Hey everyone
Been having this nightmare for a couple months now.

The symptom is that my car feels like its being completely held back.

DSM link shows the engine is running fine during this "hesitation".

I had a similar problem over a year ago and it was my rear calipers sticking.
I replaced those at that time cuz i noticed my rear rotors were getting warm.
The new calipers fixed that problem.

Little after that noticed my master cylinder was leaking, replaced that and car was good.

This winter is when I started having my recent problem. Same symptoms that the car felt held back, AND now my rear brakes were engaging before my fronts.
So I changed my proportioning valve and rear calipers again, and didnt fix nothing.

Thought it was my cat converter, so i changed my exhasut with another one i have, same thing.

I can put my car up so no tires are on the ground and everything spins freely.
(checked this cuz I also put a 4 bolt rear end in with a 22 spline tcase/tranny.
I dont know if this makes a difference but it came out of a 23 splined car? To my understanding the ratios are the same? or are they not? car was fine for a couple months after this swap.

Idling, my car has about 18 or so for vacuum.. When i pump my brakes on idle, they get super stiff, vaccumm goes to 10 and sometimes lower, and car starts to suffer and want to die. after driving for a bit my pedal also feels hard. I changed my vaccuum valve between IM and the booster, even tho i tested the old one and it seemed fine, changed it, still same thing.

To test my booster, I pumped my brakes with the car OFF, till they got rock hard, and pushed while i started the car.. the pedal slowly went down with ease but no where near the floor.

Driver side front and passenger rear rotors also get real warm sometimes, without applying the brakes.... Id downshift and pull over and feel the rotors.

I also did not drain my booster when I had a leaking master cylinder...
and at cruising speed, my car use to have vaccuum of about 15, now its at 10 on cruise load... 22 on decel while in gear..
Could my booster be bad even though it shows signs of being good? could it cause that section of brakes to stay on?
The MC's were identical when i swapped them, its a reman. from part source.. could it be for a 91-94? my car is a 90.. they looked the same like i said.. is there a difference at all?
Need help before this DSM goes down in flames! lol

Thanks in advance!

No one has any input??

Everyone is stumped!!

Maybe not everybody....

Did you bleed the air out of the entire system? Sounds like maybe you didn't..

Also you should do a boost leak test.

Put 2 bottles of fluid through it when I changed all 4 corner brake lines and the prop valve, but ill do it again and try it out.

I did a boost leak test a couple days ago and found my j pipe gasket was toast, fixed that up, but nothing from the booster.

Could extra air be getting sucked from the booster if its ripped?

Would be unregistered and leaning me out... My plugs looked good tho.

I was just thinking the performance problem might be a boost leak since your vacuum gauge symptoms match.

There might be some additional steps to priming the brake booster. I don't know the specifics but from casual reading I believe it is not so simple as to run new brake fluid through the master.

Not sure what priming a brake booster is?

And I was talking about bleeding the air out of the brakes..

I'm not sure either but "bench bleeding" comes to mind and here is some info..
http://www.dsmtuners.com/forums/newbie-forum/259623-master-cyclinder.html

How I understand its just putting fluid in before installing it to help from destroying the seals and less air to bleed out.. mines not leaking though, I had replaced a leaky one a while back and hasn't leaked since.

Have you changed your flex lines? They may be collapsed.

Yea I changed all for corners with ziggys braided lines

Im going to put a bottle of fluid through and flush the system

Ill post back after i try that

Bled them again and still no good, and fixed my boost leak at the j pipe, theres a little leak behind the TPS, not bad tho. I think its been there forever lol.
Went for a ride and didnt use the brakes.. Passenger front and driver rear were ice cold.. Driver front was a little warm and passenger rear was very warm..
Vaccuum still at 10 on cruise load, but im sure the engine is working jsut a but harder from behind held back from whatever it is!!.....

When i push the clutch to shift it feels free rolling again, then in gear hesitates.. its like my tcase is cooked or something....
Rear tires were locking up before the front in the winter time.. assuming the hesitation is from the rear..

Are master cylinders the same between ABS and non ABS?

If my brake booster was ripped would it suck air into it, and into the IM.. ?

Also activating my brakes with the extra air in the diaphram? .... heads spinning with questions.. lol

That sounds totally different than ANYTHING to do with brakes or boost leaks. That sure sounds like a drivetrain issue..

Yeah it does sound like drivetrain.
But FWIW, I've had situations where the car idles fine but doesn't want to go when it's in gear. It was a MAFS problem.

Based on what Kyle said about the splines and then Reza's comment (read: hint), I think I'd be doing some research into drivetrain compatibility
Amiright?

Kyle, I think your transmission output shaft is welding itself to the center diff, or your center diff gears shims are broken or seized, causing your rear wheels to have a mind of their own.

I bet the viscous coupling is burnt out already. Take off end case, remove VC clip, remove VC, turn over and if you see the inner plastic ring has been spat out from internally, then for sure its the center diff.

Either way, I would have just removed the tranny by now. Why has it happened ? I am not sure. You have not provided enough trans info.

Of course I could be wrong, and it might just be Fred Flinstone in the back of your car with his feet down

Yabbadabbadooooooooo!

Ziggy i was thinking brakes because my passenger rear rotor gets hot, and driver side front, when i dont even use my brakes and come to a rolling stop...my car will roll just fine idling and stuff, all tires roll free when its up on stands... also only seems to be hesitation when there is load on the engine.. like its sucking air into the brake booster activating the brakes a bit as it gets on the gas it brings in more air hesitating it more as the diaphram fills.. when my car idles my brakes are alot softer then after being on the throttle.

My tranny is from Tim Grech... was apparently a fresh build... hoping its not my tranny.. put a dent in the wallet getting that off him... over a year ago .. so its only seen 10000, 15 000 km, if that.

Im not getting any abnormal reaction from the car during cornering, and I can launch at 5500 rpm with a solid take off, no unwanted noise just spoolin.

Ive had a wheel bearing seize up before (mine are all new right now) but it almost feels the same... of course not pulling or anything.. you can feel that its powering through it and wants to go, but cant.. but when she hits 25 psi it powers through and goes like snot..

"reguardless of year, all the AWD transmissions have the same center diff. and final drive gear ratios" 90-96

From what I can find, the only difference in rear end ratios is between autos and manuals, and mine came out of a 92 manual into my 90.

Kyle, I was going to suggest wheel bearing as the cause of the warmth...but you say you have replaced them all?

I know you had brake booster issues, so maybe it IS something in that area? I really don't know...

Bearings are all good, I try and feel everywhere for heat.. Hubs, axles, diff, tcase, etc... but its just rotors. My fluid comes out smooth and clear, so I highly doubt its my brakes lines... BAHHHHHHHHHHHHH !!!!!!!!!!!!!! ARGGGAKJHFDAKH.... I have a booster in my garage from part source, but if I don't need it, that $350 would be nice to pay for what I do need lol

I just want to know if its possible to be sucking air from it.

Tried to have it fixed for the drags this weekend in Elliot lake. Prolly get beat by a neon if I tried

I would do as Reza suggests, pull the end case off the transmission and check out the VC and centre diff for problems. Will not take you long at all, and you don't need to remove the transmission or any major parts to check things out.

Even if it's just for peace of mind, it would be my starting point based on the problems you're describing.

Mike

Heading outside with my beer right now.. Ill post back later today.
Thanks guys

Makes me wonder how many dsm's are being wrenched on each day

VC is still in one big solid piece

If the center diff was bad, would it still hold back my rear wheels in neutral going down a hill?

Cuz it rolls fine down a hill with no load on the motor... its almost the more load the more it hesitates lol

Of course the VC will still be in one big piece. Flip it around and look closely at it, there is a plastic ring that spits out of it when it goes bad, from the side facing the bellhousing. Even if you don't see that ring it could have disintegrated. Look for a thick dark oooze that may have come out of the one side of it.

Yes a badly messed up center diff "can" cause the wheels to lock in neutral as well, depending upon how it is damaged.

How did your tranny fluid look ? dark and silvery ?

Its not the motor, the problem amplifies itself when you put load on the tranny and drivetrain.

No plastic at all anywhere, no oozing out of it, nothing between the 2 separate splines.

Oil wasnt overly dark, didnt smell overly bad either, and yes it had a bit of a grey shine to it.

Assuming my next step is to just take off the next part of the casing and actually just check it out? Will it show signs of being toast? Of course theres possible chance it wont, but does it normally? If so what am i looking for?

You might as well pull the center diff out too since your in there. It could still be pooched. Pull it out and open it up or check for broken seized spider gears, spin it and check the operation of it.

Alright ill go do that now.
What am I looking for in signs of wear? or can you not visually see it?
Back in 15 once ive got it out.
Thanks reza

Pull it out first, it should slide out easily. If it doesn't slide right out once you have the next case off, that means it overheated and most likely seized to the pinion gear. If seen that happen enough times.

The shaft that goes into the center diff is what grinds away at the spider gears from inside.

Pull it out and we'll go from there

Turns out I dont have a big enough socket to get her off.... lol



Heading to town to buy one from Princess Auto

What size do you need?

36 mm

Call my cell if you got it for me ill come meet you.. on my way to princess now tho

Biggest i have is 34 or 1 1/4.

center diff is out.. looks fine to me, spins freely in my hands

but then again, not sure how its suppost to be !

-Rear wheels don't want to turn going around tight low speed right or left turns.
-Nasty clunking coming from transmission area.
-Car feels like it's being held back, may even die, when trying to backup and turn left or right.
-Should be flakes of metal on the transmission drain plug.
-Likely to occur after a hard launch

.... I dont really even have the symptoms though, its only in a straight line when when Im on the gas, or in gear off the gas... Like i said it almost feels like a wheel bearings starting to seize..

"Thinking outside the box, sometimes brake boosters can develop vacuum leaks that are only exposed under hard braking, and then your engine would be sucking air brake booster vacuum line, and would run lean and could stall."

Found this in a post for a different car, but this is what I had been thinking was my problem.. with the hard peddle after accelerating, car dying if i pump brake, hesitation... SO gunna change that booster if this center diff isnt my issue... but how do i check my center diff??

If im in neutral rolling, does the transfer case still fully function? so i can cross that off the list? or does it some way some how disengage itself?

Well damn! You sure all the spider gears are intact and all ? They look fine through the holes, it spins smoothly, ?
Have you opened it up to check the upper and lower gear?

What about your transfer case, have you pulled it off and check to see if it spins freely ?

What about each drive axle, any up/down play in any cv ?

Do you still have the stock line with check valve in it running to the brake booster ?