GEARS or TORQUE CONVERTER?

PJ McCoy

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So i must have been a very good boy this year. I found lots a dough in my stockings,
(Thanks mom, dad, mother-in-law ((yup you read that right)) and wife)
Steel is ordered for the weld sub frame connectors.
And I can get gears or torque converter.
1..Gears: Ive never done it. Dont know what special tool i will need. Can they be rented? Whats needed to the job?
I want 3.55 i have 3.08 now posi. 8.5 10 bolt

2. Stall converter. Ive been reading about these since Ive been building the motor. Yank can have me one for 845.00. Custom for my ride. 5% efficiency losse at cruise. Tight on the cruise side and loose at W.O.T. they say stall will be 3200. For the top end. But still tight for cruise due to smaller diameter converter. 10 inch.
With 3.08 im at 2500 at 70mph. Doesnt look right to me.
Getting one built by ATI and rev max are around 350 ish. Both these companies said nearly the same thing.
22-2800 stall built tight in the middle ( how i dont know yet, waiting for email)
Based off my car weight, rear gear, estimated torque range from cam profile. ATI said 22-2600 and Rev Max said 24-2800. My concern is will the off the shelf type converter be ok. The custom converters are extremely expensive. Ive told everyone. Im not racing. I did mention a rear gear uprade in the future to 3.50 Yank was the only one who stated they back there converter and workmanship. Also that it would be just fine and would wake the car up later as well woth the gear change.

The rear gear calculator gives me a rear wheel torque multiplication of over 35% increase at the tire in final drive.

My thought was the torque converter getting me into the power range now and let the torque make up the difference for the 3.08.
I can change a converter easier than a rear gear. I also dig through craigslist to pick up a complete rear with 3.42 or 3.50/55 gear. Just havent seen any for $2-300.00 all day for 125 but 2.90 gears or less.

Whatcha think? Gear or converter.
Please explain to me why? Thanks
PJ
Edit: the rear gear increase was not 30% its 15% my apologies. I miss read the chart. You can see it in the post below.
 
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8ad-f85

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More gear will 'almost' feel like you have a new gear before your first gear, and first becomes second, etc.
(When the % equals the drop from gear to gear, anyways)
The cool thing about a good converter is that when it multiplies and begins to lock up, it will make 550 lbs torque feel more like 600 lbs.
There's no harm in a few hundred more rpm at 'flash'.
A 2800 converter won't 'slip' until 2800, making 2800 impossible to cruise at.
Doesn't work that way. Not supposed to anyways.
It will cruise much lower and depends on the efficiency of it.
I can't make a rec' or advise on price but I will say it does suck when the big Cad destroys your converter and sends the trash through the trans.
 

El Diablo

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What vehicle(s) do you drive?
1959 Cadillac Sedan deVille
If I had your car, I would strongly consider the 3rd and cheaper option. Making your ride lighter. My way of thinking is that there is really no down side to shedding some excess weight from your car. But mis judge your ring & pinion or stall speed for a custom converter and you will end up throwing your wrenches at the neighbors dog. Plus, weight is one of the variables to consider when choosing a converter. So to me, it makes sense to lighten first, then evaluate what you need in terms of gearing or stall speed.

But when you do get a custom torque converter, see if the maker will let you send it back in to loosen or tighten it up at no extra charge. Some companies do, some don't.
 

kzhurley

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10 billion+ 1/2 ton chevy trucks would have an 8.5 rear with 3.42,3.73 or 4.10 gears if you wanted to go the cheap gear route..
 
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dave brode

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Both.

If you really aren't going to race it [normal street rires only], on the cheap, you could find a 12" converter from a TH350. It will stall a few hundred rpm higher than a 13". Most of the cheaper street converters are 12", and will have a bolt pattern like a stock 12". You'd need an aftermarket flexplate, or drill the stock flexplate and weld washers cut to a "D" shape on the new bolt holes, as those holes fall on a ridge. Not spamming, but I have one for sale that is done that way. $50 and shipping.

I don't think that you need a $600-$800 converter. I would not be afraid of a known brand name 12" unit costing $200-$400. [I'd prefer a switch-pitch for any street car].

Ditto on the trucks for 3.42-1 gears. Older is better. New "2 cut" gears are hard to setup w/o noise. If you get all of the shims from the original donor rear with posi unit, you can almost always have good luck with swapping an oem gear set in the driveway. Not so with aftermarket gears, in most cases you need a pinion depth tool.

I would also look for a stock "S spring" posi, truck or car. That is the only good oem posi for the 8.5" imo. [get the side shims]

If you want 30 spline, you could buy C-clip axles for $259 from summit and buy a 30 spl posi. I'd look at an Eaton Truetrac, or Eaton posi [4 springs]. Note that the gleason/torsen type[truetrac] don't work well on ice/snow/mud, but they work well on dry road. https://static.summitracing.com/global/images/instructions/dtl-162c56a.pdf

I don't know enough about the "powertrax", monkey grip, or Richmond grip "S spring" type, or the purple spring eaton "style" [dishonest marketing imo] units to give opinion. [aftermarket eaton have yellow springs]

I would avoid Auburns or gov lock units, unless you got a next to nothing deal. You can find aftermarket Auburn in 28 and 30, not sure, but the gov loc may be 30 spline only.

Note that I was wrong on 33 spl posi units for 8.5". None available. The side gears from the 12 bolt 33 spline Eatons may fit the 8.5 eaton unit, but they don't offer the 8.5 units in 33.
 
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dave brode

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I did a search on identifying the 8.5"/8.6" carriers. I wrote that the "gov loc was the only posi in the 8.6 rear. Note that the last link states that there are three different posi carriers.

Here are some good links, note the Wallace site lists the casting numbers as ending in either 408 or 409, with the ...408 casting being for 2.73-4.10.

http://wallaceracing.com/carrier-id.html

Note that the Wallace site incorrectly lists the car 12 bolt carrier split. The OEM GM 3.90 gears fit the 4 series carrier, not the 3.

http://www.crankshaftcoalition.com/wiki/Rearend_identification#8.5_inch_10-bolt

http://www.crankshaftcoalition.com/wiki/Rearend_identification

It appears that I was wrong when I wrote that the "gov loc was the only posi in the 8.6 rear. Note that it is stated at this site that there are three different posi carriers.

"The 8.6″ axle was available with three different carriers: the “Large Window”, the “Large/Small Window”, and the G80 Gov Lock." I suspect that at least one of them would be a cone Auburn, maybe both.

It is also stated that 8.6 all have disc brakes, 8.5 have drum. note that a certain combo of bearings and races must be used to put a carrier from an 8.6 into an 8.5" housing. Note that an 8.5" carrier can not be used in an 8.6 housing. https://www.my4by.com/gm-10-bolt-8.5-inch-vs-8.6-inch.html

Note that until recently, replacement clutches for the square tab clutches for the S spring were unavailable. They are now.

I had forgotten: You can find gov locs that are converted to 4 spring style. The fragile governor parts are discarded, and install flat spring plates and 4 springs.
https://www.ebay.com/itm/REBUILT-SI...ash=item3adf21a3eb:g:bwoAAOxyTMdTNhm~&vxp=mtr

Here are links to the two different style Auburn units.
https://www.ebay.com/itm/GM-8-5-8-6...ash=item2396390f7e:g:KSoAAOSwbw1aHMvR&vxp=mtr
https://www.ebay.com/itm/Factory-Ch...ash=item520349c0a2:g:GKAAAOSwkLhZ79ir&vxp=mtr
 

PJ McCoy

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Dave this is good new. Quoted from the link https://www.my4by.com/gm-10-bolt-8.5-inch-vs-8.6-inch.html

The factory 8.5″ carrier when installed in a factory 8.5″ axle uses Timken bearing part # LM501349 and race part # LM501314. The inner diameter of the bearing is about 1.625″ and the outer diameter of the race is about 2.890″.

The factory 8.6″ carrier when installed in a factory 8.6″ axle uses Timken bearing part # LM603049 and race part # LM603012. The inner diameter of the bearing is about 1.780″ and the outer diameter of the race is about 3.060″.

Nowadays, most locker manufacturers produce parts only for the 8.6″ and include properly sized bearings to retrofit them into the older 8.5″ axles. Therefore, the inner diameter of the bearings for these parts will be about 1.780″ and the outer diameter of the race will be about 2.890″. This same logic also applies to differential carriers, but it is important to note that the parts are BACKWARD compatible only. That’s to say that the newer 8.6
″ differential cases when used with the appropriate sized bearings and races can install into older 8.5″ axles. As of this writing, there are no bearing and race combinations that allow an 8.5″ carrier or locker to install into an 8.6″ axle. When retrofitting an 8.6″ carrier (or a locker or a spool or any device that replaces the carrier) into an 8.5″ axle, it uses Timken bearing part # LM102949 and race part # LM102911.
Timken LM102949 Bearing
$10.59 (as of January 2, 2018, 7:33 pm) & FREE Shipping. Details $9.59

Helps maintain proper oil clearance
Reduces friction between two parts
Resists fatigue

Dave I dont know how you can find all this info. You amazing me!
 

CanadianC10

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Ive had good luck swapping gears, and swapping in and out shims on the carrier to get the right feel of lash - not tight and not too loose. I Even reused crush sleeves - my truck put on lots of miles and there was no rear end noise at all.
IF you really insist on spending money on a converter, Freakshow performance would be my recommendation.

Also have heard of an olds guy using a 4.3/th350 converter in his 455 powered C10 - said it performed better than his TCI converter.
 

PJ McCoy

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Ive had good luck swapping gears, and swapping in and out shims on the carrier to get the right feel of lash - not tight and not too loose. I Even reused crush sleeves - my truck put on lots of miles and there was no rear end noise at all.
IF you really insist on spending money on a converter, Freakshow performance would be my recommendation.

Also have heard of an olds guy using a 4.3/th350 converter in his 455 powered C10 - said it performed better than his TCI converter.
My flex plate is stock. So the bolt pattern is to small i believe.
Ive never installed ring and pinion. Also the specialty tools are not going to happen. I am going to change the rear gear only if i dont need special tools. Ive been reading alot and watching vids. Most vids leave out the important part. Setting the pinion depth.
Pick and pull has a 50% off sale starting on the 12 of Jan. Ill look there too for the gear and spaceres extra. The issue is, i dont know what looks bad except for the obvious broken tooth metal chuncks extea.
Pj
 

dave brode

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Non 2 cut Factory GM gears are very forgiving as far as setup. Difference between 2 cut and 5 cut:

You'll need a big pipe wrench or equiv to hold the pinion while getting the nut off. A 2 jaw puller is nice to pull the pinion, but you can bash iot off with a hammer] A piece of brass alum etc to nudge the pinion gear back out of the bearings. A BIG hammer and screwdrivers to bash the drums off if they are stuck.

Get the shims, noting which side each came from. You can usually get by just using the "new" R+P with shims that came from the donor rear. If swapping just the posi, you can normally get by keeping the shims that are in your rear. I say normally. It is possible that you could need a different amount of side shim to get the backlash and/or carrier bearing pre-load correct. With GM gears, just keep the shim that is behind the big pinion bearing on the "new" gears. Unless the pinion bearing is bad and needs replaced, you don't have to do anything as far as the pinion shim, as it's behind the bearing. .

You don't need a bunch of tools to swap GM gears. The inch pound torque wrench is good to measure pinion and side bearing preload. A $50 mag base dial indicator is nice for checking back lash [and cam degree work etc]. A $25 dial indicator would be nice to check tooth depth [2 vs 5 cut=]. The dial indicator can be used to check backlash in a pinch.

On pre-load = amount of drag on the bearings. On crush sleeve: It holds pressure between the pinion gears. A new one is only like $5, but they are really hard to crush. I have, many times, slide the old one over a piece of pipe or rod, and worked the hump with a hammer to lengthen the crush sleeve. If you make it .050"+ or so longer, it'll work. On carrier side bearings, the total amount of shim sets the preload there.

This sounds like hack, but I have swapped many GM gears sets, and only ever had two sets that made noise. One was a 3.73 truck 12 bolt gear. I moved them every which way and could not make them quiet. I suspect that they were setup wrong prior to me getting them, and were worn 'funny". The other was a ebay set of 4.33-1 car 12 bolt gears. They had a really odd look to the gear teeth. They howled like a fire truck siren. I suspect that they were run w/o lube an got hot. Shame, as they are hard to find.

 

dave brode

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Posi - turn wheels one turn, drive shaft revs = ratio
Non posi, hold one wheel, turn other wheel TWO turns, d-shat revs = ratio

When turning 1 tire [non posi], block the other so it can't move.

When turning both [posi], make sure both wheels turn exactly 1 turn. Worn clutches may allow one to turn a little more or less.
 

CanadianC10

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I installed the richmond 4.11s and mini spool in my old 8.5" rear with nothing but a 3/4" drive set, and a pipe wrench - like dave said.

never measured a thing - went by feel - a bit of pre load on the pinion and a bit of back lash on the gears. Did I get lucky? maybe - but I feel like unless your looking for that 3 hp you might lose without measuring everything - slap it together and enjoy it
 

Darius

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My flex plate is stock. So the bolt pattern is to small i believe.
Ive never installed ring and pinion. Also the specialty tools are not going to happen. I am going to change the rear gear only if i dont need special tools. Ive been reading alot and watching vids. Most vids leave out the important part. Setting the pinion depth.
Pick and pull has a 50% off sale starting on the 12 of Jan. Ill look there too for the gear and spaceres extra. The issue is, i dont know what looks bad except for the obvious broken tooth metal chuncks extea.
Pj
Reminds me of my old blind dates - and those were the Good Ones! :rolleyes:

d
 

PJ McCoy

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Dave. I think i can do this. I need to make sure i know how to tell the difference between the 2 types of gears. Im leaning towards the 91-96 caprice type GM cars. They were known to have 3.42 gears.
Cant remember the rest on the list. Also some early to mid 80s gm trucks used the 8.5 rear. Blazer/Jimmy full size did.
I saw a UTube vid. Show how to make a brace for the pinion yoke.
Thanks for your help
 
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