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1993 Stealth R/T Twin Turbo
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Discussion Starter #1 (Edited)
So in searching issues with synchros I didn't see anyone asking about a way to work with the issue. So if the transmission shifts smoothly when rev matching then isn't there a way to have the rev matching happen all the time without having to be an expert at heal-toe shifting etc..

For upshifts there is the wide open throttle device to sty on the throttle the whole time without letting up and just use the clutch to shift. Not sure this kind of system can work to smooth out transmission wear for people not necessarily needing to be wide open all the time. Maybe it can work without full throttle.

For downshifts there is an auto blip product (it is for throttle by wire systems but just hypothetical at this point) that blips the throttle when the clutch and brake are used at the same time. Could this kind of logic be used for our cars to blip anytime the clutch is depressed (maybe with enough intelligence to not blip when the car isn't moving)? This should help with shifting up or down.Not sure blipping throttle on upshift works as this part is confusing (everything about blipping throttle is for down shifting which is easy to understand)

Or another possibility may be to slow the drop in RPM's when releasing the throttle (RPM drag) so that you can shift in time before getting out of the proper RPM needed to mesh nicely. This would be better than blipping in the sense that its probably easier to slow down the drop in RPM than the auto blip method.

The new cars with the rev matching transmission setups are probably ideal for prolonging transmission life. Not sure something like that could be built to work in an older car system without all the sensors already built in.

I'm not necessarily saying this should bypass needing synchros replaced but if it can nicely prolong those that are already toast and/or help them last longer on those that have been replaced then all the better. Looking at both long term and short term solution possibly. The thought of spending thousands of dollars on a transmission as general wear and tear seems excessive if it can be avoided for less (even if it cost a couple thousand to implement it would be cheaper long term).

Also thinking about making it easier for anyone driving my car, not just those who want to be masters at it.

Thoughts?
 

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1993 3000GT VR4
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Many of the current stand alone ECUs can control a DBW throttle body. I know the Haltech has adjustable throttle blip for downshifts and throttle follower (dashpot, to slow the RPM drop). Im sure many of the others (AEM, Megasquirt, etc) either have the same functions already, or could be made to do the same thing with generic timers/functions.

As for how to get a DBW throttle body, the 4G69 DBW throttle is a direct bolt on to the stock 3S manifold (I know because I am running one right now from a 2009 Galant with a Haltech Elite 2500).
 

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For upshifts you need to wait for the revs to drop, if youve ever driven a transmission with no synchro (semi truck). you wouldnt want a product that holds the throttle open. I owned a car where 2nd gear synchro was bad and it took all the fun out of driving one of these, 1st to 2nd is a huge deal in a 5 speed if you want to have fun! You also dont want the rpms to drop slowly if you are doing a quick shift. My car with a bad 2nd gear synchro I just had to time right, and that timing gets messed up if you drive slower or faster than you normally would once you get the timing down to not grind. Most people dont have this timing down because they are used to relying on the synchros and clutch, and basically shifts are very slow because the gear box only has 5 speeds. In a Semi you have 10 to 13, closer ratio so you can blow through 5 gears before youre doing 20mph lol.

Which gears are grinding for you?

Sorry for the edit, my semi truck tangent didnt really apply lol
 

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1991 VR4
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Try using 30W motor oil in the trans. This is what Kormex trans who rebuilt mine about 10 years ago put in, and they said to use only that. I once tried going back to redline and the shifting was much worse. Rev matching on downshifts is easy (just takes some practice). For the upshifts, double clutch (clutch in --> neutral --> clutch again --> into next gear) for easy shifts. I did this for several years on 2-3 shift and although you can't bang gears, you can still shift pretty quick once you get used to it.
 

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1993 Stealth R/T Twin Turbo
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Discussion Starter #6
Thanks for the info. I am grinding 1st to 2nd. Not if slow and steady shifting, just faster shifting. I just got here car so maybe the clutch or transmission fluid will be the cause as I haven't had it on the road much.

When I test drove it the problem was worse. I could even get into second without crunching. It was up north and was very cold so maybe the cold is affecting it as it's warmer here and works better.

My understanding of transmissions without synchros was to rev to a certain rpm or it wouldn't allow a shift so my thinking process would tell me I don't need the forms to drop quickly, I just need to shift when it hits the correct rpm so maybe a slower rpm drop would help.

The downshifting problem is always explained between the transmission side of the clutch and the engine side spinng at different rates when the clutch is pressed in and is hard on the clutch when it has to lock the two together. I get that but there is no good description of the synchros when upshifting and what it takes to make a smooth shift happen without the synchros having to grind.
 

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1991 VR4
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If the problem is 1-2 only, its probably the syncro, as other problems more universally affect all gears - cable adjustment usually affects side to side or forward to engagement (and corresponding gears), clutch dragging affects all gears, etc.

If the warmer weather improved your issue, you may very well benefit from the 30W oil change, as this would continue to thin the oil. Worth a shot IMO as it is easy to do, and you probably want to put new fluid anyways as a first step if you havent already.

I didnt really understand what you were trying to get at in your final paragraph but the synchros work the same way on both upshift and downshift - they sync the shaft speeds. When you are upshifting fast, they need to bring the RPMs down. When you are downshifting without rev matching, they need to bring the RPMs up. Same concept.
 
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