Transmissions and Drivetrain Need help with your trans? Problems with your axle?

7.5 rebuild plan ideas

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Old Aug 6, 2014 | 08:40 PM
  #1  
joshc's Avatar
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From: Watertown NY
Car: 1986 Trans Am
Engine: 350
Transmission: 700r4
7.5 rebuild plan ideas

I scored a 3rd gen rear end out of the junkyard with 3.42 gears to replace my 2.73 rear end in my T/A.
The gears look great, but I'd like to go through it with new bearings and seals before it goes in the car.
My overhaul plan is:
Weld axle tubes to center section
Timken bearings
All new GM seals
Ratech solid pinion spacer (crush sleeve eliminator)

Also planning on new rear brakes and shocks and u joints while it's all out.

Any other suggestions?
My car is not really wild. About 300hp and mostly street driven.
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Old Aug 6, 2014 | 08:51 PM
  #2  
big gear head's Avatar
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Re: 7.5 rebuild plan ideas

Welding the axle tubes isn't an easy job. You are welding steel to cast iron. This must be done right or it's a total waste of time. You must use nickel to weld these metals together, and there is some prep work that needs to be done before welding.

If it has 26 spline axles then they will probably break before you begin to slip the axle tubes. Upgrade to 28 spline parts if you are worried about breaking something.
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Old Aug 7, 2014 | 08:47 AM
  #3  
cosmick's Avatar
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From: North Salt Lake
Car: '86 Camaro, '94 Camaro, 3 others
Engine: LG4 ->L29, L32->LR4, L36, LG4, L31
Transmission: 700R-4, T5WC, 4L80E, SM465, 4L60E
Axle/Gears: 3.42, 3.23, WTB/WTT 2.93
Re: 7.5 rebuild plan ideas

As long as you keep the torque arm, then there's no reason to weld the tubes to the center. The ring gear will fail first. Once you go 28-spline, then the ring gear becomes the weakest link. And 300 HP shouldn't hurt the ring gear, unless you're doing clutch drops on race slicks.
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Old Aug 7, 2014 | 08:54 AM
  #4  
Chuck84TA's Avatar
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From: Woodstock, IL
Car: 1984 Trans Am Recaro Edition
Engine: 355 L98 Vortec 226/234 custom cam
Transmission: TKO-600
Axle/Gears: On borrowed time...
Re: 7.5 rebuild plan ideas

This may also be a good idea. Did this last year. So far, so good.

http://www.jegs.com/i/Moser+Engineer.../7105/10002/-1
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Old Aug 8, 2014 | 08:20 AM
  #5  
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Re: 7.5 rebuild plan ideas

Welding the axle tubes is an EXCELLENT plan, regardless of torque arm or anything else.

The tubes VIRTUALLY ALWAYS leak, the plug welds the factory puts in them are usually broken, and the tubes sometimes even are loose in the housing.

It is definitely true that welding them is a specialized situation; can't do it like Billy Bob sticking 2 pieces of angle iron together.

The rest looks fine.

I'd suggest a decent posi carrier (even if the one you got is posi, all it is, is an Auburn, and in case it still works at all, won't for long), having LCARBs installed while the welder is doing his thing, and a bracing type cover such as a TA Specialties. Maybe even get it powder-coated before reassembling it.

I would also suggest doing this ONLY to the best possible core housing you can put your hands on. That means, 90-up with disk brakes (28-spline, and PBR, not Saggy). That's really the important part. A set of gears is only $200 and you can have it on your doorstep tomorrow morning; an inferior housing is FOREVER.
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Old Aug 15, 2014 | 09:01 AM
  #6  
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From: PNW
Car: 91 Black Formula KR
Engine: 305 TPI R69/G92
Transmission: Astro A5-Pro 5.0-McCleod
Axle/Gears: US Gear 3.42 Eaton True Trac
Re: 7.5 rebuild plan ideas

to add to the above things...
Main Cap Bearing Stud kit, Aluminum 10 bolt cover...
I did all the things you mentioned, including Eaton True Trac, Richmond 3.42 gears, LPW Cover and Brace Kit, Factory 10 28 Spline axles, etc...

When it was getting switched out, I switched my aftermarket poly LCA's and Panhard bar for Founders 3 way poly joint ones and added the Spohn torque arm...

It rides amazing now, compared to the tired 150k mile stock rear end...

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Rafael
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Old Aug 16, 2014 | 09:26 AM
  #7  
Atilla the Fun's Avatar
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From: Northern Utah
Car: seeking '90.5-'92 'bird hardtop
Engine: several
Transmission: none
Axle/Gears: none
Re: 7.5 rebuild plan ideas

Originally Posted by sofakingdom
Welding the axle tubes is an EXCELLENT plan, regardless of torque arm or anything else.

The tubes VIRTUALLY ALWAYS leak, the plug welds the factory puts in them are usually broken, and the tubes sometimes even are loose in the housing.

I would also suggest doing this ONLY to the best possible core housing you can put your hands on. That means, 90-up with disk brakes (28-spline, and PBR, not Saggy). That's really the important part. A set of gears is only $200 and you can have it on your doorstep tomorrow morning; an inferior housing is FOREVER.
So much error here.
I'veyet to find the leaks coming from where the tubes meet the center casting, and I've seen more than you ever will. Don't you ever get tired of being wrong? Why do you even log in?
The '82 cores would actually be preferable to a '92, the casting molds and the machining were fresh in '82, worn out by '92. Spline count and brakes made no difference to the housing assembly. The only possible argument for newer is possibly fewer years and miles of abuse. Better to find a cherry '82 than a hammered '92.
And there's nothing superior about any 7.5" / 7.625", no matter the year or application. If you're going to the salvage yards to find an axle, find a 9" Ford. Older Ford large cars with 390s are still common, and those 9" aren't as thick ( excessively heavy ) tubes as F100 versions.
Any pure stock 9" in good condition, meaning fresh lube and new gaskets / seals, beats the best-built 7.625" on earth.
As for loose tubes: only if the car got slid into a curb. Broken plug welds? Not with the torque arm.
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Old Sep 8, 2014 | 08:02 PM
  #8  
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From: SC
Re: 7.5 rebuild plan ideas

Originally Posted by Atilla the Fun
So much error here.
I'veyet to find the leaks coming from where the tubes meet the center casting, and I've seen more than you ever will. Don't you ever get tired of being wrong? Why do you even log in?

As for loose tubes: only if the car got slid into a curb. Broken plug welds? Not with the torque arm.
my '99 ss rearend leaked around one axle tube, and my strange 12 bolt leaked around an axle tube.
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Old Sep 8, 2014 | 09:04 PM
  #9  
Formula 305's Avatar
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From: Saratoga Area, New York
Car: 1990 Formula Firebird
Engine: 305 TBI (LO3)
Transmission: WC T-5 out of an 88 T/A
Axle/Gears: 10 bolt, 3.42 & Torsen Posi
Re: 7.5 rebuild plan ideas

Atilla VS Sofa, let me get some pop corn, this is gonna be good.
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Old Sep 8, 2014 | 09:14 PM
  #10  
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Re: 7.5 rebuild plan ideas

Why do you even log in?
Why, to get insulted by people who haven't been around NEAR as long nor seen what I've seen, of course, and harbor deep resentments against those who have seen more than they have. Why else? Why are you on probation in the first place, anyway?, Kindness, sweetness, and light?

I have 2 cars with leaking plug welds sitting in my driveway RIGHT NOW. One, I could turn the tubes by hand in the housing. Needless to say, I've had em both welded up, by specialists.

I merely report what I see. If there's something you haven't seen yet, go get yourself some more experience, rather than insulting those who already have what you don't.
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Old Sep 10, 2014 | 09:21 PM
  #11  
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From: Watertown NY
Car: 1986 Trans Am
Engine: 350
Transmission: 700r4
Re: 7.5 rebuild plan ideas

The reason I wanted the axle tubes welded, my buddy's 84 z28 was starting to loosen up there and seep oil.
He flogged it in a burnout contest and cooked it anyways, but it would have been an issue soon anyways.
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Old Sep 11, 2014 | 05:52 AM
  #12  
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Re: 7.5 rebuild plan ideas

IMO it's a good idea.

It's important to make sure they are absolutely straight and rotated correctly... ya kinda only get one shot at it.
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Old Sep 11, 2014 | 08:27 AM
  #13  
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From: SALEM, NH
Car: '88 Formula
Engine: LC9
Transmission: 4L60E
Axle/Gears: 3.89 9"
Re: 7.5 rebuild plan ideas

Nickel or stainless rod and a TIG to weld the tubes. I wouldn't try with a MIG, no control over the heat.

-- Joe
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Old Sep 11, 2014 | 09:21 AM
  #14  
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Re: 7.5 rebuild plan ideas

Nickel is the only one that works. Stainless will not hold on cast iron.
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Old Sep 11, 2014 | 09:36 AM
  #15  
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From: SALEM, NH
Car: '88 Formula
Engine: LC9
Transmission: 4L60E
Axle/Gears: 3.89 9"
Re: 7.5 rebuild plan ideas

Originally Posted by big gear head
Nickel is the only one that works. Stainless will not hold on cast iron.
Nickle is brittle. Most guys doing structural steel to cast iron are using 309L now or silica bronze. I'm not too far from the shipyard, everyone and their grandmother is cast iron & steel welder here

-- Joe
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