where people say no. Either way it is a common complaint with the AOD. Since I got the 88, my 85 has been sitting with the new gas tank and all the associated parts inside the van but I don't remember it clunking when shifting to OD. The 85, i never got used to the shifting. I believe it had some mods done to the transmission because when i first got it, it wouldn't shift out of first till around 25mph and 2nd to 3rd at around 35 mph and even then you had to let off the gas. I changed the fluid/filter and even cleaned the governor. I used a gauge to set the TV pressure as low as safely possible and got it shifting a bit better.
I had a1990 town car and a 81 Mercury colony park wagon both with OD,s and they didn't clunk. Somebody should slap me for selling the wagon as i helped a friend put the 100k mile warranty 302 long block in it before he sold it to me. He drove it about 30k before he sold it to me and a truck backed into the front end of it. The rebuilt AOD in it only had around 50k on it. Sold $500 for scrap!!

You think a bad converter could cause that clunk?

The rear wheel wobble, I noticed it when I had the U-joints replaced in the drive shaft. Just very slight and I haven't checked it since. I think I read in my manual that I need to raise it up, remove the wheel and drum. Then set up a dial indicator with magnetic base attachment to check the (hub flange?) to see if it is running true or not.

These days I cant physically do all the work myself and my son flew the coup so I have to get my neighbors husband and brother to help out.. Sucks getting older but that worked out great last summer when we rebuilt the front end. I supplied the parts and knowledge and instead of paying them, I took their family to the mountains for a week camping trip..
So I guess what i am trying to do is figure out the best way to approach this and utilize the help.