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Discussion Starter · #1 ·
So I decided this weekend to drain the tranny on my 91 s10 manual after I have been having some issues shifting it and alot of grinding noise when going to reverse.

I have the RPO=MY2 trans with the 4.3l v6 4wd.

I pulled out what looked like chocolate milk shake, except really thin.

Is this what the GM syncromesh fluid is supposed to look like or is there some other issue here.

From what I have read, GM says never to change the fluid, but that might have been the grossest looking fluid i've ever pulled out of a vehicle.

Anyways, for my driving and such I decided to go with a different fluid in the tranny, not sure what the outcome will be but either way i have a BW T5 sitting in the garage if i screw this one up.

I put 80W/90W gear oil and a friction reducer in the tranny. So far it shifts like a new truck. I swear I though the clutch or maybe the trans was going bad, but some new fluid seems to have made it all better.

Any thoughts on why the fluid would be so thin/terrible looking/performing?

Also what are the inherent risks to using the 80/90 with the FR instead of the $15/qt syncromesh?
 

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First off, if you are shifting in reverse seconds after being in a forward gear? Then its normal. i suggest you stop the the truck completely and shift into first to slow down the input shaft then shift into reverse with the clutch pushed down. i have seen what your trans fluid looks like. ever seen oil mixed with air like an egg beater while baking?? its normal. I would make sure you do your homework on what fluid you use. whether its gear oil or atf in your trans. I put atf in mine in my old blazer it quiet it down and the shift were smoother but i would still make sure it is gear oil or atf.
 

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Discussion Starter · #3 · (Edited)
Re: Q's about synchromesh

First off, if you are shifting in reverse seconds after being in a forward gear? Then its normal. i suggest you stop the the truck completely and shift into first to slow down the input shaft then shift into reverse with the clutch pushed down. i have seen what your trans fluid looks like. ever seen oil mixed with air like an egg beater while baking?? its normal. I would make sure you do your homework on what fluid you use. whether its gear oil or atf in your trans. I put atf in mine in my old blazer it quiet it down and the shift were smoother but i would still make sure it is gear oil or atf.


No, Im saying from a complete stop it would grind before when trying to put it in reverse. Like, start the truck in a parking spot, push clutch it all the way, and it would grind pretty hard as it shifted into reverse. Now It doesn't though.

And the specific fluid it says to use is "GM standard transmission fluid, P#12345349" aka GM Synchromesh. However I substituted for this in hopes of less grinding and cost.

And the trans fluid wasn't just the oil in air look. Heres a pic of how the fluid looked, although this isn't the specific fluid its really close to the color/look of the stuff I pulled out. It smelled pretty terrible too. and was really really thin, like easily thinner than ATF.

 

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first off getting the fluid from the dealer with a matching part number is the best idea so far. When ever i shifted into reverse i shift into 1st then reverse without releasing the clutch to get a smoother transition into reverse. if it grinds after you change the fluid you might have an internal problem with the syncros, shifter alignment or the idler gear for reverse is really worn.
 

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Gear oil is too thick. Use the specified fluid. Use the synchromesh with friction modifiers. You will only mess up the trany eventually. No matter what anybody says use the right fluid for the job.
 

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dont need friction modifiers in the trans. no friction material in trans, unlike
rearend clutches.
 

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I stand corrected. Based on this number he gave: 12345349 it is synchromesh transmission fluid. Non- friction modified. It is for the v-6's. The 4 cyl's use the friction modified fluid. I say again don't use gear oil.
 

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Discussion Starter · #8 ·
Ya seriously. The napa guy ****ed me and the transmission works like shit now.

And I have to change the trans fluid in the god damn snow.

****ing cranky now lol
 

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Definitely go with the correct synchromesh.
It has specified modifiers for a reason.
Don't feel like you have to use the overpriced GM product though. It isn't like they manufacture it or something.
 

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nothing beats GM specific Parts and Fluids. I buy AcDelco parts, GM Genuine Parts, and AcDelco Fluids buy the case on all the GM cars and trucks i work on the side. I get them at Cal's National Parts supplier through my boss. I love buying everything at cost even at PineBelt chevy.
 

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nothing beats GM specific Parts and Fluids.
Well, considering GM manufactures none of these, you're probably paying 50%+ just because the packaging has GM on it instead of the actual manufacturer (Champion, Warren, Hengst, Ashland, etc.).
 

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What size hex head wrench do I need to remove the plug on side of transmission. I need to check the fluid level in my trans. I wasn`t thrilled to read that the only fluid I can use is the overpriced dealer stuff.
 

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Discussion Starter · #14 ·
What size hex head wrench do I need to remove the plug on side of transmission. I need to check the fluid level in my trans. I wasn`t thrilled to read that the only fluid I can use is the overpriced dealer stuff.
Put the syncromesh from napa in, about 8 bucks a quart, huge difference though!
 

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GM Synchromesh is the sheeit!! I had grinding in a couple of old VWs ive owned and GM Synchromesh fixed all of them. The stuff is amazing. You can buy Pennzoil Synchromesh which I think is the equivalent but still I would pay the extra couple dollars for the ACdelco Synchromesh. Well worth it, and as you can see now, you already are going to be paying twice! ;)
 
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