straight cut gears
Launching!
Joined: Feb 2010
Posts: 285
Likes: 0
From: south florida
I'm starting to think those don't exist.
My trucks 4L80E came out of a 1999 3500HD tow rig, it doesn't have straight cut gears.
My friends dad bought a 88 GMC 2500 off the lot. I bought it in 2003 and rebuilt the th400 that had HD cast on the top. No straight cut gears.
I've had access to an abandoned hardparts shop when it was being cleared out for demo. I've seen literally hundreds of th400 gear sets, and none were straight cut. I even picked up a 12x12x12 box of sun gears, none straight cut. I found some rare stuff there like switch pitch parts, sprag type plantetaries, etc.
I've never even seen a picture of OEM straight cut gears.
My trucks 4L80E came out of a 1999 3500HD tow rig, it doesn't have straight cut gears.
My friends dad bought a 88 GMC 2500 off the lot. I bought it in 2003 and rebuilt the th400 that had HD cast on the top. No straight cut gears.
I've had access to an abandoned hardparts shop when it was being cleared out for demo. I've seen literally hundreds of th400 gear sets, and none were straight cut. I even picked up a 12x12x12 box of sun gears, none straight cut. I found some rare stuff there like switch pitch parts, sprag type plantetaries, etc.
I've never even seen a picture of OEM straight cut gears.
Teching In
Joined: Jul 2009
Posts: 13
Likes: 0
From: AZ
They did exist, but do to complaints about the whine in first gear they went to helical cut gears.
I've got two sets of straight cut planets sitting on the shelf.
They only came in extremely HD applications. 1 ton trucks didn't get them.
Motorhomes and other very heavy chassis.
Straight cut planets are actually weaker but they don't thrust load the pinion washers under extreme loads like a helical cut.
They only came in extremely HD applications. 1 ton trucks didn't get them.
Motorhomes and other very heavy chassis.
Straight cut planets are actually weaker but they don't thrust load the pinion washers under extreme loads like a helical cut.
TECH Regular
Joined: Mar 2009
Posts: 420
Likes: 0
From: Ricerville
Wouldn't straight-cut gears whine like a banshee? I think the transmissions used in some school busses was an Allison 545RE which had straight-cut gears. Those things whine! Would straight cut gears in an 80e do that?
i got a set. give me a call jim
Greg
Greg
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Thread Starter
Joined: Sep 2007
Posts: 4,188
Likes: 292
From: woodbine, md
Greg, i'll be down there Thurs or Friday, plan on stopping by, your about 30 mins from my sons-gonna drop off some stuff for the kid, gotta find out his schdule w/Nascar stuff first
TECH Resident
Joined: May 2006
Posts: 969
Likes: 119
Jakeshoe, you are the first builder that I have talked to that has ever admitted to the straight cut gears being weaker. Back in the early 1970's I found this out with M22 transmissions. They were noisy, slightly weaker and more costly than a good built M21 unit.
Dana,
You know me, I don't BS and I don't sell it either.
The straight cut planets have their place, but they are not needed or wanted in your average "hot rod" transmission.
Straight cut planets are
1. Easier and less costly to produce
2. Noisier
3. Prevent thrust loading
4. Weaker at the gear face due to less surface area.
Many builders assume that because they are "rare" or were only used in very heavy applications that they must be better, when the fact is, because they are cheaper, the OEMs would have used them more but they would have had customer complaints.
I only use them in monster trucks (due to the sheer weight of the truck at 10K lbs) or the motorhomes, etc they came in.
You know me, I don't BS and I don't sell it either.
The straight cut planets have their place, but they are not needed or wanted in your average "hot rod" transmission.
Straight cut planets are
1. Easier and less costly to produce
2. Noisier
3. Prevent thrust loading
4. Weaker at the gear face due to less surface area.
Many builders assume that because they are "rare" or were only used in very heavy applications that they must be better, when the fact is, because they are cheaper, the OEMs would have used them more but they would have had customer complaints.
I only use them in monster trucks (due to the sheer weight of the truck at 10K lbs) or the motorhomes, etc they came in.
Launching!
Joined: Feb 2010
Posts: 285
Likes: 0
From: south florida
You must have talked to alot of builders that do not do performance work or don't really know.I thought it was pretty much known that the straights are weaker than helicals,The fact that they are rare is the allure that alot of people want them and the assumption is that they are stronger.
