1981 Pontiac Trans Am

Any questions or suggestions regarding restorations
Picard
Posts: 137
Joined: Mon 26 Sep 2011, 10:12

Re: 1981 Pontiac Trans Am

Post by Picard » Fri 02 Mar 2018, 12:35

I removed the gearbox, which was a pain in the arse. We really need a lift at the workshop as I'm getting to old for working under cars. My unique physique doesn't help the case much either :D

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The gearbox oil smelt quite bad and once removing the pan, I was surprised to see how much gunk was in there. The pan has a magnet to attract any filings etc, which was covered in black gunk.

After a bunch of disassembly, we landed up with a table looking like this.
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From what we can figure out, the gearbox suffered what is commonly known as ¾ Clutch failure. It seems to be one of the common failure points on the 4l60e’s.
We realised something like this could be the problem when we were trying to remove the input drum. It’s supposed to come out easily, but no matter how hard we pulled on it, we couldn’t get it out. Eventually…after a good couple of hard bangs on a piece of wood on the floor it came out.

Once we got the forward clutch pistons we found this.
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It seems, when this box was rebuilt, this seal may have been pinched. I’m guessing this would cause an issue with not enough line pressure, which will burn up the 3-4 clutches.

Picard
Posts: 137
Joined: Mon 26 Sep 2011, 10:12

Re: 1981 Pontiac Trans Am

Post by Picard » Fri 02 Mar 2018, 13:21

The clutches were in bad shape, all worn out and some heat damage.
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We tested the shift solenoids, which all came back fine.
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In the spirit of building this 4l60e properly, I’m importing a new solenoid kit as well as wiring harness.
I’m also importing a new Sun Shell. These apparently are very common failure points on the 4l60e’s and it’s recommended that they are changed out if you open the box. The one I removed seems fine, but I’m not up for taking the chance on it. I have no idea if it’s the original one that would have come with the box.

I opted for a Sonnax shell, which from all the reviews I’ve read is a decent piece of kit.
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Interspares in Troyville was a big help. I managed to purchase a repair kit from them which came with all the seals, clutches etc…. for the rest of the build. I also managed to source a new filter, band as well. I also decided to purchase a new reverse input drum, as I was not happy with the one that came out the box.
They’re also sourcing the clutch pistons from them.
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The torque convertor was removed. What a fun job that was. Stupid cars. That’s on it’s way to Full Race who’ll open it up and make sure it’s all ok.

I’ve been cleaning all the bits and getting them ready for when everything arrives.
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The pump has been stripped, cleaned and reassembled with new seals etc and is ready for fitment.
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Can’t wait for everything to arrive so that we can reassemble, hold thumbs, drink lots of beer and put it back in.

:cool:

Picard
Posts: 137
Joined: Mon 26 Sep 2011, 10:12

Re: 1981 Pontiac Trans Am

Post by Picard » Fri 02 Mar 2018, 13:22

Quick update.

Unfortunately I didn't take many pics of the assembly, but most of it was pretty self explanatory.

The torque convertor was sent off to Fullrace and two or three days later was sorted.

It always feels like Christmas when you receive boxes from the States. :D My Sonax Smartshell and new wiring harness with all the solenoids arrived safely.
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I compared my original sunshell to the sonax one, and they look pretty similar. The Sonax is supposed to be much stronger, heat treated and apparently stops spline stripping, hub breakage
and also eliminates planetary bearing failure and all in all seems like a good piece of kit.

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The kit came with the heavy duty reaction shell, thrust bearing as well as a custom roller clutch race
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Assembling the gearbox went well. We took our time, measured up everything and started putting all the bits together together.

The input drum was built up with all the clutches and measured out.
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We stripped and cleaned out the valve body. This one was quite tricky with lots of little parts.
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We finished assembling it and fitted the plates with all the check balls. 7 of them if I remember correctly. Once that was done, we carefully fitted the valve body, making sure we didn't mess any of the balls around.

Everything got torqued up to the specified amounts
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So this where the fun part began. We fitted the gearbox....bolted everything back together again and filled it up with oil. After a few hours on Saturday morning.....I finally got it ready to start and test.

With the rear wheels off the ground, we fired her up and ran her through the gears. Put it in reverse....nothing. Put it in 1st, 2nd, 3rd and Drive and it works perfectly. Try reverse again..... :'( Nothing.

So I start trouble shooting and eventually decided to hell with it and removed the gearbox....again.

During the build I had asked for advice from a gent who repairs gearboxes from home and I contacted him to ask him to help me check it out. He agreed and I took it through to him. I suspected it had been the reverse boost valve and he confirmed it. A dam circlip which we must have not seated correctly popped off and fell into the sump. >:(

While it was with him I gave him the go ahead to do a modification to the apply servo for better engagement on the band.

The box came back and I fitted it up again. Ran through all the tests and it's working perfectly now. :bravo_2:

Pulled the car out...gave it a nice wash and drove it home.

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On the highway she ran perfectly. Came off the highway, taking it nice and easy it ran through the gears without any issue. As I was about a block away from home, I noticed the temperature building. Pulled over and after a bit of investigation....figured out the Thermostat wasn't opening. :o and with the pressure it managed to blow off the bottom radiator hose. :angry:

Pulled out the thermostat, refitted the hose and got the car home.

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I've been wanting to replace the pump for safety's sake, so I did a bit of calling around to see if I could source a new pump locally without needing to order one in from the states. After a bit of help from the gents on the lumina owners whatsapp group, I managed to source an Airtex pump as well as a thermostat from the V8 Shoppe and fitted it last night. This weekend will spend some time testing it out.

One thing I will be fitting now, as a lessons learnt, is a CLD unit. (Coolant level detection). My brother supplies these units and had warned me to fit it as we normally do so on the old cars. This unit would have picked up that I had no water running through the hoses and immediately warned me about it. I was lucky enough not to damage anything.

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ZA Perana
Posts: 7125
Joined: Sun 15 Jul 2007, 18:01
Location: Cape Town

Re: 1981 Pontiac Trans Am

Post by ZA Perana » Fri 02 Mar 2018, 15:43

Very interesting post. The workings of auto boxes have always interested me and bravo for having the courage to rebuild one yourself!
Alfa GTV 3.0
Ford Capri Perana V8
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Wait not for tomorrow to do what can be done today, live each day for one knows not what the next day may hold.

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Chev58
Posts: 118
Joined: Tue 05 May 2015, 01:25
Location: Durbanville

Re: 1981 Pontiac Trans Am

Post by Chev58 » Fri 02 Mar 2018, 23:05

Nice work there Picard, done a few 4L60e boxes too - way too many parts in them hahahaha, for a bit of a performance build you should also look at fitting the Transgo HD2 shift kit(it makes a big difference over the std parts for shift firmness and quality and also fixes the 3-4 clutch failure issues in particular and is also supplied with heavier springs while you rebuild), good thing you replaced the sun shell & Rev drum - they wear out and fail on the splines as stated.
You should also closely inspect the 2 planetary gear sets, the bushes/bearings on the individual gears fail and could lead to catastrophic failure - upgraded planetary gear sets with 5 instead of 4 gears are available from USA suppliers.
Finally - get a proper tuner to re-calibrate the ecu transmission section shift points/speeds/firmness and diff/ tire sizes for correct(actual) speed references (this will fix your "hunting" issue you have and also make the gearshift correct) at various driving conditions.
Under normal city driving/cruising = smooth shifts you barely feel and in top gear od @ 60-70km/h.
Under aggressive driving/acceleration = it will squeal the tires at every gearshift :twisted: like a performance car should.
58 Chevy Apache

Picard
Posts: 137
Joined: Mon 26 Sep 2011, 10:12

Re: 1981 Pontiac Trans Am

Post by Picard » Sun 04 Mar 2018, 06:37

Thanks for the advice Chev58. I've put on about 150km since redoing the box and so far very happy with it. 8)

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TheQs
Posts: 64
Joined: Fri 07 Aug 2009, 09:19
Location: East Rand JHB

Re: 1981 Pontiac Trans Am

Post by TheQs » Sun 22 Apr 2018, 21:46

Absolutely stunning car sir!
"One man CAN make a difference!"

Neil Quantrill

1983 Pontiac Firebird
(K.I.T.T.)

Picard
Posts: 137
Joined: Mon 26 Sep 2011, 10:12

Re: 1981 Pontiac Trans Am

Post by Picard » Mon 23 Apr 2018, 19:24

TheQs wrote:
Sun 22 Apr 2018, 21:46
Absolutely stunning car sir!
Thanks man! We need to get some photos of the two together!

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