Had a friend install a 2 inch static drop on my 49 Ford now a test drive around the block it acts like it’s gonna shake itself apart. I think we need to get it up on a lift and see if the driveshaft is rubbing somewhere about the steel lowering blocks on eBay. They were listed as being for a Dodge Dakota, but they seem to fit right into place. They did not have any taper to them. I think I’ve seen somewhere that a 2 inch drop does not need a taper. I am wondering if my opinion angle has changed and caused this vibration. I believe I can find some wedges to put in there and here is my dumb question When lowering the car does that pinion angle need to drop down or maybe it has to be shifted up a bit I put in some 4 inch lowering box along time ago and they had a built-in taper. It’s been so long ago. I don’t remember exactly how those were installed Do you have any ideas? I bet there’s some sort of opinions number. This is now rubbing on is shoebox Ford is a pretty common custom car so I’m hoping somebody has run into this before.
Was the car lowered any already? If so, you will be lower now than just the 2" blocks. The short end of the lowering block goes towards the front and the tall end to the rear.
I've ran 4 inch no taper blocks on a shoebox in the past and had no vibration issues. When going over large whoops the u joint would hit its angle limit... a 2 inch drop shouldn't effect anything really... I'd check all bolts and nuts especially wheels if the vibration is at low speed.
Make sure the driveshaft isn’t now jammed into the back of the trans. It has to be at ride height to check it correctly
I had a car where the trans was level and the pinion was like 4 degrees down ... didn't vibrate at all. putting the pinion where it belonged did not change a thing. I don't see how blocks could change the pinion angle by much if at all.
Y,eah thinking about the way the vibration increased as a speed increased. I can see how that transmission/yolk deal could cause it. We will try to check that tomorrow.
Used and off E-Bay. Some blocks are made to move the housing for or aft to center a tire in the wheel opening. Look and see if your housing is now moved off the center pin some on one side but not the other, or some combination thereof. If the dowel hole and new pin head are offset, make sure they are both pointed the same direction.
If the blocks moved the rear end back, the driveshaft may now be too short, and not go into the transmission far enough.
Vibration, Front or rear? If rear , & all was installed was lowering blocks , Now Vibration, driveshaft to far in tail housing U joint & pinion angle changed, Needs to be checked @ road height ,with Weight on all four wheels , also rake changed so caster changed & check toe , Start with drive shaft bottoming out & check angle ,
Off set ? You referring to lineup pins Or Angle? With out seeing bottom more likely can redrill bottom to move forward or rear ward ,, Can make or purchase wedges for angle Change ,or & maybe adjust tail shaft up / down
I think the pins and holes are perfectly vertical. I’m not aware of blocks being offset to relocate the rear end, but I will check that. I have ordered a set of pinion wedges, just in case. I think the driveshaft being too long is the most plausible explanation. I will see about that in the next few days.
Rear tires on Early closed drive GM cars did not set centered in fender opening. You used to be able to get blocks that fix this when you converted to open drive and later drivetrain.
Is there any chance that the U-joints are now out of phase? It's been 60 years since I took a U-joint apart and back together, so I'm rusty about the details or if it's even possible to buckle them back up 90 degrees off. Maybe someone who knows can chime in with the right answer? Check both front and back pinion angles to see if they are in the same ballpark. 2 inches might not seem like much but if your original setup was on the feather edge of too many degrees of angle being off, 2 more inches the wrong way could shake. A short drive shaft will be impacted more by a particular drop change than a long(er) drive shaft will be. You could always take the blocks out just to test if it rides like it did before.
Pinion angle: At ride height the output shaft of the transmission has an angle, let use, for example, 2 degrees down toward rear. In the example, again at ride height, the angle of the differential pinion should be 2 degrees up toward the front. ( this would be 2 degrees down toward the rear, same as front). The trans shaft and pinion shaft need to be parallel. The universal joints take car of the rest. Article with diagram: https://www.hotrod.com/how-to/pinion-angle-change/
This is a common problem in the lowered car world and is definitely a problem in the mini truck world because they have a short drive shaft ( If I remember right a shoebox Ford also has a pretty short drive shaft. More than likely your pinion angle is now wrong and your u-joints are shot so it's letting you know they are bad. Unbolt the drive shaft and get an angle gauge Stick it on the rear end pinion snout If it is not flat fabricable something together so you can get a flat reading. You need at least one half of 1° to make sure the needle bearings rotate but you do not want more than 3° of pinion angle to get maximum u-joint life. Most vehicles you can usually get away with a little bit of a more severe angle without any noticeable drivability issues (My Ranger is probably 7° and it doesn't vibrate but my rear axle is also offset to one side which helps alleviate vibrations through the magic of science that I have no idea how it works). Also Your transmission and rear axle should be on the same plane or is at least as close as possible The professional drive shaft companies recommend I believe it's less than 1° difference. On every car I've had it's been way more extreme than that and I've never had any issues but again The tail shaft of the transmission and the pinion snout of the rear axle should be as close to in line as possible. Also if you have u-joints that are dry meaning they haven't been greased in who knows how long they will tend to bind up with even the slightest angle when under load and when the vehicle was stock you probably wouldn't have ever noticed this because It was riding in the same location for years Now that you've changed the angle it has a new location and it's not happy because it's not greased, The plus side is if that is the case it's super easy, You might get lucky and be able to regrease the u-joint (This usually doesn't fix it It's probably already damaged and wore out) or you might have to buy a new u-joint and if you do get one with a zerk fitting. Anyways it's pretty straightforward to paraphrase a maximum of about 3° on the pinion angle, Make sure that the U joints are in great shape, and Make sure the pinion and transmission are on the same plane and make sure everything is greased.
pinion angle ,,,, there should be a zillion posts here about its basically the front and rear ujoint angles need to match to cancel each others harmonics ,, getting it goofed up is common when lowering easlily remedied with wedges fabricator john miss you dad
No news. The car is sitting outside while I’m building a shop. I might be able to get it inside next week I really want to drive it soon
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