I have just replaced a snapped passenger side CV axle on an 86 GT with a 3.4 swap and a Getrag 5 speed. I drained the tranny fluid so that I can add all new GM Synchromesh fluid, as is highly recommended by so many on the forum.
I couldn't find the GM product locally so I ordered it from Amazon.
The picure of the label on the Amazon page simply states "Synchromesh Transmission Fluid". Upon receipt of the product I see that this label specifies it as "SAE 75w-80 Synchromesh Transmission Fluid". Different labels, but both labels have the same part number "10-4006"
I believe the original spec for the tranny was 5w-30 transmission fluid.
I swapped a Getrag into my 1985 SE V6 in 1999...used motor oil in the trans for 10 years. Then a friend told me about GM synchromesh fluid....starting using that and transmission shifted much better.
I would never use anything but the Synchromesh fluid- all of the "Tonda" guys now use it because it works so good.
I believe Pennzoil and a couple of other companies make the stuff at a cheaper price....
I swapped a Getrag into my 1985 SE V6 in 1999...used motor oil in the trans for 10 years. Then a friend told me about GM synchromesh fluid....starting using that and transmission shifted much better.
I would never use anything but the Synchromesh fluid- all of the "Tonda" guys now use it because it works so good.
I believe Pennzoil and a couple of other companies make the stuff at a cheaper price....
So, am I hearing that synchromesh is all the same and I am good to go with the 75w-80?
Originally, the spec was for motor oil.....so approx' 5W-30 which is typical of motor oils....The GM/Delco Synchromesh oil is a whole different animal- and was specifically designed to help manual transmission SYNCHROS work properly....
Originally, the spec was for motor oil.....so approx' 5W-30 which is typical of motor oils....The GM/Delco Synchromesh oil is a whole different animal- and was specifically designed to help manual transmission SYNCHROS work properly....
Can you post a picture of your bottle of fluid?
I just texted you a photo from my phone. I'll try to upload the picture here tomorrow if needed.
⚠️ Warning: Most car's Manual Trans oil Is Not "Gear Oil" & using GO can ruin them because have Braze/Bronze parts. Not just GM but many other brands. Because Most GO's have a lot of Sulfur & other additives that "eat" Braze/Bronze, plastic & other parts.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Originally posted by Rsvl-Rider: ... The picure of the label on the Amazon page simply states "Synchromesh Transmission Fluid". Upon receipt of the product I see that this label specifies it as "SAE 75w-80 Synchromesh Transmission Fluid". Different labels, but both labels have the same part number "10-4006"
I believe the original spec for the tranny was 5w-30 transmission fluid.
Did I get the right stuff???
The original spec did indeed call for engine oil.
Synchromesh has become a popular replacement. For good reason, it would seem.
I've got some of the Pennzoil stuff down in the garage. I'll check it later. It doesn't seem to be 75W-80, from what I can tell.
Reader's Digest version... Based upon the second article, I'd probably go ahead and run it. The worst that will happen is that it will suck, and you'll have to use something else.
[This message has been edited by Raydar (edited 12-24-2023).]
Rsvl-Rider: GM Synchromesh fluid, as is highly recommended by so many on the forum. / Different labels, but both labels have the same part number "10-4006" / Did I get the right stuff???
To answer your question, yes!
I believe There are 2 types of GM Synchromesh fluids; Standard and Friction Modified
You brought ACDelco 10-4006 which is 'Standard'
The bottle also has (GM) 88900333 on the label which is a SAE 75W-80 Synchromesh Transmission Fluid.
BTW - Some members also suggest adding a 4 oz. bottle of ACDelco 10-4003 / GM 88900330 which is a "Limited Slip Axle Lubricant Additive" to the GM Standard Fluid if your Getrag/Muncie which has the ‘rattle’ of the unengaged gears.
{EDIT}
quote
82-T/A: what does the LSD additive do?
I learn that the additive is also known as Friction Modifiers to reduce unwanted noise and wear.
The other GM Fluid is Synchromesh - Friction Modified which is part number 88900399 or ACDelco 10-4014.
I found a thread on 'Bob Is The Oil Guy' forum that discusses the difference between standard GM Synchromesh and Synchromesh Friction Modified which have the same viscosity. According to the forum, both fluids are 'Friction Modified', however the Friction-Modified version dosage has 5% more and has a friction additive for LSD clutch packs that require a GL4 fluid. The standard fluid lacks the friction additive.
------------------ Original Owner of a Silver '88 GT Under 'Production Refurbishment' @ 136k Miles
[This message has been edited by Vintage-Nut (edited 12-31-2023).]
Pennzoil Syncromesh all the way.. no need to to put LSD additive in….in fact I’ve never heard of that used in a manual. It for the clutch packs in a posi diff.
The '88 service manual for Getrag 5 speed specifies part number 12345349 or equivalent. I used Valvoline synchromesh which cross references that GM number on the bottle.
Firstly, I’m not an expert and merely searched the forum like Rsvl-Rider did…….
My research found that GM / Pontiac changed the manual gearbox fluid in 1988. {Technical Service Bulletin 88-7-17 titled “Proper Service Fluid For Manual”}
The TSB and countless PFF threads highly recommend GM Synchromesh Fluid intended to deal with shifting difficulty when the gearbox is cold and the biggest differences will be felt in the Getrag/Muncie.
And no, I haven't been able to locate an actual copy of TSB 88-7-17 {See this thread “4 spd manual transmission fluid? by Madess started on Oct-18-2005} https://www.fiero.nl/forum/...060811-2-067743.html
Since many manuals have similar construction, I imagine GM Synchromesh Fluid (which is compatible with non-ferrous metals) would also be applied to other gearboxes’ that the original fluid recommended 5W30 oil.
GM changed synchromesh part numbers over the years; The 'Newest' GM number is 88900333 for 'Standard' Synchromesh in the USA, which formerly was 12345349 {EDIT - Canada GM / ACDelco number is 89021808 for standard synchromesh}
And yes, many members like other brands of synchromesh 'better', however my research says that GM isn't the 'same' ......
As a side note, some members commented that synchromesh helped for smoother shifting, but the fluid didn’t help the Getrag/Muncie ‘rattle’ (vibrations) of the unengaged gears.
I've been tolerating the Getrag rattle for years in my Formula (although I hate the racket). I forget what oil I have in the transmission, although I believe it's synthetic 10w30.
From my January 2016 YouTube description...
quote
I wanted to get a video of the sound of the 2.8L engine in my '88 Fiero with the newly installed CompCam 1.6 roller-tip rockers, but it's difficult to hear much of anything else over the clatter of the transmission! The notorious Getrag rattle... ugh. For anyone not familiar with this rattle, it's "normal" with this 5-spd tranny, and the sound disappears when the clutch is depressed.
When stick trans is making noise just @ idle & out of gear...
Is very likely input shaft has bearings are "bad" or out of adjustment if can be adjusted @ all & oil type won't help much if any.
Many FWD GM sticks don't actually use crank pilot bushing/bearing often makes more problems because nothing but bearings in the trans centers the clutch disk & loads related to that.
Can also be iffy Throw Out Bearing as Hydro Clutches nearly always have the TOB touching the pressure plate "arms." Is Why This system have no clutch adjustment.
Patrick: Is it (Royal Purple Synchromax) thicker than the others?
GM Synchromesh Transmission Fluid is SAE 75W-80 Royal Purple Synchromax Fluid is 75W-90
"Synchromax is formulated with Royal Purple’s synthetic, proprietary Synerlecadditive technology, offering improved shift quality over a wide temperature range and reduced gear noise."
[This message has been edited by Vintage-Nut (edited 12-27-2023).]
I don't know where you got that from, but Royal Purple does not specify. Royal Purple states: "Royal Purple® Synchromax® is recommended for manual transmissions that specify an automatic transmission fluid or other light-viscosity oil."
Anything that requires 75W-90, RP recommends their MAX GEAR 75W-90.
[This message has been edited by cyrus88 (edited 12-27-2023).]
Since I installed the Getrag in my Fiero I've only used Synchromesh (Pennzoil brand) and it shifts like a hot knife in butter, very smooth and never clunky whether I'm at full swing or just putting around. I do have an aftermarket Quaife limited slip in it. No need for additive with this design.
Since I installed the Getrag in my Fiero I've only used Synchromesh (Pennzoil brand) and it shifts like a hot knife in butter, very smooth and never clunky whether I'm at full swing or just putting around.
My Formula's Getrag shifts smooth as well (with I believe, synthetic 10w30)... but that's never been my issue. It's that damn rattle while out of gear with the clutch out. Do you have the rattle?
I've mentioned this before, years ago... but my Getrag never had the rattle until I let someone drive my Formula at autocross. They were unfamiliar with the car, and did several high rev 3rd gear launches off the line... and that's all it took for the damn Getrag rattle to manifest itself.
[This message has been edited by Patrick (edited 12-27-2023).]
GM part # 12345349 I posted earlier crosses over to RP Synchromax on page 2 of link you provided.
Ah, sorry... I was using the updated GM part numbers listed later in the thread. Thanks. At least now we have confirmation that Royal Purple Synchromax is indeed suitable to use in place of GM / ACDelco Synchromesh Transmission Fluid.
I edited my posts above to response 82-T/A's question: "what does the LSD additive do?" as I can’t find the thread which recommends adding 'Limited Slip Axle Lubricant Additive' when using standard GM Synchromesh Fluid.
Also remember the 'other' GM Fluid too: Synchromesh - Friction Modified (GM 88900399 / ACDelco 10-4014) which standard GM Synchromesh Fluid have less of FM.
USA Photo of GM / ACDelco Synchromesh - Friction Modified Fluid
[This message has been edited by Vintage-Nut (edited 12-31-2023).]
