M1008 Transmission - Now Vacuum woes

[CivilEGR]

I had to send my truck to the shop when the transmission decided not to go into drive/reverse. They dropped the pan and and found out pretty quickly with all the metal that I needed a rebuild. I also had them do a few other small fixes that I didn't want to deal with myself and that completely blew my budget for my toys for 2022. I just got a call back from the shop saying they went for a test drive with the rebuilt transmission and it was shifting late and hard. They took it back in and checked the vacuum and found the pump was bad. They figured the pump being bad likely also contributed to the transmission failing. Now they're looking for around another $1K to replace the pump, lines, modulator. I really don't want to put another $1K into this. I had a pump from an old engine I could use, but my question is, can I replace the pump myself with the engine still in the truck? Or does the who top end need to be disassmbled and pulled?

 

[ezgn]

I had to send my truck to the shop when the transmission decided not to go into drive/reverse. They dropped the pan and and found out pretty quickly with all the metal that I needed a rebuild. I also had them do a few other small fixes that I didn't want to deal with myself and that completely blew my budget for my toys for 2022. I just got a call back from the shop saying they went for a test drive with the rebuilt transmission and it was shifting late and hard. They took it back in and checked the vacuum and found the pump was bad. They figured the pump being bad likely also contributed to the transmission failing. Now they're looking for around another $1K to replace the pump, lines, modulator. I really don't want to put another $1K into this. I had a pump from an old engine I could use, but my question is, can I replace the pump myself with the engine still in the truck? Or does the who top end need to be disassmbled and pulled?

Wow $1000.00 dollars! You can buy a pump head on Amazon for $75.00 dollars. A modulator for under $50.00 dollars. New rubber hoses, Under $50.00 dollars. About Two hours of work tops. Cardone Select 90-1008 new pump head at Amazon. If you need the entire pump Cardone 64-1200 $110.00 Re-built Amazon. Easy, simple job you can do your self. A simple vacuum check on the pump can tell you if your shop is correct.

 

[ssdvc]

THIS !. I just did all this myself, and with a really bad back and not great mechanical skills. With your new trans, after you do the above, she should run like new, mine did. And final adjustment is easy. Like Rick always says, "You can do this".

 

[CivilEGR]

The biggest question, do I have enough room to pull the vacuum pump straight out with the engine in the truck, or do I have to pull the manifold/fuel lines or anything else? Or do I need to pull the whole engine out of the engine bay?

 

[ezgn]

The biggest question, do I have enough room to pull the vacuum pump straight out with the engine in the truck, or do I have to pull the manifold/fuel lines or anything else? Or do I need to pull the whole engine out of the engine bay?

The pump comes right out with one bolt holding it in. One bolt at the base of the pump. Remove the air cleaner, grab a socket and an extension, pull the bolt, and pull the pump right out, easy. Use some The Right Stuff Sealant around the base of the pump for a good seal when you re-install.

 

[Squibbly]

The biggest question, do I have enough room to pull the vacuum pump straight out with the engine in the truck, or do I have to pull the manifold/fuel lines or anything else? Or do I need to pull the whole engine out of the engine bay?

It's probably the easiest job you will ever do on this truck. $1000 is someone taking advantage of you frankly, and I hate seeing that.
It's literally one bolt and it pulls out.
You'll need to pull the pod and seal off the pump you buy from Amazon, and you can replace the pod on the old one. Just use two bolts to attach it like the old one (not much of a choice actually).

You can twist the vacuum regulator to adjust your shift points, which is why you should check the vacuum yourself to make sure they aren't charging you 1k for a twist.

 

[CivilEGR]

Does anyone have a part number for a new modulator? What about the seals for the modulator and pump?

 

[Squibbly]

Does anyone have a part number for a new modulator? What about the seals for the modulator and pump?

See @ezgn response #2

This is the pump I bought and pulled the head and seal off of, and replaced the one on mine with.

https://www.amazon.com/Cardone-Select-90-1008-Vacuum-Pump/dp/B001PHKH46/ref=sr_1_1?keywords=Cardone+Select+90-1008&qid=1654343120&sr=8-1

This is the vacuum valve:

CHEVY GM AC DELCO 6.2 DIESEL VACUUM VALVE GM 14057219 | eBay

NOS GENUINE GM VACUUM VALVE.

www.ebay.com

This is the modulator:

https://www.amazon.com/gp/product/B007IAJFQ0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Modulators are personal preference. Some people like B&M, some people don't like the adjustable ones etc..

 

[ezgn]

Does anyone have a part number for a new modulator? What about the seals for the modulator and pump?

You have a Th400 transmission. Any 1984 K-30 Th400 transmission modulator search will bring up a lot of choices. B&M 20234 for $51.00 at Amazon is one choice. I think you are getting ahead of yourself on your parts search for the solution to your problem. Your vacuum modulator may be fine. Start to diagnose your vacuum pump first, What you need is a vacuum gauge. Under $30.00 dollars at amazon. Start with your vacuum pump, then your vacuum regulator. then you can move on to your modulator. You can replace all of your rubber hoses now if you haven't already. Then you can move on to diagnostics.

 

[ssdvc]

You have a Th400 transmission. Any 1984 K-30 Th400 transmission modulator search will bring up a lot of choices. B&M 20234 for $51.00 at Amazon is one choice. I think you are getting ahead of yourself on your parts search for the solution to your problem. Your vacuum modulator may be fine. Start to diagnose your vacuum pump first, What you need is a vacuum gauge. Under $30.00 dollars at amazon. Start with your vacuum pump, then your vacuum regulator. then you can move on to your modulator. You can replace all of your rubber hoses now if you haven't already. Then you can move on to diagnostics.

Like ezgn suggests, start with testing for vacuum from the pump. The TM lists testing procedures for vacuum at the pump and the modulator. Also check for vacuum at the transmission connection. My pump did not fail, but I replaced it as a precaution. However, my modulator did fail. After I replaced that, things still were not right. After some troubleshooting, I discovered a bad vacuum line going to the trans. Fixed that, and with some fine tuning, all was right with the world again.

Again, I am no master mechanic, but these repairs are fairly straight forward and once completed (and successful), they become skill and confidence builders as well.

 

[CivilEGR]

I ordered the pump from Amazon, and a new regulator. I don't think the valve is the problem, but I've also got a vacuum tester on the way. It might be a bit overkill, but I'd rather do it all at once than have to spend multiple weekends tinkering at it.

 

[ezgn]

I ordered the pump from Amazon, and a new regulator. I don't think the valve is the problem, but I've also got a vacuum tester on the way. It might be a bit overkill, but I'd rather do it all at once than have to spend multiple weekends tinkering at it.

It's common for the vacuum regulators to go out, so I think you made a smart choice. Since you have the vacuum gauge coming, I would test everything before you change parts so you know what the problem was. Like I said, change all the rubber vacuum hoses and then diagnose your problem. If it turns out just to be your vacuum regulator, put the new one on and save the spare parts until you need them. No sense taking off working parts and replace it with one that may not last as long as the one you have on there. The amount of time it would take to change the pump and regulator is 2 hours tops, not multiple weekends.

 

[DarkSeas]

See @ezgn response #2

This is the pump I bought and pulled the head and seal off of, and replaced the one on mine with.

https://www.amazon.com/Cardone-Select-90-1008-Vacuum-Pump/dp/B001PHKH46/ref=sr_1_1?keywords=Cardone+Select+90-1008&qid=1654343120&sr=8-1

This is the vacuum valve:

CHEVY GM AC DELCO 6.2 DIESEL VACUUM VALVE GM 14057219 | eBay

NOS GENUINE GM VACUUM VALVE.

www.ebay.com

This is the modulator:

https://www.amazon.com/gp/product/B007IAJFQ0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Modulators are personal preference. Some people like B&M, some people don't like the adjustable ones etc..

Well this helps me a lot haha - I was only finding ones for $120+, cheers.

Edit: I got the $65 dollar one and noticed after I ordered that the same seller has the same part listed for $45 so if anybody else is ordering one double check for the $45 ones first!!