Crazy Shudder

cruisinflatout · Nov 6, 2007

Crazy Shudder during Initial Acceleration (< 30 KPH)

I just bought an 89 Ranger 4x4. The guy I bought it from recently replaced the clutch and had the flywheel resurfaced but failed to replace the clutch slave while he was in there! The truck wouldn't shift into gear and the clutch tube (hydralic line) was cracked too so he dumped it.

Needless to say, I saved some cash by buying it in this condition.

I dropped the transmission this past weekend, replaced the slave and line and put it all back together. Changed fluids in the tranny (80w90) , transfer case (Mercon ATF) and rear end (80w90).

Now it shifts awesome but I have a pretty big shimmy anywhere form 0-30 KPH (0-20 MPH) and a slight vibration at all speeds.

I tried reversing the main driveshaft 180 degrees to no avail.

I read that a shimmy at first acceleration could be caused by the pressure plate not being torqued down properly. However, if I let the clutch out completely without acceleration, the shimmy is still there once I do hit the gas. The vibration also comes back when I decelerrate slower than 30 and it doesn't matter if I have the clutch engaged or not at the time.

I have also noticed some fluid splatter around the rear diff (looks old). Could this be a rear diff problem?

Any ideas on what the cause could be? Wrong fluids? Need Friction modifier? Need lube on driveshaft splines? Something mounted wrong (although I don't see how)?

Thank you for your time;

Kevin

Regina, SK, Canada
1989 Ford Ranger 4x4
3.9L 5 Speed Manual.

brendank · Nov 6, 2007

Regina eh? Cool. I'm in Saskatoon :icon_twisted:

Anyways, I'm kind of unclear as to the specifics of the vibration. Does it vibrate while running, but not moving? This would indicate a balancing problem somewhere before the transmission as the clutch and flywheel are rpm specific in neutral and not speed specific.

If it only vibrates when the truck is in motion, then it could be alot of things. I take it from your explanation that you never drove the truck before you bought it because it wouldn't shift? If that's true, then it could be unbalanced tires, bent rim, poorly balanced driveshaft, ect.

The fluids that you mentioned are correct, assuming you have a Mitsu trans and not a Mazda. There's an identification page in the tech library if you want to be sure, although it's quite a bit more likely you have a Mitsu.(And that's a 2.9, not 3.9)

cruisinflatout · Nov 6, 2007

brendank69 said:
Regina eh? Cool. I'm in Saskatoon

Anyways, I'm kind of unclear as to the specifics of the vibration. Does it vibrate while running, but not moving? This would indicate a balancing problem somewhere before the transmission as the clutch and flywheel are rpm specific in neutral and not speed specific.

If it only vibrates when the truck is in motion, then it could be alot of things. I take it from your explanation that you never drove the truck before you bought it because it wouldn't shift? If that's true, then it could be unbalanced tires, bent rim, poorly balanced driveshaft, ect.

The fluids that you mentioned are correct, assuming you have a Mitsu trans and not a Mazda. There's an identification page in the tech library if you want to be sure, although it's quite a bit more likely you have a Mitsu.(And that's a 2.9, not 3.9)

The truck only vibrates when in motion...it's not moter related. It has a pretty wicked shudder when you first take off and it seems to come from the rear end but it's hard to tell as it does shimmy the whole truck.

And 2.9L is what I typed wasn't it? :derisive:

I'm really leaning towards it being the rear end given the fluid splatter and slight leak at the yoke...it was about a half litre low on fluid when I first got it and who knows a) how long it was driven that way and b) what damage was done as a result.

Of course I plan to change the seal...but I'm wondering if the whole thing ain't toast...?

Is there anything I can do to determine which it is? How can I eliminate transfer case/driveshaft(s)/rear end one by one?

brendank · Nov 6, 2007

It's extremely unlikely that it's related to the transmission or transfer case.

First, I would do a complete check-over of everything. Pull on the drive shaft, checking u-joint play, looks for bent rims, ect. If you don't find anything, put the truck up on jack stands and take off the tires, and then put the truck in gear and see if the shudder still exists. By the way you explain it, it sounds like it's serious enough that you should still notice the shudder if it isn't a bent rim. (You can also swap rims front to back and see if the vibration moves) While it's spinning on the stands, check out the drive shaft to make sure it's as straight as you can tell, just by eye. Again, by the way you are describing the shudder, it's serious enough that it's not simply an out of balance shaft, more like a bent one.

If you get to that point and you still haven't found anything, I'd suggest pulling the diff cover off and doing a good inspection. Also, pull the axle shafts out and check to make sure they're ruined.

That's what I'd do, but there's many other ways to do the same checks.

4x4junkie · Nov 6, 2007

I agree, it sounds driveshaft-related by your description (u-joints, or out-of balance/out-of-round shaft).

cruisinflatout · Nov 6, 2007

Thanks guys...

I also forgot to mention that when I let off the gas from high speed (120kph) there is a weird squeal type sound that comes from the rear end? (At least that's where it sounds like it's coming from)

Sounds similar to one of the wind up type cars or motorcycles you had when you were a kid that you run across the floor a few times to get the wheels turning fast but every once in a while it gets out of whack and makes that noise and slows down right away? That's what it sounds like...doesn't matter if clutch is engaged or not...but it goes away under load.

haha...I have no clue if how I explained it will actually get anyone to know what sound I'm talking about though.

I will try the jackstand idea. Although some vibration may come from a bent rim, the truck has brand new tires and were recently balanced this past summer so I know they won't explain the shudder but perhaps may be responsible for some vibration.

Anyhow, thanks for the responses...I'll keep you posted. Let me know if you have any more ideas.

Kind Regards;

Kevin

cruisinflatout · May 21, 2008

Turned out to be the rearend, thanks for the suggestions and comments...

Hahnsb2 · May 21, 2008

Did you determine which transmission you have? You could either have an FM-146 or an M5OD in that year and they each take different lube, just thought I'd let you know even though your big problem was the rear end.

cruisinflatout · May 21, 2008

Yah it's got the FM146...it was definately the rear end. Upon further inspection, there was fluid spray on the underside of the box, but when I got it apart to change the seal - the rear end was definately toast. Bought a parts truck and she'll be good to go again soon after a quick afternoon swap.

Thanks;

Kevin

Hahnsb2 · May 21, 2008

cruisinflatout said:
Yah it's got the FM146...it was definately the rear end. Upon further inspection, there was fluid spray on the underside of the box, but when I got it apart to change the seal - the rear end was definately toast. Bought a parts truck and she'll be good to go again soon after a quick afternoon swap.

Thanks;

Kevin

Cool, Just make sure it's the same ratio if it's a 4x4 :icon_thumby:

cruisinflatout · May 22, 2008

Hahnsb2 said:
Cool, Just make sure it's the same ratio if it's a 4x4

Exact same rear end...both code 86 :icon_thumby:

Loanranger · May 24, 2008

I would double check that the u-joints are in phase on your driveshaft, if they aren't, and that's whats causing the vibration, it could also be what tore up your rearend if the vibration was bad enough.

cruisinflatout · May 24, 2008

Thanks, if there is any vibration at all once I do the rear end swap - I'll definately be investigating the shaft and anything else that might cause it.

It's looks like it was a long standing problem, there is splatter on the underside of the truck that looks like it's been there for a while...

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