There has been alot of talk lately about how much power the 4-speeds can handle. I've broken all 3 versions behind my 3800SC Fiero and am sharing info for those who are curious.

1st breakage: 3:32 geared in the weak case - broke the teeth clean off of 2nd gear.
2nd breakage: 4:10 geared in the weak case - case cracked (bottom left-hand side)
3rd breakage: 3:65 geared in stronger v-6 case - broken blocker ring * cast inner piece.

* Not quite sure what to call it, but it's the inner & outer splined cast piece.

Just to head off the "you don't know how to drive a manual" people, I'm not going to explain that I don't shock-load or do burn-outs. I've logged over 240,000 miles on a single clutch with no problems in the past.

I'll post some info in a bit on what I've found inside each trans as far as gear ratios & such.

-Tim

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84 Fiero, 3800SC Series II,4spd manual
12.90 @ 108.9mph

Curious if you could shoot me a PM with your mods or maybe a link to a page that shows what you have done to the 3800sc? My goal is 12.9 and I'm an 84 chassis so I'm trying to ball park it.. Thanks!

OK, the interesting thing is this:

1st 3.53
2nd 1.95 *
3rd 1.24
4th .80 for the 3:65 and the 4:10. .73 for the 3:32

* here is the interesting part. Same 2nd gear ratio in all 3 trans but the 3:65 has larger teeth. Tooth count is as follows:

3:65 2nd gear 39 teeth input, 20 teeth output.
4:10 and 3:32 2nd gear 43 teeth input, 22 teeth output.

The diameter for all the 2nd gearsets are the same.

I know this differs from whats been posted before, but this is what I found in each of my trannies.

-Tim

If you really don't abuse the trany then I'd recomend checking for an alignment problem between the engine and trans.

Russ

no offense tim, butthats just about physically impossible, to log 240000 miles on a single clutch, no matter how rugged it is unheard of.. they arent physically designed to handle that much shifting, not even close.. unless you alway shift without the clutch.. and yes. the 4 speed is still the strongest of the fiero manual trannies.. the fact that you bust them up so frequently just tells me you DONT know how to shift, or you have REALLy bad luck with pulling bad trannies from yards for use in yrou swaps..

quote Originally posted by aaronrus: no offense tim, butthats just about physically impossible, to log 240000 miles on a single clutch.

I've seen many clutch go several hundred thousand miles. I've got a clutch job on a Mazda pickup booked for thursday that has 320,000 odd kilometers on the original clutch.

I have another customer that clocked over 800,000 kilometers on a Jetta with only 2 clutchs. There's more I'm sure I could list, but it is possable to get many many miles on a clutch.

[This message has been edited by jelly2m8 (edited 06-14-2005).]

quote Originally posted by TimGully: 3rd breakage: 3:65 geared in stronger v-6 case - broken blocker ring * cast inner piece. * Not quite sure what to call it, but it's the inner & outer splined cast piece.

have any pics? the block ring would only make it hard to get into gear - the actual "synchro" is what holds it in gear if thats what broke then it would pop out of that gear but the rear of the tranny would be fine.. the blocker rings and synchros do wear out and more prone to failign with age - thats about the only thing i'd see anybody braking on the 3.65 tranny which is why its the only one I REALLY trust - a good rebuilt 4speed with new synchros and blocker rings should hold up to most abuse - untill recently the last 4speed I had the blocker rings wore out so i had to revmatch every shift - since i had to match gearspeeds to well i actually stopped using the clutch when cruising around and only to speed up my revmatching when shifting faster.. the worn out tranny made a better shifter out of me

edit to agree on the clutch - I've NEVER worn out a clutch - never even came close - the only reason i've replaced them is for total failure - and they usually had almost brand new wear surfaces when removed

[This message has been edited by Kohburn (edited 06-14-2005).]

Oops, wasn't trying to imply the 240k clutch was on my Fiero. It was my 95 Grand Am. There is no reason not to go a few hundred thousand miles on a clutch because the only wear it gets is from 0-3 mph. No wear between gears if you RPM match.

Anyone have input on which 2nd gearset is stronger -- bigger teeth or finer mesh?

not to highjack this thread, but where can you find rebuild parts for a muncie from a 85gt?I have been looking because my syncros are done for

yeah, what fatmerk said. Where did you get yours Kohburn???

Bearings and seals are available at any parts store, and the synchros and blocker rings are still available from GM (albeit pricey). Last I checked, the synchro was ~$55 (need 4), and the brass blocker assembly ~$250 (need 2).

Marty

[This message has been edited by RacerX11 (edited 06-16-2005).]

quote Originally posted by TimGully: Oops, wasn't trying to imply the 240k clutch was on my Fiero. It was my 95 Grand Am. There is no reason not to go a few hundred thousand miles on a clutch because the only wear it gets is from 0-3 mph. No wear between gears if you RPM match. Anyone have input on which 2nd gearset is stronger -- bigger teeth or finer mesh?

bigger teeth assuming equal metallerigal properties..

quote Originally posted by Kohburn: bigger teeth assuming equal metallerigal properties..

That's also what I assume.

I can snap a pic of the part in question, but I've never used PIP. Would rather email to someone who knows how to post (volunteers ??)

Also for one of the other questions - It's not an alignment issue with the trans. I bolted the trans to the motor first and am using stock mounts. The housing cracked more or less directly underneath the shift/select assembly.

I should also add that 3rd & 4th were separate gears on my 3:65. I see some people have 3rd & 4th as one assembly.

quote Originally posted by TimGully: Anyone have input on which 2nd gearset is stronger -- bigger teeth or finer mesh?

I would also think that the physically larger teeth would be stronger, but for a different reason. It would seem that under really high power situations there would be case and shaft deflection and I would expect that the larger teeth would be able to handle a greater shift in alignment than the smaller teeth. You have to pull the smaller gears out a smaller distance before they are far enough apart to eat the teeth off of one another.

Kurt