Vacuum pump on a 1986 6.2L M1008

[L. H. Bridges]

I'm converting from a TH400 to a 700R4. It looks like the only thing the vacuum pump is connected to, is the vacuum valve on the injector pump that gives a vacuum signal to the TH400's modulator valve.

I've got the TV cable bracket for the 700R4 and am going to put in a switch for the lockup feature, so do I need the vacuum pump? I realize it drives the oil pump similar to a gas engine, but did any 6.2 L's come with no vacuum pump and some type of block off plate with a shaft.

Just trying to eliminate the stuff I don't need.

Thanks

[DmaxMaverick]

Welcome to the forums!

Your '86 vacuum usage should also include the HVAC system. Even if you don't have A/C, the vacuum still operates the heat/vent/defog. I'm not absolutely certain, being it is a M1008, but I haven't seen any allowances for a mechanically operated system.

You should check to be sure. Either check with key on/engine off, or engine on with vacuum disconnected. Turn on vent fan and cycle the vent selector through the positions. If vacuum operated, the air won't change from defog to vent to floor. Cycle it several times to ensure that any vacuum is depleated from the system. Try it again with vacuum hooked up and engine running.

An alternative to the engine driven vacuum pump, just to operate the HVAC, would be an electric pump. There are a couple of folks here that have done just that.

[G. Gearloose]

Pretty certain no ac on typical cucv's, ventalation control is via manual cables; Also, factory K20 trucks with no AC and 700R4, got J-code engines with no Vac pump and cable heater controls.

[Peter J. Bierman]

Not realy the anwer to your question but you can just remove the vacuum pod from the drive and block it off there.
Might be an option.

Peter

[john8662]

The only thing the vacuum pump was driving on my M1008 I was parting out was the tranny. To get rid of the vacuum pump all you need is a drive gear from a 6.5L. They are just a gear that has a mounting on the top that makes a near flush install, and still allows the cam to drive the oil pump.

[L. H. Bridges]

Thanks everyone.

I like the drive gear from a 6.5L idea, I'll see if I can find one.

This page is great, I've been reading it since November of 2003. All of my ideas and the solutions to my problems start with this page.

I removed the stock heater and replaced it with a vintage air conditioning unit assembly, so I couldn't think or find anything other than the TH400 transmission connected to the vacuum pump.

I just spoke to the machinist that I've been working with, and he is finished with the heads, block, crank, rods, pistons on the 6.2L so I'll start assembling the engine.

I've built several gasoline engines with him, but this will mark my first diesel engine.

You guys aren't kidding about the 6.2L being top heavy, I spun it around on the engine stand with the heads on, that will wake you up! I also was suprised to find the roller cam in the engine. A totally different animal to further my gearhead education.

The engine might be done in a month or two at my rate, (limited free time).

[EWC]

Casting number on mine is 26000036 . No sensor , just the oil pump drive .

[twaddle]

Hi LH,
Let us know how you get on and what you think of the 700R4 conversion.
I have a M1008 and with the 4.56 diffs and a three speed tranny is no laughing matter, so I'm thinking of going for the 700R4 route.
Also where did you source the transmission and other bits and bobs?

I've used my M1008 for about 8 years as a work truck as a Caterpillar mechanic and while they ain't the fastest they are strong, reliable old trucks.
Good luck.

Jim Twaddle jim@jimmyt.plus.com
Biggar, Scotland

[L. H. Bridges]

Jim,

I haven't bought the transmision yet, but I'll tell you what I've done so far.

Rebuilt the NP208 transfer case and changed the input gear to a 27 Spline. Bought the input gear and rebuild kit from rsgear.com

Input Gear, Part# 13948- $95.89
Bearing and seal kit, part# TK208- $81.25
FYI-drive chain, Part # HV-014,- $78.98

The input gear is one of the first gears you put in the case to rebuild, so to change it you need to take the transfer case almost all the apart. While I was at it I changed the bearings, seals and bushings.

I called Avant Salvage Company in Georgia, phone number 478-552-1901 for the transfer case adapter to fit the 700R4 to the NP208 transfer case (looks almost the same, but with four bolts instead of five). I also bought the TV cable bracket from him, it bolts on the back of one of the heads and connects to the injector pump. I think it was $35 for the adaper and $20 for the bracket.

Thats about as far as I've gone. I'll probably take forever on the engine.

When I get the engine in the truck I'll probably call Richard Berry and buy the 700R4 that fourth gear built for him (for sale in parts section), but I told him not to wait on me. If anyone else wants to buy it thats cool.

One last thing Jim, I go out of my way to specify and approve Caterpillar generator sets. I'm an electrical engineer and that is the one thing that I can always get current information on. The sales rep always help me out when I need info.

Later

L.H. "Chip" Bridges