Need help choosing trans fluid to cure specific issue

[AlphaAssault]

Trans has about 35k miles on the rebuild. A few weeks ago, i changed the trans fluid - my first time doing so since i bought the car 5k miles ago - and discovered there was only a quart or so of fluid in the trans. I changed it because shifting had become notchy after warm and at low rpms (shifted fine at higher rpms, i.e. >5000). when warm and at low rpms, the shifter would actually stop in the middle between first and second, and i would have to wait before it would let me into 2nd. i put in almost 3 quarts of penzoil syncromesh and the issue persists; its a little better, but not much. its been about 500 miles since i put in the syncromesh. still shifts fine at higher rpms.

im looking to swap in a different fluid, but am unsure of what to go with. syncromesh seems too thin, because its acting just like it was when there was only a quart of fluid in the trans; not to mention it shifts better when its could; i.e. before the fluid has thinned out much. Im not sure about a synthetic trans fluid, people say its pretty slick, even the higher weight gear oils. i was thinking about regular 75w90 gear oil because its cheap and thicker than whats currently in there, but i dont want to keep buying fluid, so this time around i would like to get the best stuff for the job. ideas?

 

[ccb21]

Hey when you did the Fluid change did you change the filter? Sometimes that is a culprit in not shifting well at all, the Synco is good stuff should be fine

 

[AlphaAssault]

its a manual, so it doesnt have a filter. and, no to sound harsh, but syncromesh apparently isnt the good stuff, or at least not good enough, because its still difficult to shift. I think its just too thin, but i would like more opinions before i run out to buy more fluid.

 

[Lofty]

Syncromesh definately needs a warmup time, but that doesn't seem to be your problem.
Check your tranny mounting bolts. If your transmission is loose, it can cause loads of problems.
I put in syncromesh and it seemed like it was still hard to shift.
I checked my tranny, it was loose and just about separated from the engine.

So check that.
Also, have you adjusted your linkage?

 

[SD99GST]

^^^^ properly installed tranny is definitely important.

But when you talk about the synco fluid, do you mean Royal Purple's Syncromax. I think this is a very good transmission fluid. Used it on all my applications and cant say I have ever complained...

 

[AlphaAssault]

trans is snug against the engine and clutch is properly adjusted. im tellin ya, ive got it narrowed down to the syncros or the trans fluid, and since its not acting like worn syncros, that just leaves fluid.

also, im talking about penzoil syncromesh. thats whats currently in the transmission. its very thin, almost like normal 10w30 motor oil.

 

[SD99GST]

Well give the Royal Purple Syncromax a try...

 

[Steelnation36]

yea i have the penzoil syncromesh tranny fluid. Def not what i expected. I heard good things from a lot of people about it including john from shep trans but in my opinion i saw very very little improvement in shifting. I guess our cars will never shift smooth like a lot of other cars but i agree trhe penzoil may not be best. Im probably gonna flush the tranny fluid and try the royal purple

 

[AlphaAssault]

i dont mind a little notchyness, but this seems excessively notchy. it really takes you out of the driving experience when you have to stop and wait on a gear.

 

[Lofty]

i dont mind a little notchyness, but this seems excessively notchy. it really takes you out of the driving experience when you have to stop and wait on a gear.

Did you put too much tranny fluid in it?
I find it hard to believe that syncromesh made it worse.
Reason being, is my syncros are ####ed and syncromesh really helps.

 

[AlphaAssault]

Did you put too much tranny fluid in it?
I find it hard to believe that syncromesh made it worse.
Reason being, is my syncros are ####ed and syncromesh really helps.

syncromesh didnt make it worse; because before there was almost NO fluid at all in the transmission, and it was doing the same thing its doing now. syncromesh helped a little. syncromesh seems to be for transmissions that have a lot of miles on them. mine doesnt have many miles, so a thicker fluid i think would be preferred. which exact fluid is what im trying to figure out.

 

[Lofty]

syncromesh didnt make it worse; because before there was almost NO fluid at all in the transmission, and it was doing the same thing its doing now. syncromesh helped a little. syncromesh seems to be for transmissions that have a lot of miles on them. mine doesnt have many miles, so a thicker fluid i think would be preferred. which exact fluid is what im trying to figure out.

Well it seems you're past the break in period.
So I'd say go stock fluid, and if that doesn't help then use Redline MT90.
Syncromesh isn't really for old trannies. Shep recommends them in trannies if your build under 400hp. So I'd say your tranny wants some stock fluid. Or it could be worse and you could have ####ed the transmission by running it on low fluid, but I honestly don't think you did that.
Also you never mentioned if your linkage was adjusted, it makes things a whole lot less notchy.

 

[AlphaAssault]

Well it seems you're past the break in period.
So I'd say go stock fluid, and if that doesn't help then use Redline MT90.
Syncromesh isn't really for old trannies. Shep recommends them in trannies if your build under 400hp. So I'd say your tranny wants some stock fluid. Or it could be worse and you could have ####ed the transmission by running it on low fluid, but I honestly don't think you did that.
Also you never mentioned if your linkage was adjusted, it makes things a whole lot less notchy.

i dont believe there was any damage done to the trans due to low fluid. i baby the car; and there were no flakes or specks of metal in what fluid was in there. the trans doesnt grind at all, it just stops between shifts. and the linkage is tight and strait.

 

[Calan]

Whatever you go with, make sure the fluid is rated for tranny's with brass synchros (GL-4). The chemicals used in GL-5 rated fluids to provide the extreme pressure protection can be corrosive to brass or bronze synchronizers, which our's have.

Why was the tranny low on fluid in the first place? Mine is about to be rebuilt due to some gear lash issues; I tried several different fluids (including Pennzoil Synchromesh) and as expected it didn't make a whole lot of difference, except the thinner fluids seem to allow slightly quicker shifting.

If it is definitely hard to shift or grinding, I'd suspect you have some mechanical issues in the tranny or adjustment problems somewhere in the shifter/cables.

Edit:

When the tranny was rebuilt, did you go with double synchros or anything? Does it go from first to second smoothly without the car running? How is 5th and reverse?

It almost sounds like some kind of engagement problem with the 1-2 synchro/hub, now that I think about it some more. Shifter/cable issues (and an over-tightened reverse switch FWIW) usually affect 5th and reverse more than others. It's also possible that you had a cable/shifter issue and slightly bent a shift fork, although I think you'd see other symptoms.

 

[DougR]

Do the Skateboard bearing mod or whatever you guys wanna call it.

Even tho The bushings might not be the Actual Problem you have. That mod will Definatly make a Improvement.

 

[AlphaAssault]

Whatever you go with, make sure the fluid is rated for tranny's with brass synchros (GL-4). The chemicals used in GL-5 rated fluids to provide the extreme pressure protection can be corrosive to brass or bronze synchronizers, which our's have.

Why was the tranny low on fluid in the first place? Mine is about to be rebuilt due to some gear lash issues; I tried several different fluids (including Pennzoil Synchromesh) and as expected it didn't make a whole lot of difference, except the thinner fluids seem to allow slightly quicker shifting.

If it is definitely hard to shift or grinding, I'd suspect you have some mechanical issues in the tranny or adjustment problems somewhere in the shifter/cables.

what was your transmission doing to necessitate a rebuild? was it grinding, or what? mine is hard to shift at low rpms, but if i floor it, it shifts no problem. its very odd. ive read a lot of the threads on the trans fluid subject, and GL5 is certainly a no-no. right now, im leaning towards just the stock gear oil. its thick and non-synthetic, so that sounds like it would work.

 

[Calan]

what was your transmission doing to necessitate a rebuild? was it grinding, or what?

My initial problems a year ago were a rattling TB and worn input shaft which caused it to grind on decel. The first time, I had a local "expert" go through it and upgrade a bunch of stuff at the same time he was 'fixing" it (4-spider center diff, double synchros, torrington upgrade,etc.). After I put it back in, the grinding was even worse. So I pulled it again and tore it down myself, but couldn't find anything wrong with it other than some play in the input shaft .

After taking it to a real expert (which I should have done in the first place), it turns out that expert #1 didn't shim it correctly (it was off by .009"), so even though experts #2 did everything they could and fixed the clearance issues, the new gears were already worn and causing it to grind pretty bad on decel again. And I still had the rattling TB due to wear on the bell housing.

So instead of just putting in a new radiator and welding an exhaust leak last week, the project turned into putting the car on stands for the winter to pull/refresh the motor, rebuild the tranny completely, redo all my wiring, and reconfigure the firewall.

mine is hard to shift at low rpms, but if i floor it, it shifts no problem. its very odd.

Are you sure it's engine speed and not that you're just shifting harder when floored?

That is odd... still sounds like a synchro engagement issue to me, especially if it's RPM related. Different fluid may mask or ease the problem, but I think there is a mechanical issue there.

 

[AlphaAssault]

Are you sure it's engine speed and not that you're just shifting harder when floored?

That is odd... still sounds like a synchro engagement issue to me, especially if it's RPM related. Different fluid may mask or ease the problem, but I think there is a mechanical issue there.

there might be a mechanical issue, im not ruling that out. it just seems strange that it will shift perfectly fine under some conditions, and be excessively notchy under others. it never requires forcing the shifter into place, even when its being a pain, it slips easily into gear; when it decides to let me. it moves out of first easily, stops between first and second, then easily slides into 2nd. its that damn stop in the middle!

 

[SnowBird]

3 quarts is one too many, I dont know how you got 3 in there without spilling out unless your car was jacked up super high. I know what you mean about the syncromesh being thin. I did the cable bearing mod and it helped a little. Like you I didnt want to run straight syncromesh because of the thinness, I know run 1 quart pennzoil syromesh and 1 quart royal purple syncromesh. I still have the notchy feeling between gears like you describe, but I rest assured knowing I have good fluids in the tranny, if the fluid cant fix it and you put in the cable bearings its really out of your hands at that point, other than buying a new tranny. If it doesnt grind I wouldnt worry about it too much.

 

[RayBan GST]

i had the same problem and i just put a thick oil GL4 90w and its fine now ( the oil that i put is not branded its just local and now my problem is solved, however sometimes its hard to put it on second gear ( JUST SOMETIMES)


any GL4 oil 90w is your answer


good luck