Help with drivetrain issue

[crembz Lurker Find all posts View Profile Close crembz]

Hi everyone,

Can anyone help me diagnose an issue I'm having with what I think is the drivetrain? Or recommend a good 4x4 mechanic in the south east of Melbourne?

The car is a 99 prado snowy. I bought the car @ 255,000ks and have put about 35,000kms on it in one year. I noticed the problem shortly after buying it.

When cruising @ 85-105 km/h in O/D (2000-2300 rpm) and under slight load up a slight incline, I get a low thumping which can be heard and felt through the driver floor and slightly through the steeringwheel. I also get severe slipping/banging if reversing up a hill.

I'm pretty sure the reverse problem is a torque converter issue, it's the cruising problem I'm trying to identify.

The thumping noise goes away if I back off the throttle.
Downhill at the same speed is all smooth.
All smooth in N downhill
Slight vibration from the tail coasting down in N
Applying brakes or handbrake makes no difference.
No thumping revving in N at a standstill
No thumping during stall test (at a standstill in D on the driveway)

Any ideas of what the culprit could be? Any help would be great, I'm trying to decide whether to repair (we don't really have any reason to get rid of the prado) or trade into a newer model but no idea what's wrong so no way of estimating a repair cost.

[carco Advanced Member Find all posts View Profile Close carco]

You seem to have a few different issues there so perhaps a visit to a trusted workshop is the go.
But before that I'd check the upper control arm bushes on the rear axle.
As the Prado is AWD, it's difficult to load up the drive train in order to check the various bushes, so a big bar is your friend.

[crembz Lurker Find all posts View Profile Close crembz]

A couple of things I've done which did not make any difference,

Tyres Changed and road force balanced
Prop Shafts balanced
Trans fluid and xfer case oil changed
Injectors cleaned

Oh and the car's on dual fuel, running petrol or gas makes no difference to the shudder.

Hi everyone,

Can anyone help me diagnose an issue I'm having with what I think is the drivetrain? Or recommend a good 4x4 mechanic in the south east of Melbourne?

The car is a 99 prado snowy. I bought the car @ 255,000ks and have put about 35,000kms on it in one year. I noticed the problem shortly after buying it.

When cruising @ 85-105 km/h in O/D (2000-2300 rpm) and under slight load up a slight incline, I get a low thumping which can be heard and felt through the driver floor and slightly through the steeringwheel. I also get severe slipping/banging if reversing up a hill.

I'm pretty sure the reverse problem is a torque converter issue, it's the cruising problem I'm trying to identify.

The thumping noise goes away if I back off the throttle.
Downhill at the same speed is all smooth.
All smooth in N downhill
Slight vibration from the tail coasting down in N
Applying brakes or handbrake makes no difference.
No thumping revving in N at a standstill
No thumping during stall test (at a standstill in D on the driveway)

Any ideas of what the culprit could be? Any help would be great, I'm trying to decide whether to repair (we don't really have any reason to get rid of the prado) or trade into a newer model but no idea what's wrong so no way of estimating a repair cost.

[crembz Lurker Find all posts View Profile Close crembz]

Yeah I hear you. I've never had a 4x4 before, only performance cars, so I'm not sure where to take it. The last person who looked at it mentioned that the sway bar bushings and rear trailing arm bushing needed replacing, but I'm not sure that's really going to solve the problem.

I know the xfer case and front diff are a little noisey, but again, mechanic didn't think it was the source of the issue. The driveshaft place that balanced the shafts suggested it was a transmission issue.

You seem to have a few different issues there so perhaps a visit to a trusted workshop is the go.
But before that I'd check the upper control arm bushes on the rear axle.
As the Prado is AWD, it's difficult to load up the drive train in order to check the various bushes, so a big bar is your friend.

[carco Advanced Member Find all posts View Profile Close carco]

Better get the big bar on all the rear end bushes then.
Worn trailing arm bushes will have the diff wandering all over the place when you power on/off and braking becomes quite unpredictable.
Worn upper arm bushes will have the universal flanges not running parallel which causes tail shaft vibrations.
The diff will really thump when the auto kicks down too, you'd think it wants to come through the floor.

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

Check your transmission fluid level. I think it's low and the cause for the slipping and banging when reversing up a slight hill. It'll only need to be slightly low too to wreak all kinds of havoc with every day driving. Check the transmission dipstick when the car is hot. The fluid should be in the hot range, which I think it won't be. Top it up and I reckon your transmission slipping and thumping in reverse will end. Does your car take a few seconds to find 1st gear again when you stop and then go to accelerate again immediately after, resulting in the transmission banging into first when you accelerate? If so, then it's definitely your trans fluid being a tad low.

To support Carco's comment about the bushes causing vibrations and so forth, do you get a ting noise when turning a corner, or feel the rear end clunk when turning a corner at lower speed. Do you also get a ting sound, noise or clunk in the rear end when going over a speed bump like something is loose? Bush replacement is expensive for a mechanic to do for you due to labour costs adding up. You'd be better off buying yourself a hydraulic press (a heavy duty one as alighter duty one won't cut it). Up to 6,000kg of force at times isn't enough and you'll need more. And do your research so you can replace all the bushes yourself one by one over the course of a few months. It'll save you a tonne and your car will handle like new. No need to buy new if you can't afford it, just buy a used one and then sell it on when you've eventually completed replacing all your bushes. If you plan to keep the car until it's racked up nearly 500,000km then hold onto it. Your mates and family may want to come over and use it themselves too to save some money. You'll become a bush replacement expert in no time.

Youtube videos of replacing bushes in 90 series Prados or Tacomas and 4 Runners to get an idea. YouTube at home hydraulic presses being used.

To aid in bush replacement, you'll need a half inch socket set or tool kit if you don't already have one and a 450mm and or 600mm breaker bar to get some of the bolts loose when removing parts. The socket set only has to be cheap. You'll probably just need to buy some extra correct sized sockets to suit your car as you do the work and come across different sizes bolts. Also buy a $40 mapp gas torch to help loosen frozen bolts and buy a $60 torque wrench to properly torque the bolts back up afterwards. Oh, and buy a Hayne's/Gregory manual for your car too which will help and lists all the torque specs.

[crembz Lurker Find all posts View Profile Close crembz]

Thanks for the info,

I don't get wandering when powering on and off but the car does seem to judder, wobble and shift direction when hitting a bump at speed. Tailshaft vibration is there when decelerating from 100 to about 85kmh, but it's pretty minor. No thuds or pings or anything unusual at low speed when turning.

Transmission seems to shift fine between gears, there's a minor thud when stopping and accelerating hard again but no hesitation.

The other thing i did was remove the rear prop shaft and drive on the front diff. This cleared up the vibration when decelerating but did nothing for my main issues, slipping in reverse and the shuddering at 85-105 in OD. The shuddering is a low pitched cyclical thudding, like a slow jackhamer, probably 4-5 times per second, thud .. thud .. thus .. thud ... thud felt through the driver's side floor pan and pedals mainly. Difficult to feel or hear this on the passenger side or in the rear of the car.

I'm thinking if the trans fluid top up solves the reverse slipping, perhaps I need to overhaul the entire suspension for the shudder @ 100kmh, every single squishy bush and damper. @300,000ks I'd imagine these things are probably stuffed. My concern is if after that expense it's something else, could end up being a bit of a rabbit hole.

I should have all the tools to do this myself but little to no experience working on suspension. I've done brake calipers/rotors before and various little bits in the engine bay, stuff I don't need a hoist for. Oh yeah, I don't have a hoist.

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

Rubber bushes are pretty cheap if you replace them yourself. A 20 tonne hydraulic press is between $200 and $300 on evilbay.
You will need to buy a few extra tools here and there as you go, but do it bit by bit as the budget allows. No rush. You'll need two spring compressors too for the front shock absorber strut when eventually replacing those bushes at the bottom eyelit. A trolley jack will speed things up expedentially. Supercheap just had a special on the 2 tonne one for $98 reduced from $180. But that sale is over now. The rear shock absorber bushes will require more time to change. The rear left shock absorber top nut is especially tuff to get a purchase on. Those two shock absorber bushes can take the pros a couple of hours to do.

You may discover when doing all this work your front end ball joints may need some attention as well. But only one way to find that out. I bought aftermarket tie rods with grease nipples which I was really happy to discover. So they're serviceable unlike sealed units which most of them are these days. Tie rods and ball joints will require some new tools that you most likely won't have. But all in good time. Research the related work that you plan to do on YouTube and you'll get an understanding of it. Research, research, research until you're comfortable with actually going through with it. Scroll through forums to get a gist of potential snags and brick walls a lot of people encounter and how they got around it.

[crembz Lurker Find all posts View Profile Close crembz]

Rubber bushes are pretty cheap if you replace them yourself. A 20 tonne hydraulic press is between $200 and $300 on evilbay.
You will need to buy a few extra tools here and there as you go, but do it bit by bit as the budget allows. No rush. You'll need two spring compressors too for the front shock absorber strut when eventually replacing those bushes at the bottom eyelit. A trolley jack will speed things up expedentially. Supercheap just had a special on the 2 tonne one for $98 reduced from $180. But that sale is over now. The rear shock absorber bushes will require more time to change. The rear left shock absorber top nut is especially tuff to get a purchase on. Those two shock absorber bushes can take the pros a couple of hours to do.

You may discover when doing all this work your front end ball joints may need some attention as well. But only one way to find that out. I bought aftermarket tie rods with grease nipples which I was really happy to discover. So they're serviceable unlike sealed units which most of them are these days. Tie rods and ball joints will require some new tools that you most likely won't have. But all in good time. Research the related work that you plan to do on YouTube and you'll get an understanding of it. Research, research, research until you're comfortable with actually going through with it. Scroll through forums to get a gist of potential snags and brick walls a lot of people encounter and how they got around it.

Thanks Mate,

I checked my atf today and found it at the right level, pink no smell. The shuddering in reverse still persists though, loud banging w/ momentary metallic squeals under load kinda like if you try reversing while the car is moving forward. Spoke to a mechanic about it, one thinks it's the torque converted the other thinks it's the gb. Either way seems like the box needs to come out. Is it worth rebuilding the box on these things or just salvage one from a junkyard? I keep reading the boxes are pretty robust so no idea why mine seems busted.

The Mrs and I really love the Prado, not too keen to get rid of it.