dmd
Well-known member
I had my tranny rebuilt, but now it has this annoying whine in 1-3 from 2k rpm+. I don't know what the shop filled it with, but is this something that the right fluid can fix, or does it need more than that?
Best fluid for '99 T56?
- Thread starter dmd
- Start date
mikesgarage
Member
Hey brother
I read your post beautiful car.
That whine its usually from a miss placement of a shim.
Or a bearing might be bad.
Im going to lean towards a miss placement of a shim honestly.
I read your post beautiful car.
That whine its usually from a miss placement of a shim.
Or a bearing might be bad.
Im going to lean towards a miss placement of a shim honestly.
Hib Halverson
Technical Writer for Internet & Print Media
If the transmission is freshly rebuilt and it's making noise, a lubricant change is likely not going to fix anything, but...no harm in trying. The factory lube for a T56 is Dexron ATF.
That said, the first thing I'd do is go back to the shop which rebuilt it and complain about the noise.
gmjunkie
Well-known member
My $$$ is on the small tapered bearing on the left end of the top main output shaft shown below! It and the race in the input shaft are either rough or improperly shimmed!~!! That bearing is the only bearing in the whole transmission that is completely stopped in 4th Gear,thus "No Whine".
If there is a slight whine in 5-6 too,I'd be looking at the front input shaft bearing and race,and counter-shaft pre-load clearance (0.000-0.002 in) also.
Attachments
Last edited:
- Thread starter
- #6
dmd
Well-known member
Thanks to everyone for the suggestions. Junkie you're amazing, nailed it as usual. It actually does make the same noise in 5th, it just isn't as prevalent because of the 2000rpm minimum. I haven't had the chance to test it in 6th yet (har-har, who here knows how fast you have to go in 6th to hit 2000rpm?) I'll take this info over to them and see what they say - was just discussing it with the owner on Monday evening and he pointed out that same tapered roller bearing on a bench unit as a possible culprit.
- Thread starter
- #7
dmd
Well-known member
The other problem is first gear's engagement is stubborn. intermittently as I'm engaging it, It feels like it is going in about 3/4ths of the way then it either refuses to go any further and pops back out to neutral as I release the clutch (then grinds like an SOB going back in again) or takes excessive force to engage it all the way. Any ideas about that?
mikesgarage
Member
That is usually from a 1, 2 slider. What happens is the corners of the teeth become pushed in and rounded and it doesnt go through and let 1st gear ingage.
Maybe the shop didnt replace some of the parts you are having problems with?
Or like I said before a miss place shim could throw it out.
It probably pops out when you hit the gas when you take off?
And if the simming is wrong don't drive it you might be eating one of your hubs
Last edited:
gmjunkie
Well-known member
If it's that hard going into 1st. Have them re-adjust the the shifter as per GM SERVICE Manuel first,That may even take care of your whine,If the shifter isn't right it could be throwing a fork in a little bind and you might be hearing a blocker ring whining from another gear!
See this Post CLICK!~!!
Last edited:
LLC5
Well-known member
Like Junkie said start with the shifter adjustment first, if it is not adjusted properly it can affect the way the whole transmission works. It is performed in the console area inside the cabin and is easy to do. Good luck with it.
- Thread starter
- #11
dmd
Well-known member
The shop owner wants to try a different fluid that he's calling "Impact" by MTL. I did some googling and it looks like MTL is a Red Line brand, but there's nothing made by them by that name. He says it is a heavier oil that can even quiet a ZF. Anyone heard of this before? I'm concerned about doing damage to those paper blocker rings in the early T56's with any other fluid, plus I also feel like it's trying to cover up something that is wrong, like adding thick oil to an engine with rod knock. He doesn't seem to think it's a problem worthy of removing the trans to fix it, because he says his hearing's not so good and he can't hear anything and doesn't understand why I'm making a fuss about it.
Hib Halverson
Technical Writer for Internet & Print Media
Red Line MTL is a low-viscosity gear lube intended for use in modern manual transmissions. It works well in a T56, though it is recommended mainly for severe duty such as aggressive driving in the desert southwest or road racing.
If the transmission is noisy, it likely needs repair rather than a lubricant change, however, in some cases a heavier lubricant can reduce noise.
As for the shop owner insisting it's not a problem...if his hearing is not so good, how can he say the noise is not a problem? I'd get a second opinion and document it because you may end-up in an adversarial relationship with the first shop.
Last edited:
c4c5specialist
Technical Advisor
Hi there,
Just to be clear on this, the GM recommendation for fluid lubrication on the T56 has changed since 2006. The correct fluid is 88861800 and is a type of Dexron but it is NOT the Dexron 6.
Per engineering guidelines, there is something in the Dexron 6 transmission fluid that is incompatible with the T56 manual transmission.
MTL or a gear lubricant originally designed for manual transmission are thicker yes, but I have personally seen lubricant starvation on the roller bearings on which the gears on the mainshaft spin. The tight tolerances and the thicker fluid do not mix and the fluid doesnt lubricate adequately. This is one of the biggest reasons GM recommended the Dexron 3, which was the specification at the time of production when the original T56 came out.
Yes, MTL will quiet noises because of the viscosity, but will create other problems over time.
As far as the noise, the correct way to diagnose this concern is to use chassis ears on the vehicle and drive it. Localize one clamp at the input housing, one at each end of the bottom near the countershaft bearing front and rear, and one at the top near the mainshaft output taper bearing.
This will give you a definitive as to where the noise is the loudest and WHICH bearing is creating the noise.
And it will also tell you if the DIFFERENTIAL is also making any noise.
Allthebest, c4c5
Just to be clear on this, the GM recommendation for fluid lubrication on the T56 has changed since 2006. The correct fluid is 88861800 and is a type of Dexron but it is NOT the Dexron 6.
Per engineering guidelines, there is something in the Dexron 6 transmission fluid that is incompatible with the T56 manual transmission.
MTL or a gear lubricant originally designed for manual transmission are thicker yes, but I have personally seen lubricant starvation on the roller bearings on which the gears on the mainshaft spin. The tight tolerances and the thicker fluid do not mix and the fluid doesnt lubricate adequately. This is one of the biggest reasons GM recommended the Dexron 3, which was the specification at the time of production when the original T56 came out.
Yes, MTL will quiet noises because of the viscosity, but will create other problems over time.
As far as the noise, the correct way to diagnose this concern is to use chassis ears on the vehicle and drive it. Localize one clamp at the input housing, one at each end of the bottom near the countershaft bearing front and rear, and one at the top near the mainshaft output taper bearing.
This will give you a definitive as to where the noise is the loudest and WHICH bearing is creating the noise.
And it will also tell you if the DIFFERENTIAL is also making any noise.
Allthebest, c4c5
- Thread starter
- #14
dmd
Well-known member
gmjunkie
Well-known member
Don't do it!~!!!! After carefully inspecting "ALL" bearings,races,main output shaft and the inside of the gear journals,I'm satisfied lack of lubrication caused my problem after about 25,000 miles,To the tune of about $2900. my cost for parts!~!!
(But I did replace All torque tube bearings,bushings and installed a new LS7 clutch,pressure plate and flywheel while I was there!)
You'll end up with a bad case of "Blue Bearings" that a shot of penicillin won't help!~!!
Blow up my photo 200% and look at the bearings and the 3 bearing rolling surfaces at the rear of the shaft,They've been Very,Very hot! :eyerole
(Thats what Royal Purple recommended for C5's on their website at the time!)
:ugh
I went back with Red Line D4 ATF only because I could get it and the Chevrolet Dealer parts guy in my hometown looked at me like I was nuts and didn't stock GM#88861800!
10,000 miles so far and All is well!!~!!
Last edited:
Similar threads
Corvette Forums
Supporting Vendors
Dealers:
