Getting a Z32 transmission to last?

[gbeaty]

About every 20 race hours, those little clips (I think they're called 'insert springs') on the syncros in our Z32 ChumpCar's transmission come off. Some get churned up by the gears so its hard to say how many come off, but the trans starts grinding more and more when going into gear. Typically 4th grinds first, and is the worst.

As we run enduros, we have to drive through the issue, causing further damage to the transmission.

We've replaced the clips on one transmission and it seemed to fix the issue (until they fell off again), so I'm confident the clips coming off are the root cause. I don't recall how the clips attach or what they do (my other team members do the rebuilds), but I'm going to look into safety wiring them on.

I just thought I'd check in here and ask if anyone else has had this issue, and what they've done to combat it? Anyone know of any good pics of the clips and how they attach?

[Seraphim38]

My 240 with 460whp had one installed and it had a bad input bearing from the start, which chewed itself and made loud grinding noises. I quickly bought a second 300zx trans with a warranty and from the first second of driving it would grind 4th gear no matter what RPM or speed I tried to shift at. So under warranty they gave me a completely rebuilt one with zero miles and it is super tight. So far I have had no problems.

I think the 96+ TT are the ones to get, but I can't confirm that from personal experience.

[jr_ss]

The 98+ is suppose to be the superior transmission with upgraded synchros. I just had mine rebuilt as well because I had the 4th gear grind woes as well. It should be good to go for awhile, atleast I'm hoping so...

[gbeaty]

We've never really damaged a synchro, at least not badly. After a 24 hour race we had both 3rd and 4th grinding badly, and a broken shift fork. When we loaded the car on the trailer it would not come out of 4th gear. Most or all of the insert springs had come out.

We opened it up, replaced the shift fork, insert springs and did not change the synchros. They looked alright. The transmission shifted well until the next race, when the insert springs came out again.

I suppose its heat-related as the problem never seems to occur on with 30-40 minute track sessions. Our car makes about 210whp; basically a stock NA Z32 with a few free tweaks.

1998 transmissions seem very pricey, and I'm not sure on their legality in our class. I'm going to try to find a way to keep those springs from falling out before trying a different transmission.

[Tower240sx]

does the Z32 trans have shift pads on the shift forks that are wearing? It seems from looking at the t5 (WC) which is greatly similar but different...that the "coupling sleeve" could over travel if the pads were worn, allowing the "shifting insert" to pass it's happy place and pop out or atleast rock enough to allow the spring to pop out. I remember playing with the FS5w71c (stock ka, sr etc) internals and having those pop out if I slid the coupler too far, when using the shift forks and shifter it wouldn't over travel in the same way.

do you have a factory shifter or an aftermarket unit? I'm tending tho believe this is an over travel situation on the part of the coupler, in other cars they need limiters for the throws on the shifter to prevent over travel, is there anyone in your group of drivers that "over shifts"?

you know the guy that has to cram it into the gear with no regard for feeling the transmission work through the shaft?

[Tower240sx]

does the Z32 trans have shift pads on the shift forks that are wearing? It seems from looking at the t5 (WC) which is greatly similar but different...that the "coupling sleeve" could over travel if the pads were worn, allowing the "shifting insert" to pass it's happy place and pop out or atleast rock enough to allow the spring to pop out. I remember playing with the FS5w71c (stock ka, sr etc) internals and having those pop out if I slid the coupler too far, when using the shift forks and shifter it wouldn't over travel in the same way.

do you have a factory shifter or an aftermarket unit? I'm tending tho believe this is an over travel situation on the part of the coupler, in other cars they need limiters for the throws on the shifter to prevent over travel, is there anyone in your group of drivers that "over shifts"?

you know the guy that has to cram it into the gear with no regard for feeling the transmission work through the shaft?

[gbeaty]

does the Z32 trans have shift pads on the shift forks that are wearing?

Doesn't look like it.

It seems from looking at the t5 (WC) which is greatly similar but different...that the "coupling sleeve" could over travel if the pads were worn, allowing the "shifting insert" to pass it's happy place and pop out or atleast rock enough to allow the spring to pop out. I remember playing with the FS5w71c (stock ka, sr etc) internals and having those pop out if I slid the coupler too far, when using the shift forks and shifter it wouldn't over travel in the same way.

The selector sleeve is definitely a bit worn, but not enough to let the clip out. The only way the clip could come out is if it was damaged somehow. You can pull the input shaft out a bit to make room to slide a clip in (as it is in the pic below), but presumably once the transmission is assembled its impossible for the shaft to move any significant amount.

do you have a factory shifter or an aftermarket unit? I'm tending tho believe this is an over travel situation on the part of the coupler, in other cars they need limiters for the throws on the shifter to prevent over travel, is there anyone in your group of drivers that "over shifts"?

you know the guy that has to cram it into the gear with no regard for feeling the transmission work through the shaft?

We have one team member who has historically "over-shifted", but we think he's gotten better.

The replacement insert springs finally came, so we put them on the 3-4 synchros tonight. Stock there are three pads on the synchro, and you use one spring per pad. However we doubled them up, with two on each pad. Will it help? I have no idea, but we thought we needed to try something. Maybe putting two springs side-by-side will keep them from moving around and getting smashed or something? We're kind of desperate at this point.

[KerryH]

Hey gbeaty, can you update us on this issue? Did doubling up help any?

[gbeaty]

Hey gbeaty, can you update us on this issue? Did doubling up help any?

The 3-4 shift fork was broken about 1 hour into the race. We think this was due to something getting stuck in the selector or sychro, combined with the driver pulling too hard on the shifter.

Evidently the insert springs cannot be doubled-up if installed correctly, as they go in the middle of the 'pad' on the synchro. We ddin't realize this, and installed them incorrectly. I'm not sure if this contributed to the failure or not; we've broken a shift fork before, and the springs always break and/or fall out anyway.