Sinking Creek 4WD Association

Over break i got a chance to drive my blazer a little around our house and the 700r4 trans is reallly sluggish. The trans does shift i got it up to 35 in my drive way but since i live off the high way no road test have happened. Also when you shift it into gear i can hear what sounds like metal clanking around while still in idle? And if you get on the gas too hard it will try to stall out, and did once.
I think that is the torque converter gone bad so i wanted to try just swapping another one out of the junkyard in to if it makes a difference.
What do yall think?

The metal clanking is probably slack in the driveline. Check rear u-joints and rear axle.

As for the stalling, I'd say the 2.8L isn't tuned real well. I'd check the timing and give the carb a good once over and lean drop.

It's a fair bet the fluid needs changed in it and it needs a shift kit installed to up line pressures.

One thing about automatics: They use power to turn the pump to create pressure. Small engines with larger transmissions, such as the TH700R4 which was used in everything up to 1-ton truck applications , have trouble creating the power required to shift them while moving the vehicle. This puts stress on the transmission and premature failure.

Personally, I'd look into a 305 TBI motor from a truck or camaro to swap in. While they are not power houses in the hot rodding world, they have their good points. The same stroke as a 350, but a smaller bore, means they make pretty good power. The L03 TBI 305 in my 89 Camaro gets ~30mpg on the highway at 70mph+. Also, you'd not have to be as worried about having too much power and breaking axles all the time. A V8 is fairly easy to swap in where a 2.8L is, I've done it! They make motor mounts, headders, and oil pans that make them basically drop in. With the A/C removed (how many of us actually use A/C anyways) and the radiator where the condenser was with a mechanical cooling fan, you'll have no heating issues what so ever.

The other option is a 4.3L. The motor mounts on those are a weaker design, similar to older vehicles (ask nick about motor mounts ) that tear apart easily and allow the motor to move around. Either way the transmission will have to be changed.

Our tahoe was making metal clanking noises at idle and could be heard (less evidently though) at other speeds. Turned out to be a bolt flying around the bell housing, mechanic said he sees it fairly often. Just an idea.

TerryD wrote:The metal clanking is probably slack in the driveline. Check rear u-joints and rear axle.

As for the stalling, I'd say the 2.8L isn't tuned real well. I'd check the timing and give the carb a good once over and lean drop.

It's a fair bet the fluid needs changed in it and it needs a shift kit installed to up line pressures.

One thing about automatics: They use power to turn the pump to create pressure. Small engines with larger transmissions, such as the TH700R4 which was used in everything up to 1-ton truck applications , have trouble creating the power required to shift them while moving the vehicle. This puts stress on the transmission and premature failure.

Personally, I'd look into a 305 TBI motor from a truck or camaro to swap in. While they are not power houses in the hot rodding world, they have their good points. The same stroke as a 350, but a smaller bore, means they make pretty good power. The L03 TBI 305 in my 89 Camaro gets ~30mpg on the highway at 70mph+. Also, you'd not have to be as worried about having too much power and breaking axles all the time. A V8 is fairly easy to swap in where a 2.8L is, I've done it! They make motor mounts, headders, and oil pans that make them basically drop in. With the A/C removed (how many of us actually use A/C anyways) and the radiator where the condenser was with a mechanical cooling fan, you'll have no heating issues what so ever.

The other option is a 4.3L. The motor mounts on those are a weaker design, similar to older vehicles (ask nick about motor mounts ) that tear apart easily and allow the motor to move around. Either way the transmission will have to be changed.

Why does the transmission need to be changed??

TerryD wrote:The metal clanking is probably slack in the driveline. Check rear u-joints and rear axle.

As for the stalling, I'd say the 2.8L isn't tuned real well. I'd check the timing and give the carb a good once over and lean drop.

It's a fair bet the fluid needs changed in it and it needs a shift kit installed to up line pressures.

One thing about automatics: They use power to turn the pump to create pressure. Small engines with larger transmissions, such as the TH700R4 which was used in everything up to 1-ton truck applications , have trouble creating the power required to shift them while moving the vehicle. This puts stress on the transmission and premature failure.

Personally, I'd look into a 305 TBI motor from a truck or camaro to swap in. While they are not power houses in the hot rodding world, they have their good points. The same stroke as a 350, but a smaller bore, means they make pretty good power. The L03 TBI 305 in my 89 Camaro gets ~30mpg on the highway at 70mph+. Also, you'd not have to be as worried about having too much power and breaking axles all the time. A V8 is fairly easy to swap in where a 2.8L is, I've done it! They make motor mounts, headders, and oil pans that make them basically drop in. With the A/C removed (how many of us actually use A/C anyways) and the radiator where the condenser was with a mechanical cooling fan, you'll have no heating issues what so ever.

The other option is a 4.3L. The motor mounts on those are a weaker design, similar to older vehicles (ask nick about motor mounts ) that tear apart easily and allow the motor to move around. Either way the transmission will have to be changed.

About the metal clanking in the drive line I get the noise as soon as i shift into gear and then it goes away. And the fluid looked dirty from looking at the stick, i planned to drop the pan over break but i was sick so it didn't happen. lol Also the PO had a shit kit installed about 50K ago so could that be the problem for it being so sluggish or could the pump have gone bad?

BadAssEddie wrote:
Why does the transmission need to be changed??

2.8L and 4.3L/SBC/BBC have different bell housings. Trans from 2.8L won't bolt to anything but 60* V6s and I4s.



About the clanking, is it a continuous clanking for a few seconds or is it just one or two clunks and then nothing? If the transmission was rebuilt improperly they could have left the anti-clunk (real name) spring out causing it. Could be slop in the t-case, bad u-joints, improperly setup or worn out rear ring and pinion, bad carrier/pinion bearings, bad spider gears, anything that will turn when put in gear as the brakes only hold the axle shafts.

No shift kit will cause the transmission to be sluggish. They all up line pressures and increase the apply pressure. The bad fluid could be causing it. It's possible that the shift kit upped the line pressure on the transmission to the point the worn out seals can hold it and allow it to blow by them. That would certainly do it. When you change the fluid, add some Lucas Trans-Fix (follow the instructions to the T), see if that helps.

will do. probably get home in two weeks or so got a lot of tests comming up and i'm not looking forward to putting a new trans in if i can help it .
And the clanking is just there for a few seconds along with a little kick when i shift it into gear. And the shift kit thats in it im told used to bark the tires shifting from 1st to 2nd.

jstables wrote:will do. probably get home in two weeks or so got a lot of tests comming up and i'm not looking forward to putting a new trans in if i can help it .

Well, here's some good news: If you can find a 305/TH700R4 (or even 4.3L or 350 ect) from a 80's vintage rig with a chain drive case, your t-case will bolt up to it. Then all you'd need is the proper motor mounts, headders, radiator, and a little moving/adjusting on the transmission crossmember and there you go. Could be easier to do with the front suspension cut out while swapping in a D44.

TerryD wrote:

BadAssEddie wrote:
Why does the transmission need to be changed??

2.8L and 4.3L/SBC/BBC have different bell housings. Trans from 2.8L won't bolt to anything but 60* V6s and I4s.

So you're saying that the 700r4 from his truck has a different bellhousing than the 700r4 off a V8?

Sorry for the hi-jack

yep
the v-8's are 90* except for the 305 which is 60* cylinder bores

TerryD wrote:
The other option is a 4.3L. The motor mounts on those are a weaker design, similar to older vehicles (ask nick about motor mounts ) that tear apart easily and allow the motor to move around. Either way the transmission will have to be changed.

Whats wrong with ratchet strap motor mounts?

Just be sure to have a very little hole in your transmission tunnel for the shifter so when the shifter moves forward and backwards with the detached drivetrain you notice before the motor smashes into the radiator.

jstables wrote:yep
the v-8's are 90* except for the 305 which is 60* cylinder bores

the 305's are 90* as well. If i'm not mistaken its just the smaller v6s that are 60* (the 2.8, 3.1, and 3.4) (my 2.5 I4 in my jeep is also the same 60* pattern)

edit: its just the smaller v6's that are 60* out of the chevy family, there are a couple other engines that use the pattern as well.

my bad your right dont know what i was thinking too much physics

jstables wrote: too much physics

Had that problem once!

As for V8's with 60* paterns, Cadillac made one in the late 70's. The 4.1L was an interesting little motor. If one could be found reasonably, that might make a sweet little engine to swap in the S-10. V8ish torque with gas sipping cubes. Not sure about mounting or any of that as I've never personally worked on one. Interestingly, there are two 3.8L V6s in the GM stable. One 60* and one 90* that the 4.3L is based on.